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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Plan Name [Domain]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressPostalZipCode_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, Postal Zip Code</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cyd_CybersecurityRiskBoardCommitteeOrSubcommitteeResponsibleForOversightTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cybersecurity Risk Board Committee or Subcommittee Responsible for Oversight [Text Block]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PaymentOnRoyaltyAgreement_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payment on Royalty Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PaymentOnRoyaltyAgreement_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Payment on royalty agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PaymentOnRoyaltyAgreement_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Payment on royalty agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Recurring and Nonrecurring [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ScheduleOfCommonStockReservedForFutureIssuanceTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tabular disclosure of common stock reserved for future issuance, which may include but is not limited to outstanding options and outstanding warrants.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ScheduleOfCommonStockReservedForFutureIssuanceTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Common Stock Reserved For Future Issuance Table [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ScheduleOfCommonStockReservedForFutureIssuanceTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of common stock reserved for future issuance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityIncorporationStateCountryCode_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Incorporation, State or Country Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityIncorporationStateCountryCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Incorporation, State or Country Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenuesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenues [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenuesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenues:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Paid, Excluding Capitalized Interest, Operating Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash paid for interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PublicOfferingTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Public offering.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PublicOfferingTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Public Offering [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PublicOfferingTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Public Offering [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfOperatingSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of Operating Segments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfOperatingSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of operating segment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationTaxCredits_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation, Tax Credit, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationTaxCredits_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Federal and state tax credits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationTaxCredits_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Effective Income Tax Rate Reconciliation, Tax Credit, Percent, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationTaxCredits_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Federal and state tax credits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options exercisable at the end of the period (in dollars per share)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_BiopharmaCreditPlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">BioPharma Credit PLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_BiopharmaCreditPlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">BioPharma credit PLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_BiopharmaCreditPlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">BioPharma Credit PLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">US Government-sponsored Enterprises Debt Securities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Government-sponsored enterprise securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_GovernmentSponsoredEnterpriseSecuritiesDueInLessThanOneYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Government sponsored enterprise securities due in less than one year.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_GovernmentSponsoredEnterpriseSecuritiesDueInLessThanOneYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Government Sponsored Enterprise Securities Due In Less Than One Year [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_GovernmentSponsoredEnterpriseSecuritiesDueInLessThanOneYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Government-sponsored enterprise securities (due in less than one year)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenuePerformanceObligationDescriptionOfPaymentTerms_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue, Performance Obligation, Description of Payment Terms</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenuePerformanceObligationDescriptionOfPaymentTerms_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Revenue interest payments description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Hierarchy and NAV [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Hierarchy and NAV</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AtMarketIssuanceSalesAgreementsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">At Market Issuance Sales Agreements.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AtMarketIssuanceSalesAgreementsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">At Market Issuance Sales Agreements [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AtMarketIssuanceSalesAgreementsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">At Market Issuance Sales Agreements [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AuditorName_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Auditor Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AuditorName_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Auditor Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel2Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 2 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel2Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Level 2</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share Based Compensation Arrangement By Share Based Payment Award [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">STOCKHOLDERS' EQUITY</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock-based compensation capitalized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Amount Capitalized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_IncreaseInAllowanceForDoubtfulAccounts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase in Allowance for Doubtful Accounts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_IncreaseInAllowanceForDoubtfulAccounts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase in allowance for doubtful accounts.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_IncreaseInAllowanceForDoubtfulAccounts_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Increase in allowance for doubtful accounts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Maturity, Year Five</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">2028</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingOtherItemAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting, Other Segment Item, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingOtherItemAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Other segment expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TotalGrossToNetAdjustmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Total Gross To Net Adjustments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TotalGrossToNetAdjustmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Total gross to net adjustments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TotalGrossToNetAdjustmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Total gross-to-net adjustments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_MenloParkOfficeSpaceLeaseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Menlo park office space lease.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_MenloParkOfficeSpaceLeaseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Menlo Park Office Space Lease [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_MenloParkOfficeSpaceLeaseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Menlo Park Office Space Lease</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtCovenantMinimumCashBalancePercentageOfLoanAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of loan amount outstanding to be held as minimum cash balance under debt covenant.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtCovenantMinimumCashBalancePercentageOfLoanAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt covenant minimum cash balance percentage of loan amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtCovenantMinimumCashBalancePercentageOfLoanAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum cash balance as a percentage of loan amount outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Current Maturities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Less: current portion of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Long-Term Debt, Current Maturities, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtCurrent_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less: current portion of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_OperatingLeaseTermAdditionalPeriodExtension_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Operating lease term additional period extension.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_OperatingLeaseTermAdditionalPeriodExtension_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Term Additional Period Extension</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_OperatingLeaseTermAdditionalPeriodExtension_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease term, additional period extension</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CommercialPaperDueInLessThanOneYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents information pertaining to unsecured promissory note (generally negotiable) that provides institutions with short-term funds ), due in less than one year.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CommercialPaperDueInLessThanOneYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commercial Paper Due In Less Than One Year [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CommercialPaperDueInLessThanOneYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commercial paper (due in less than one year)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeasesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Leases [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeasesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">OPERATING LEASES</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">COMMITMENTS AND CONTINGENCIES</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_MunicipalSecuritiesDueInOneToTwoYearsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Municipal Securities Due In One To Two Years [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_MunicipalSecuritiesDueInOneToTwoYearsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Municipal securities due in one to two years member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_MunicipalSecuritiesDueInOneToTwoYearsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Municipal securities (due in one to two years)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ProductOrServiceAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Product and Service [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adjustments to reconcile net loss to net cash used in operating activities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangement and Arrangement Other than Collaborative [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Collaborative Arrangement and Arrangement Other than Collaborative</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_SiliconValleyBankMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Silicon Valley Bank.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_SiliconValleyBankMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Silicon Valley Bank [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Investment Owned, Fair Value, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Investment Owned, Fair Value, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owned, Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair value of equity investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employee Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Employee stock purchase</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cyd_CybersecurityRiskManagementProcessesIntegratedTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cybersecurity Risk Management Processes Integrated [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskByBenchmarkAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Concentration Risk Benchmark [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyPublicOfferingOfCommonStockAndWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">2020 Public Offering of Common Stock and Warrants.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyPublicOfferingOfCommonStockAndWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Public Offering Of Common Stock And Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyPublicOfferingOfCommonStockAndWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2020 Public Offering of Common Stock and Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_OptionTwoMinCashDebtCovenantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Option two min cash debt covenant.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_OptionTwoMinCashDebtCovenantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Option Two Min Cash Debt Covenant [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_TitleOfIndividualAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Title and Position [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue from Contract with Customer [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">REVENUE RECOGNITON</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale of Stock [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sale of Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentCarryingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentCarryingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Principal amount outstanding under term loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtCovenantMinCashUponLicensingTransaction_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Minimum cash covenant required upon certain licensing transactions being executed.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtCovenantMinCashUponLicensingTransaction_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Covenant Min Cash Upon Licensing Transaction</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtCovenantMinCashUponLicensingTransaction_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt covenant minimum cash balance upon licensing transaction</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionFairValueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionFairValueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of cash equivalents and marketable securities with unrealized losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_USTreasurySecuritiesDueInOneToTwoYearsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">US Treasury securities due in one to two years member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_USTreasurySecuritiesDueInOneToTwoYearsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">U S Treasury Securities Due In One To Two Years [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_USTreasurySecuritiesDueInOneToTwoYearsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">U.S. Treasury securities (due in one to two years)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Inventory, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Inventory</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Central Index Key</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Central Index Key</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CollaborativeArrangementCostSharingPercentageOfEntity_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the percentage of costs that Geron must pay during certain phases of the agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CollaborativeArrangementCostSharingPercentageOfEntity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangement Cost Sharing Percentage Of Entity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CollaborativeArrangementCostSharingPercentageOfEntity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of costs to be paid by Geron</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Available For Sale Securities [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheBMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tranche B [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheBMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tranche B [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheBMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tranche B [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Equivalents, at Carrying Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Amortized Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DirectorsMarketValueStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Directors&#8217; market value stock purchase plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DirectorsMarketValueStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Directors Market Value Stock Purchase Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DirectorsMarketValueStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Directors Market Value Stock Purchase Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AuditorOpinionTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Auditor Opinion [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Operating Capital [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Changes in assets and liabilities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsToBeGrantedToPurchaseShares_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the number of options to be granted to purchase shares in each year during the optionee's service on the Board of Directors.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsToBeGrantedToPurchaseShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options To Be Granted To Purchase Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsToBeGrantedToPurchaseShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options to be granted to purchase shares (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Concentration Risk [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, shares issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AtTheMarketOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">At The Market Offering Member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AtTheMarketOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">At The Market Offering [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AtTheMarketOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">At The Market Offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Minimum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Risk-free interest rate range, minimum (as a percent)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_MunicipalSecuritiesDueInLessThanOneYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Municipal securities due in less than one year.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_MunicipalSecuritiesDueInLessThanOneYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Municipal Securities Due In Less Than One Year [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_MunicipalSecuritiesDueInLessThanOneYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Municipal securities (due in less than a year)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_MunicipalSecuritiesDueInLessThanOneYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Municipal securities (due in less than one year)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Maturity, Year Four</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Statement [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PublicOfferingLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Public offering.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PublicOfferingLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Public Offering [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PublicOfferingLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Public Offering [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressStateOrProvince_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, State or Province</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressStateOrProvince_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, State or Province</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureAndSignificantAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureAndSignificantAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Warrant or Right [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_IssuanceOfCommonStockInConnectionWithWarrantExerciseShares_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number of new shares issued during the period in connection with exercise of warrants.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_IssuanceOfCommonStockInConnectionWithWarrantExerciseShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Issuance Of Common Stock In Connection With Warrant Exercise Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_IssuanceOfCommonStockInConnectionWithWarrantExerciseShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock in connection with exercise of warrants (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherAccruedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Other Accrued Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherAccruedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CostMethodInvestmentOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cost method investment ownership percentage.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CostMethodInvestmentOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cost Method Investment Ownership Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CostMethodInvestmentOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cost method investments ownership percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Concentration Risk Type [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_OperatingLeaseRentAbatementPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Operating lease rent abatement period.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_OperatingLeaseRentAbatementPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Rent Abatement Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_OperatingLeaseRentAbatementPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease, rent abatement period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CustomerConcentrationRiskMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Customer Concentration Risk [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CustomerConcentrationRiskMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Customer Concentration Risk</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional shares authorized (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Unrealized Loss Position</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total - Estimated Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ProceedsFromSaleOfFutureRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Sale of Future Royalties</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ProceedsFromSaleOfFutureRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from sale of future royalties.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ProceedsFromSaleOfFutureRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from sale of future royalties</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseCostAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lease, Cost [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseCostAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AccruedClinicalResearchOrganizationsAndClinicalTrialCostsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Carrying value as of the balance sheet date of obligations incurred through that date and payable for clinical related costs. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AccruedClinicalResearchOrganizationsAndClinicalTrialCostsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Clinical Research Organizations And Clinical Trial Costs Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AccruedClinicalResearchOrganizationsAndClinicalTrialCostsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">CRO and clinical trial costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Intrinsic Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options exercisable at the end of the period (in dollars)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyTwoPurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2022 Purchase Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyTwoPurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty two purchase warrants.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyTwoPurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Two Purchase Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DueToCounterParty_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Carrying amount as of the balance sheet date of obligations due to counterparty. For classified balance sheets, represents the current portion of such liabilities (due within one year or within the normal operating cycle if longer).</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DueToCounterParty_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Due To Counter Party</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DueToCounterParty_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amount due to Janssen Biotech, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LicenseAgreementDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">No definition available.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LicenseAgreementDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">License Agreement Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CoverAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cover</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CoverAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cover [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Earnings Per Share, Basic, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basic net loss per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Issuance Costs, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsGross_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Debt issuance costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Increase (decrease) in valuation allowance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DeferredTaxAssetsFederalAndStateCredits_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Deferred tax assets federal and state credits.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DeferredTaxAssetsFederalAndStateCredits_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets Federal And State Credits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DeferredTaxAssetsFederalAndStateCredits_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Federal and state tax credits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gross Unrealized Gains</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Expenses [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating expenses:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfConsecutivePurchasePeriodsInEachOfferingPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the number of consecutive purchase periods in an offering period in the purchase plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfConsecutivePurchasePeriodsInEachOfferingPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Number Of Consecutive Purchase Periods In Each Offering Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfConsecutivePurchasePeriodsInEachOfferingPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of consecutive purchase periods in an offering period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tranche one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tranche One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentAnnualReport_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Annual Report</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentAnnualReport_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Annual Report</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ConsolidationItemsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consolidation Items [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Unused Borrowing Capacity, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Available remaining loan principal under second amendment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock-based compensation expense included in operating expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Total stock-based compensation expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareOfCommonStockIssuedDuringPeriodSharesNewIssuesPublicOffering_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Issuance of common stock in connection with public offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareOfCommonStockIssuedDuringPeriodSharesNewIssuesPublicOffering_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock in connection with public offering (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareOfCommonStockIssuedDuringPeriodSharesNewIssuesPublicOffering_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number of new shares of common stock issued during the period in connection with public offering.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareOfCommonStockIssuedDuringPeriodSharesNewIssuesPublicOffering_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Of Common Stock Issued During Period Shares New Issues Public Offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Carrying value of term loan, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Long-Term Debt, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retained Earnings (Accumulated Deficit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated deficit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Retained Earnings (Accumulated Deficit), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Plan Name [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Plan Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tranche A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tranche A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tranche A [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balance at the end of the period (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Balance at the beginning of the period (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options outstanding (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalCashFlowElementsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Cash Flow Elements [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets, Current [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current assets:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Capital Shares Reserved for Future Issuance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, shares reserved for future issuance (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Common stock reserved for future issuance (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityExpirationPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit, maturity period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityExpirationPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Expiration Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Liabilities, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxLiabilities_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTotalLabel">Total deferred tax liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Deferred Tax Liabilities, Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided by (Used in) Operating Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net cash used in operating activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationForfeituresAndExpirationsInPeriodNet_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">The number of shares under options that were cancelled or that expired during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationForfeituresAndExpirationsInPeriodNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Forfeitures And Expirations In Period Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationForfeituresAndExpirationsInPeriodNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options cancelled/forfeited/expired (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RoyaltyExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Royalty Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RoyaltyExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Interest expense recognized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RoyaltyExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Payment on royalty agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ProductsAndServicesDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Product and Service [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accumulated Other Comprehensive Income (Loss), Net of Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Accumulated Other Comprehensive Income (Loss), Net of Tax, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated other comprehensive gain</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseTermOfContract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Term of Contract</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseTermOfContract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease, initial term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Concentration Risk [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLossCarryforwards_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net operating loss carryforwards, expire beginning 2028 through 2041</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLossCarryforwards_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Loss Carryforwards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLossCarryforwards_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Net operating loss carryforwards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property and equipment, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Property and equipment, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, Year Four</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2028</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided by (Used in) Operating Activities [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash flows from operating activities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsRecurringMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Recurring [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsRecurringMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Recurring basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyFourPreFundedWarrantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Four Pre Funded Warrant [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyFourPreFundedWarrantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty four pre-funded warrant.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyFourPreFundedWarrantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2024 Pre-funded Warrant</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CorporateNoteSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Corporate Note Securities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CorporateNoteSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Corporate notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of financial instruments measured at fair value on recurring basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Par or Stated Value Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, par value (in dollars per share)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cyd_CybersecurityRiskManagementPositionsOrCommitteesResponsibleTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cybersecurity Risk Management Positions or Committees Responsible [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Other comprehensive loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net unrealized loss (gain) on marketable securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TradeAndOtherAccountsReceivablePolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounts Receivable [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TradeAndOtherAccountsReceivablePolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts Receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfCashFlowsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Cash Flows [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CounterpartyNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Counterparty Name [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CounterpartyNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Counterparty Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtInstrumentFloorRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Floor Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtInstrumentFloorRate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt instrument floor rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtInstrumentFloorRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Floor rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Securities, Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Antidilutive Securities, Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Warrants to purchase common stock, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Warrant or Right, Number of Securities Called by Warrants or Rights</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants to purchase common stock, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsOther_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets, Other</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsOther_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restricted stock awards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementEquityComponentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Components [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementEquityComponentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Components</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ScheduleOfGrossToNetSalesAdjustmentsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Schedule of Reconciliation of Gross Product Sales to Net Product Sales</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ScheduleOfGrossToNetSalesAdjustmentsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Gross To Net Sales Adjustments [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ScheduleOfGrossToNetSalesAdjustmentsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of gross to net sales adjustments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, Address Line One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Address Line One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AccruedEndOfTermCharge_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued end of term charge.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AccruedEndOfTermCharge_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued End Of Term Charge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AccruedEndOfTermCharge_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued end of term charge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DollarPrepaymentCharge36MonthsAfterEffectiveDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Prepayment charge assessed upon debt prepayment occurring 36 months after June 30, 2022 under second amendment.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DollarPrepaymentCharge36MonthsAfterEffectiveDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dollar prepayment charge 36 months after effective date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DollarPrepaymentCharge36MonthsAfterEffectiveDate_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Charge for prepayment occurring 36 months after effective date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employee-related Liabilities, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued compensation and benefits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Employee-related Liabilities, Current, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Awards granted (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cyd_CybersecurityRiskProcessForInformingBoardCommitteeOrSubcommitteeResponsibleForOversightTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cybersecurity Risk Process for Informing Board Committee or Subcommittee Responsible for Oversight [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInLessThanOneYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents information pertaining to debentures, bonds and other debt securities issued by US government sponsored entities (GSEs), for example, but not limited to, Federal Home Loan Mortgage Corporation (FHLMC or Freddie Mac), Federal National Mortgage Association (FNMA or Fannie Mae), and the Federal Home Loan Bank (FHLB). Excludes debt issued by the Government National Mortgage Association (GNMA or Ginnie Mae, due in less than one year.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInLessThanOneYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">U S Government Sponsored Enterprises Debt Securities Due In Less Than One Year [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInLessThanOneYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Government-sponsored enterprise securities (due in less than one year)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_JanssenBiotechIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents information pertaining to the Janssen Biotech Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_JanssenBiotechIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Janssen Biotech Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_JanssenBiotechIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Janssen Biotech</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property Plant And Equipment [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpenseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Research and Development Expense [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpenseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Research and development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Event Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualLifeAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Weighted Average Remaining Contractual Life (In years)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualLifeAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options Weighted Average Remaining Contractual Life [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualLifeAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weight Average Remaining Contractual Life (in years) - Options Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Maximum Borrowing Capacity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum borrowing capacity under term loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TotalInterestAndOtherIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Total interest and other income (expense)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TotalInterestAndOtherIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Total Interest And Other Income Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TotalInterestAndOtherIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Total interest and other income (expense).</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ScheduleOfActivityWithinLiabilityRelatedToSaleOfFutureRoyaltiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Activity Within Liability Related To Sale Of Future Royalties Table Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ScheduleOfActivityWithinLiabilityRelatedToSaleOfFutureRoyaltiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of activity within liability related to sale of future royalties.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ScheduleOfActivityWithinLiabilityRelatedToSaleOfFutureRoyaltiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Schedule of Activity Within Liability Related to Sale of Future Royalties</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CaliforniaOfficeSpaceLeaseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">California Office Space Lease</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CaliforniaOfficeSpaceLeaseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">California Office Space Lease [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CaliforniaOfficeSpaceLeaseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">California office space lease.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnamortizedDebtIssuanceExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unamortized Debt Issuance Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnamortizedDebtIssuanceExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unamortized debt discount and issuance costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityVoluntaryFilers_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Voluntary Filers</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityVoluntaryFilers_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Voluntary Filers</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandAndEighteenInducementAwardPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand and eighteen inducement award plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandAndEighteenInducementAwardPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand And Eighteen Inducement Award Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandAndEighteenInducementAwardPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2018 Inducement Award Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AmendmentFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amendment Flag</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AmendmentFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amendment Flag</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLossCarryforwardsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Loss Carryforwards [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLossCarryforwardsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating Loss Carryforwards [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_IncreaseDecreaseInOperatingLeaseLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase decrease in operating lease liabilities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_IncreaseDecreaseInOperatingLeaseLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Operating Lease Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_IncreaseDecreaseInOperatingLeaseLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationByShareBasedPaymentAwardOptionsMaximumExpirationTermForOptionsGrantedToOptioneesWithOwnershipOfMoreThan10PercentageOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the maximum expiration term of options granted to employees having more than 10 % outstanding common stock.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationByShareBasedPaymentAwardOptionsMaximumExpirationTermForOptionsGrantedToOptioneesWithOwnershipOfMoreThan10PercentageOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation By Share Based Payment Award Options Maximum Expiration Term For Options Granted To Optionees With Ownership Of More Than10 Percentage Of Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationByShareBasedPaymentAwardOptionsMaximumExpirationTermForOptionsGrantedToOptioneesWithOwnershipOfMoreThan10PercentageOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum expiration term of stock options granted to employees having more than 10 % outstanding common stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_IncreaseDecreaseInAccruedInterestReceivableNetAndOtherReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">The increase (decrease) during the reporting period in the amount due for interest payments related to marketable securities and in other amounts due to the reporting entity, which are not otherwise defined in the taxonomy.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_IncreaseDecreaseInAccruedInterestReceivableNetAndOtherReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Accrued Interest Receivable Net And Other Receivables</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_IncreaseDecreaseInAccruedInterestReceivableNetAndOtherReceivables_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Interest and other receivables</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Liability, Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Noncurrent operating lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyTwoPreFundedWarrantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">2022 pre-funded warrant.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyTwoPreFundedWarrantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Two Pre Funded Warrant [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyTwoPreFundedWarrantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2022 Pre-Funded Warrant</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DomesticCountryMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Domestic Tax Jurisdiction [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DomesticCountryMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Federal</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument, Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Paid in Capital, Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional paid-in capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Noncurrent marketable securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Public offering price per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale of Stock, Price Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Combined public offering price per share of pre-funded warrants and accompanying stock purchase warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeLeaseDescriptionTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Lease, Description [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeLeaseDescriptionTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lessee Lease Description [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Stock options exercised (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingCostsAndExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Cost of goods sold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingCostsAndExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Costs and Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingCostsAndExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Operating Costs and Expenses, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options exercisable at the end of the period (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Research and Development Expense [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research and development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_HerculesAndSiliconValleyBankMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Hercules and Silicon Valley Bank. member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_HerculesAndSiliconValleyBankMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hercules And Silicon Valley Bank [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_HerculesAndSiliconValleyBankMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hercules and Silicon Valley Bank [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityComponentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Component [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityComponentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Component</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_BorrowingAvailableStartDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First date to available to drawdown any amount under a tranche.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_BorrowingAvailableStartDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Borrowing Available Start Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_BorrowingAvailableStartDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Start date to borrow under a tranche for a debt instrument</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statistical Measurement [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statistical Measurement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFinStmtErrorCorrectionFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Financial Statement Error Correction [Flag]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Nonoperating Income (Expense)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Other Nonoperating Income (Expense), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other income (expense), net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expiration term of stock options from date of grant</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cyd_CybersecurityRiskMateriallyAffectedOrReasonablyLikelyToMateriallyAffectRegistrantTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FurnitureAndFixturesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Furniture and Fixtures [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FurnitureAndFixturesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Furniture and computer equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disaggregation of Revenue [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesAvailableForGrantRollForward_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Shares Available For Grant</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesAvailableForGrantRollForward_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Shares Available For Grant Roll Forward</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesAvailableForGrantRollForward_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Shares Available For Grant</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CommonStockAggregateOfferingPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the aggregate offering price for which the entity may elect to issue and sell shares of its common stock under the sales agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CommonStockAggregateOfferingPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Aggregate Offering Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CommonStockAggregateOfferingPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate offering price of common stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cyd_CybersecurityRiskManagementProcessesIntegratedFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cybersecurity Risk Management Processes Integrated [Flag]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Income (Loss), Including Portion Attributable to Noncontrolling Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentVariableInterestRateTypeExtensibleEnumeration_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Variable Interest Rate, Type [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Shares Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, shares issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Stock Options Exercised</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash received from exercise of stock options (in dollars)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscount_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Debt discount amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Unamortized Discount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscount_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less: unamortized debt discount and issuance costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscount_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt Instrument, Unamortized Discount, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseDiscountRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Discount Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseDiscountRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating Lease, Percentage of Discount Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PayablesAndAccrualsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payables and Accruals [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxCreditCarryforwardTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tax Credit Carryforward [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxCreditCarryforwardTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tax Credit Carryforward [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedRoyaltiesCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Royalties</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedRoyaltiesCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Carrying value of liabilities related to sale of future revenues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedRoyaltiesCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Carrying value of liability related to sale of future royalties at November 1, 2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedRoyaltiesCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Carrying value of liability related to sale of future royalties at December 31, 2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ConsolidationItemsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consolidation Items [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseAndOtherAssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid Expense and Other Assets, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseAndOtherAssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid and other current assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Maximum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Risk-free interest rate range, maximum (as a percent)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options cancelled/forfeited/expired (in dollars per share)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PharmakonLoanAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pharmakon Loan Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PharmakonLoanAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Pharmakon loan agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PharmakonLoanAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pharmakon Loan Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CashAndCashEquivalentsUnrealizedLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the gross unrealized losses for cash and cash equivalents.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CashAndCashEquivalentsUnrealizedLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash And Cash Equivalents Unrealized Losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CashAndCashEquivalentsUnrealizedLosses_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Gross Unrealized Losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PrepaidOnOrAfterThirdAnniversaryButPriorToFourthAnniversaryOfFundingDateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid On Or After Third Anniversary But Prior To Fourth Anniversary Of Funding Date [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PrepaidOnOrAfterThirdAnniversaryButPriorToFourthAnniversaryOfFundingDateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Prepaid on or after third anniversary but prior to fourth anniversary of funding date.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PrepaidOnOrAfterThirdAnniversaryButPriorToFourthAnniversaryOfFundingDateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid On Or After Third Anniversary But Prior To Fourth Anniversary Of Funding Date [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_NumberOfSeverancePlan_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">severance plans</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_NumberOfSeverancePlan_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number Of Severance Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_NumberOfSeverancePlan_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number of severance plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TypeOfArrangementAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangement and Arrangement Other than Collaborative [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TypeOfArrangementAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Collaborative Arrangement and Arrangement Other than Collaborative</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CollaborativeArrangementDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangement Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CollaborativeArrangementDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">LICENSE AGREEMENT</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Comprehensive Income (Loss), Net of Tax, Attributable to Parent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Comprehensive loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares, Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balances (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Balances (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, shares outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of Shares - Options Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfComponentsOfIncomeTaxExpenseBenefitTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfComponentsOfIncomeTaxExpenseBenefitTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of provision for(benefit from) income taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Par or Stated Value Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, par value (in dollars per share)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-Sale</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from maturities of marketable securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SalesRevenueNetMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue Benchmark [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LongTermDebtGross_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Aggregate value of term loan, including accrued interest payable and end of term charge.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LongTermDebtGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long Term Debt Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LongTermDebtGross_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MunicipalBondsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Municipal Bonds [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MunicipalBondsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Municipal securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AtMarketIssuanceSalesAgreementsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">At Market Issuance Sales Agreements.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AtMarketIssuanceSalesAgreementsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">At Market Issuance Sales Agreements [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AtMarketIssuanceSalesAgreementsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">At Market Issuance Sales Agreements [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Securities [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Antidilutive Securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cyd_CybersecurityRiskProcessForInformingManagementOrCommitteesResponsibleTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cybersecurity Risk Process for Informing Management or Committees Responsible [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOrSaleOfEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Issuance or Sale of Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOrSaleOfEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net proceeds from public offering after deducting underwriting discount and other offering expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOrSaleOfEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Proceeds from Issuance or Sale of Equity, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PercentageOfInterestOnPastDueOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Added percentage to current interest rate under debt instrument to past due amounts.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PercentageOfInterestOnPastDueOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Interest On Past Due Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PercentageOfInterestOnPastDueOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional percentage of interest on past due amounts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityInteractiveDataCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Interactive Data Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityInteractiveDataCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Interactive Data Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProductMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Product [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProductMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Product Revenue, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CommercialExpensesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Commercial Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CommercialExpensesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commercial Expenses Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CommercialExpensesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Commercial expenses.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FacilityCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Facility charge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FacilityCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Facility Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statistical Measurement [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statistical Measurement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfOfferingPeriodsInWhichEmployeeMayParticipateAtOneTime_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the number of offering periods in which an employee can participate at a time in the purchase plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfOfferingPeriodsInWhichEmployeeMayParticipateAtOneTime_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Maximum Number Of Offering Periods In Which Employee May Participate At One Time</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfOfferingPeriodsInWhichEmployeeMayParticipateAtOneTime_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of offering periods in which an employee can participate at a time</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CardinalHealthIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cardinal Health Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CardinalHealthIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cardinal Health Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CardinalHealthIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cardinal Health Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stockholders' Equity, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated Other Comprehensive Gain (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_NewJerseyOfficeSpaceLeaseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">New jersey office space lease.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_NewJerseyOfficeSpaceLeaseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">New Jersey Office Space Lease [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_NewJerseyOfficeSpaceLeaseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">New Jersey Office Space Lease</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentPaymentTerms_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Payment Terms</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentPaymentTerms_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Description of term loan payment terms</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets, Fair Value Disclosure</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Assets, Fair Value Disclosure, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_RevenuesBeforeAdjustmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenues Before Adjustments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_RevenuesBeforeAdjustmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revenues before adjustments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_RevenuesBeforeAdjustmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Revenues Before Adjustments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lease, Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseCost_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total lease costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, Maturity [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Undiscounted future non-cancellable lease payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRisksTypesNoConcentrationPercentageAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Concentration Risks, Types, No Concentration Percentage [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRisksTypesNoConcentrationPercentageAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Credit Risk</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommercialPaperMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commercial Paper [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommercialPaperMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commercial paper</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Shares available for grant</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balance at the end of the period (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Balance at the beginning of the period (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options and awards available for grant (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average estimated fair value of other than employee stock options granted (in dollars per share)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Weighted average grant date fair value (in dollars per share)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Period for recognition of compensation cost on weighted average basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_MarketCapMinimumToUseOptionTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Minimum market capitalization required for this option to be available to meet the minimum cash balance debt covenant.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_MarketCapMinimumToUseOptionTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Market cap minimum to use option two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_MarketCapMinimumToUseOptionTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Minimum market capitalization requirement for option</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_MaximumCommissionRate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the percentage of maximum commission rate, based on gross proceeds of sale price per share of common stock sold through sales agent under the sales agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_MaximumCommissionRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Maximum Commission Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_MaximumCommissionRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum commission rate (as a percent)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingencyNatureDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Loss Contingency, Nature [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsLiabilitiesNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsLiabilitiesNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total net deferred tax assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpensePolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Research and Development Expense, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpensePolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research and Development Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Prepaid Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidExpense_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Prepaid expenses and other assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Income Location, Balance [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Statement Location</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedBalanceShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owned, Balance, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedBalanceShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of shares owned</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Assets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Assets_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expected term range</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_NumberOfFinancialInstitutions_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number of financial institutions.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_NumberOfFinancialInstitutions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number Of Financial Institutions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_NumberOfFinancialInstitutions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of financial institutions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_StockPurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Stock purchase warrants.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_StockPurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Purchase Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_StockPurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock Purchase Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ValuationAllowanceAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation Allowance [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ValuationAllowanceAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Valuation allowance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Long-Term Debt Instruments [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Foreign</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income (Loss) from Continuing Operations before Income Taxes, Foreign</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_IssuanceOfCommonStockInConnectionWithWarrantExerciseValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Equity impact of the value of stock issued in connection with exercise of warrants during the period.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_IssuanceOfCommonStockInConnectionWithWarrantExerciseValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Issuance Of Common Stock In Connection With Warrant Exercise Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_IssuanceOfCommonStockInConnectionWithWarrantExerciseValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock in connection with exercise of warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInEquitySecuritiesFvNi_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Equity Securities, FV-NI</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInEquitySecuritiesFvNi_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Increase (decrease) in fair value of equity investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">New Accounting Pronouncements, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Recent Accounting Pronouncements</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressCityOrTown_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, City or Town</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressCityOrTown_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, City or Town</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">AOCI Attributable to Parent [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated Other Comprehensive Gain (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation, Other Adjustments, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AuditorLocation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Auditor Location</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AuditorLocation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Auditor Location</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateContinuingOperationsTaxRateReconciliationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation, Percent [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateContinuingOperationsTaxRateReconciliationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtInstrumentMinimumPrepaymentAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Minimum amount allowed to be prepaid under debt instrument.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtInstrumentMinimumPrepaymentAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Minimum Prepayment Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtInstrumentMinimumPrepaymentAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum amount of prepayment allowed under debt instrument</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfMaturitiesOfLongTermDebtTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Maturities of Long-Term Debt [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfMaturitiesOfLongTermDebtTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Future Minimum Payments Under Term Loan Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cyd_CybersecurityRiskMateriallyAffectedOrReasonablyLikelyToMateriallyAffectRegistrantFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Flag]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ConsultantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents information pertaining to consultants.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ConsultantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consultants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ConsultantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Consultants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DeferredTaxAssetsRevenueParticipation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets Revenue Participation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DeferredTaxAssetsRevenueParticipation_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Deferred tax assets revenue participation.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DeferredTaxAssetsRevenueParticipation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue Participation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyFourUnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Four Underwritten Public Offering [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyFourUnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty four underwritten public offering.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyFourUnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2024 Underwritten Public Offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareholdersEquityAndShareBasedPaymentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shareholders' Equity and Share-Based Payments [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareholdersEquityAndShareBasedPaymentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">STOCKHOLDERS' EQUITY</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Principle amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Face Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Closing stock price (in dollars per share)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total fair value of restricted stock that vested</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ExpiryDateOfTranche_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expiration date to borrow under a tranche for a debt instrument</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ExpiryDateOfTranche_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Expiry Date Of Tranche</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ExpiryDateOfTranche_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Last date to drawdown any amounts under a tranche.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cyd_CybersecurityRiskThirdPartyOversightAndIdentificationProcessesFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cybersecurity Risk Third Party Oversight and Identification Processes [Flag]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LossContingencyTriggeringEventEmployeeTerminationWithoutCauseFollowingChangeOfControlPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the number of months following a change in control when an employee is terminated without cause to be classified as a triggering event for severance payments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LossContingencyTriggeringEventEmployeeTerminationWithoutCauseFollowingChangeOfControlPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Loss Contingency Triggering Event Employee Termination Without Cause Following Change Of Control Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LossContingencyTriggeringEventEmployeeTerminationWithoutCauseFollowingChangeOfControlPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Period within which employee is terminated by entity without cause following a change of control</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseShareBasedCompensationCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-Based Payment Arrangement, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseShareBasedCompensationCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock-based compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cyd_CybersecurityRiskManagementPositionsOrCommitteesResponsibleReportToBoardFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cybersecurity Risk Management Positions or Committees Responsible Report to Board [Flag]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Shares of common stock authorized for issuance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuances of common stock under equity plans (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NontradeReceivablesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Nontrade Receivables, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NontradeReceivablesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest and other receivables</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NontradeReceivablesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Nontrade Receivables, Current, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingCodmIndividualTitleAndPositionOrGroupOrCommitteeNameExtensibleEnumeration_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting, CODM, Individual Title and Position or Group Name [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosures [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_SeverancePlanLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Severance plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_SeverancePlanLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Severance Plan [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_SeverancePlanLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Severance Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TermLoansMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Term Loans [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TermLoansMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Term loans.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TermLoansMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Term Loans [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityPublicFloat_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Public Float</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityPublicFloat_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Public Float</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_UpfrontPaymentReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Upfront payment received</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_UpfrontPaymentReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Upfront Payment Received</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_UpfrontPaymentReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Upfront payment received.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_MinimumPercentageOfNetProductRevenuesMaintenancePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Minimum percentage of net product revenues maintenance period.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_MinimumPercentageOfNetProductRevenuesMaintenancePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Minimum percentage of net product revenues maintenance period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_MinimumPercentageOfNetProductRevenuesMaintenancePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Minimum percentage of net product revenues maintenance period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Value, New Issues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock in connection with at market offering, net of issuance costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net deferred tax assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets, Net of Valuation Allowance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeLeaseDescriptionLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Lease, Description [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeLeaseDescriptionLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lessee Lease Description [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities, Current [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current liabilities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseContractualTermAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lease Contractual Term [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseContractualTermAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease Contractual Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IssuanceOfStockAndWarrantsForServicesOrClaims_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Issuance of Stock and Warrants for Services or Claims</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IssuanceOfStockAndWarrantsForServicesOrClaims_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock-based compensation for services by non-employees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IssuanceOfStockAndWarrantsForServicesOrClaims_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Stock-based compensation for services by non-employees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_USTreasuryNotesSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">US Treasury Notes Securities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_USTreasuryNotesSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">U.S. Treasury securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsReceivableMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounts Receivable [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsReceivableMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts Receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentType_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentType_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentType_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Document Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_Security12bTitle_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Title of 12(b) Security</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_Security12bTitle_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Title of 12(b) Security</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash and Cash Equivalents, at Carrying Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash and cash equivalents</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Cash and Cash Equivalents, at Carrying Value, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityBorrowingCapacityDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Borrowing Capacity, Description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityBorrowingCapacityDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expiration date to borrow under a tranche for a debt instrument, description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DirectorsPlan2006Member_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents information pertaining to the 2006 Directors Plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DirectorsPlan2006Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Directors Plan2006 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DirectorsPlan2006Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2006 Directors Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, Year Five</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2029</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseCostTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lease, Cost [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseCostTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Components of lease costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cyd_CybersecurityRiskManagementStrategyAndGovernanceLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cybersecurity Risk Management, Strategy, and Governance [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Stockholders' Equity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PercentageOfCommitmentAmountToFundLoan_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Commitment Amount To Fund Loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PercentageOfCommitmentAmountToFundLoan_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of commitment amount to fund loan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PercentageOfCommitmentAmountToFundLoan_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of commitment amount to fund loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalPeriodFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Fiscal Period Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalPeriodFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Fiscal Period Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period, Intrinsic Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total pretax intrinsic value of stock options exercised (in dollars)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Research and Development Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Research and Development Expense, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Excluding Current Maturities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Noncurrent debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Noncurrent portion of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options granted (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Stock options granted (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Stock options granted (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Asset Class [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Asset Class</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property and equipment, gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Property, Plant and Equipment, Gross, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Property, Plant and Equipment, Gross, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Property, Plant and Equipment, Gross, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConsolidationPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consolidation, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConsolidationPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Principles of Consolidation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardDurationOfPurchasePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the duration of the purchase period under the employee stock purchase plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardDurationOfPurchasePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Duration Of Purchase Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardDurationOfPurchasePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Duration of the purchase period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event Type [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Event Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationActivityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Activity [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationActivityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of aggregate stock option and award activity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeLeasesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Leases [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeLeasesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Leases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Share-Based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of assumptions used to estimate the fair value of stock options granted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyPreFundedWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">2020 Pre-funded warrants.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyPreFundedWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Pre Funded Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyPreFundedWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2020 Pre-Funded Warrant</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PercentageOfPrepaymentCharge_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of prepayment amount to be paid upon prepayment under debt instrument.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PercentageOfPrepaymentCharge_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Prepayment Charge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PercentageOfPrepaymentCharge_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepayment charge (as a percentage)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingSegmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Segments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingSegmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Operating Segments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_UnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Underwritten Public Offering [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_UnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Underwritten Public Offering [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_UnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Underwritten Public Offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LicenseFeesAndRoyaltiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">License Fees And Royalties Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LicenseFeesAndRoyaltiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">License fees and royalties.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LicenseFeesAndRoyaltiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">License Fees and Royalties</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Maturity, after Year Five</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Thereafter</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">12 Months or Greater - Estimated Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Warrant or Right, Exercise Price of Warrants or Rights</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants exercise price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Warrants to purchase common stock, exercise price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Instruments [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financial Instruments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossUnrealized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrealized Gain (Loss), Foreign Currency Transaction, before Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossUnrealized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain (loss) related to foreign currency translation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DeferredTaxAssetsOperatingLeaseLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Deferred tax assets operating lease liabilities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DeferredTaxAssetsOperatingLeaseLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets Operating Lease Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DeferredTaxAssetsOperatingLeaseLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CostMethodInvestmentsCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cost method investments cost basis.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CostMethodInvestmentsCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cost Method Investments Cost Basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CostMethodInvestmentsCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cost method investments cost basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Warrant or Right [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsidiarySaleOfStockAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale of Stock [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsidiarySaleOfStockAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sale of Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided by (Used in) Investing Activities [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash flows from investing activities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTypeCategorizationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTypeCategorizationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInDepositOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Deposit Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInDepositOtherAssets_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Deposit and other assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInDepositOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Deposit Assets, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CARESActImpactAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">CARES act impact.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CARESActImpactAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">C A R E S Act Impact [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_GovernmentSponsoredEnterpriseSecuritiesDueInOneToTwoYearsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debentures, bonds and other debt securities issued by US government sponsored entities (GSEs), for example, but not limited to, Federal Home Loan Mortgage Corporation (FHLMC or Freddie Mac), Federal National Mortgage Association (FNMA or Fannie Mae), and the Federal Home Loan Bank (FHLB). Excludes debt issued by the Government National Mortgage Association (GNMA or Ginnie Mae) due in 1 to 2 years.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_GovernmentSponsoredEnterpriseSecuritiesDueInOneToTwoYearsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Government Sponsored Enterprise Securities Due In One To Two Years [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_GovernmentSponsoredEnterpriseSecuritiesDueInOneToTwoYearsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Government-sponsored enterprise securities (due in one to two years)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue from Contract with Customer, Excluding Assessed Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Total revenues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenues:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_lbl" xlink:role="http://www.xbrl.org/2009/role/netLabel">Net product revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMinimumPercentageOfOwnershipRequiredForGrantingOptionsAtMinimum110PercentOfFairMarketValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the minimum percentage of ownership required for granting of options at a price not less than 110 percent of the fair market value of common stock.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMinimumPercentageOfOwnershipRequiredForGrantingOptionsAtMinimum110PercentOfFairMarketValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Minimum Percentage Of Ownership Required For Granting Options At Minimum110 Percent Of Fair Market Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMinimumPercentageOfOwnershipRequiredForGrantingOptionsAtMinimum110PercentOfFairMarketValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum percentage of ownership required for granting stock options at least 110% of fair market value of common stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Comprehensive Income [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">INCOME TAXES</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Decrease related to prior year tax positions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule reconciles the federal statutory tax rate to the effective income tax rate from continuing operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cyd_CybersecurityRiskManagementStrategyAndGovernanceAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cybersecurity Risk Management, Strategy, and Governance [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashFlowSupplementalDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Flow, Supplemental Disclosures [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashFlowSupplementalDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">CONSOLIDATED STATEMENTS OF CASH FLOWS DATA</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Selling, general and administrative</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Selling, General and Administrative Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Selling, General and Administrative Expense, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CreditFacilityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Credit Facility [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CreditFacilityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Credit Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Securities Available For Sale [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Stockholders' Equity [Roll Forward]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Increase (Decrease) in Stockholders' Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Depreciation, Depletion and Amortization, Nonproduction</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Depreciation and amortization</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Depreciation, Depletion and Amortization, Nonproduction, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number of warrants exercised during the period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class Of Warrant Or Right Number Of Securities Called By Warrants Or Rights Exercised</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants to purchase common stock exercised, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Accrued Liabilities, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Accounts Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Accounts Payable, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine2_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, Address Line Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine2_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Address Line Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions and Methodology [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Assumptions used to estimate fair value of awards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities and Equity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">LIABILITIES AND STOCKHOLDERS' EQUITY</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CollaborativeArrangementAfterTerminationCostSharingPercentageOfEntity_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the percentage of costs that the company must pay after the termination of the Collaboration Agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CollaborativeArrangementAfterTerminationCostSharingPercentageOfEntity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangement After Termination Cost Sharing Percentage Of Entity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CollaborativeArrangementAfterTerminationCostSharingPercentageOfEntity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of costs to be paid by Geron after termination of Collaboration Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentPeriodEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Period End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentPeriodEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Period End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided by (Used in) Financing Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net cash provided by financing activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateBasisForEffectiveRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Interest Rate, Basis for Effective Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateBasisForEffectiveRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Term loan interest rate description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_IcfrAuditorAttestationFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/label">ICFR Auditor Attestation Flag</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_IcfrAuditorAttestationFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ICFR Auditor Attestation Flag</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateContinuingOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateContinuingOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Effective tax rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LitigationSettlementAmountAwardedToOtherParty_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Litigation Settlement, Amount Awarded to Other Party</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LitigationSettlementAmountAwardedToOtherParty_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Litigation settlement, amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityNoteAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stockholders' Equity Note [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PublicOfferingOfCommonStockAndWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Public Offering of Common Stock and Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PublicOfferingOfCommonStockAndWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Public Offering Of Common Stock And Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PublicOfferingOfCommonStockAndWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Public Offering of Common Stock and Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Potential dilutive securities excluded from diluted earnings (loss) per share calculation (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Depreciation [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Depreciation [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_EffectiveIncomeTaxRateReconciliationNetOperatingLossNotBenefitted_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Effective income tax Rate reconciliation net operating loss not benefitted.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_EffectiveIncomeTaxRateReconciliationNetOperatingLossNotBenefitted_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation Net Operating Loss Not Benefitted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_EffectiveIncomeTaxRateReconciliationNetOperatingLossNotBenefitted_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net operating loss not benefitted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">APIC, Share-Based Payment Arrangement, Increase for Cost Recognition</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock-based compensation for equity-based awards to employees and directors</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">APIC, Share-Based Payment Arrangement, Increase for Cost Recognition, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Liabilities, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Accrued liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, after Year Five</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Thereafter</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingCodmProfitLossMeasureHowUsedDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting, CODM, Profit (Loss) Measure, How Used, Description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingCodmProfitLossMeasureHowUsedDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Segment reporting, CODM, profit (loss) measure, how used, description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Expense (Benefit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Provision for (benefit from) income taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tranche four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tranche Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Marketable securities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CollaborativeArrangementNumberOfStudies_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the number of agreed upon studies.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CollaborativeArrangementNumberOfStudies_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangement Number Of Studies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CollaborativeArrangementNumberOfStudies_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of agreed upon studies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComponentsOfDeferredTaxAssetsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Components of Deferred Tax Assets [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComponentsOfDeferredTaxAssetsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Significant components of deferred tax assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_TradingSymbol_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Trading Symbol</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_TradingSymbol_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Trading Symbol</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity, Attributable to Parent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balances</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Balances</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total stockholders' equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SummaryOfInvestmentHoldingsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary of Investment Holdings [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandAndEighteenEquityIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">2018 equity incentive plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandAndEighteenEquityIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand And Eighteen Equity Incentive Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandAndEighteenEquityIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2018 Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumDurationOfOfferingPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the maximum duration of the offering period under the employee stock purchase plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumDurationOfOfferingPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Maximum Duration Of Offering Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumDurationOfOfferingPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum duration of offering period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsGross_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total deferred tax assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Lived Tangible Asset [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-Lived Tangible Asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Common stock outstanding warrants to purchase</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Warrant or Right, Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants outstanding (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock-Based Compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StateAndLocalIncomeTaxExpenseBenefitContinuingOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/label">State and Local Income Tax Expense (Benefit), Continuing Operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StateAndLocalIncomeTaxExpenseBenefitContinuingOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">State and Local Income Tax Expense (Benefit), Continuing Operations, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StateAndLocalIncomeTaxExpenseBenefitContinuingOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">State</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DepositsAndOtherAssetsNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Carrying value of amounts transferred to third parties for security purposes that are expected to be returned or applied towards payment after one year or beyond the operating cycle, if longer; and amount of noncurrent assets classified as other.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DepositsAndOtherAssetsNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deposits And Other Assets Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DepositsAndOtherAssetsNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deposits and other assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VariableLeaseCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Variable Lease, Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VariableLeaseCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Variable lease costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Property Plant And Equipment [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cyd_CybersecurityRiskManagementStrategyAndGovernanceTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cybersecurity Risk Management, Strategy, and Governance [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_RoyaltyPharmaRevenueParticipationRightPurchaseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Royalty Pharma Revenue Participation Right Purchase Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_RoyaltyPharmaRevenueParticipationRightPurchaseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Royalty Pharma Revenue Participation Right Purchase Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_RoyaltyPharmaRevenueParticipationRightPurchaseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Royalty Pharma Revenue Participation Right Purchase Agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_RoyaltyPharmaRevenueParticipationRightPurchaseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liabilities Related to Sale of Future Royalties</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Compensation cost not yet recognized, net of estimated forfeitures (in dollars)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cyd_CybersecurityRiskManagementExpertiseOfManagementResponsibleTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cybersecurity Risk Management Expertise of Management Responsible [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of allocation of stock-based compensation expense related to share-based payment awards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ClinicalSupplyAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Clinical supply agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ClinicalSupplyAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Clinical Supply Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ClinicalSupplyAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Clinical Supply Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Gross Unrealized Losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeasesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Leases [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AtMarketIssuanceTwoThousandAndTwentyThreeSalesAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2023 Sales Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AtMarketIssuanceTwoThousandAndTwentyThreeSalesAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">At Market Issuance Two Thousand And Twenty Three Sales Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AtMarketIssuanceTwoThousandAndTwentyThreeSalesAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">At market issuance two thousand and twenty three sales agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UseOfEstimates_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Use of Estimates, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UseOfEstimates_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Use of Estimates</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Purchase warrants.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Purchase Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchase Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Additional Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional disclosures</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PercentageOfRemainingTermCommitmentsHeldUnderLoanAgreement_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of remaining term commitments held under loan agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PercentageOfRemainingTermCommitmentsHeldUnderLoanAgreement_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Remaining Term Commitments Held Under Loan Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PercentageOfRemainingTermCommitmentsHeldUnderLoanAgreement_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of remaining term commitments held under loan agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfLongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Issuance of Long-Term Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfLongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from debt financing, net of paid debt issuance costs and debt discounts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfLongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Proceeds from Issuance of Long-Term Debt, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PublicOfferingStockIssuedDuringPeriodValueNewIssue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock, pre-funded warrant and warrants to purchase common stock in public offering, net of issuance costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PublicOfferingStockIssuedDuringPeriodValueNewIssue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Public Offering Stock Issued During Period Value New Issue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PublicOfferingStockIssuedDuringPeriodValueNewIssue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Public offering stock issued during period value new issues.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskPercentage1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Concentration Risk, Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskPercentage1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Concentration risk, percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Minimum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expected volatility range, minimum (as a percent)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_SalesReturnsAndAllowanceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sales Returns And Allowance [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_SalesReturnsAndAllowanceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Sales returns and allowance.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_SalesReturnsAndAllowanceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Sales returns and allowances</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StatementScenarioAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Scenario [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StatementScenarioAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Scenario</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Dividend Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividend yield (as a percent)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_SecurityExchangeName_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Security Exchange Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_SecurityExchangeName_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Security Exchange Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtCovenantMinimumCashBalance_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt Covenant Minimum Cash Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtCovenantMinimumCashBalance_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Covenant Minimum Cash Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtCovenantMinimumCashBalance_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt covenant minimum cash balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RepurchaseAgreementCounterpartyNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Counterparty Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RepurchaseAgreementCounterpartyNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Counterparty Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLossCarryforwardsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Loss Carryforwards [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLossCarryforwardsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating Loss Carryforwards [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total operating expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Lived Tangible Asset [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-Lived Tangible Asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueIssuedForServices_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Value, Issued for Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueIssuedForServices_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock-based compensation related to issuance of common stock and options in exchange for services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesByNatureOfContingencyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Loss Contingency Nature [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_Non-CashInterestExpenseOnLiabilitiesForSalesOfFutureRoyalities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Non-cash Interest Expense on Liabilities for Sales of Future Royalities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_Non-CashInterestExpenseOnLiabilitiesForSalesOfFutureRoyalities_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Non-cash interest expense on liabilities for sales of future royalities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_Non-CashInterestExpenseOnLiabilitiesForSalesOfFutureRoyalities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-cash interest expense on liabilities for sales of future royalities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LossContingencyPeriodOfCurrentBaseSalaryToBePaidUnderSeverancePlanNonChangeOfControlTriggeringEvent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Period of base salary in connection with a non-change of control to be considered for severance payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LossContingencyPeriodOfCurrentBaseSalaryToBePaidUnderSeverancePlanNonChangeOfControlTriggeringEvent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Loss Contingency Period Of Current Base Salary To Be Paid Under Severance Plan Non Change of Control Triggering Event</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LossContingencyPeriodOfCurrentBaseSalaryToBePaidUnderSeverancePlanNonChangeOfControlTriggeringEvent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Loss contingency period of current base salary to be paid under severance plan non change of control triggering event.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less accumulated depreciation and amortization</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosures [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">FAIR VALUE MEASUREMENTS</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, Year Three</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average estimated fair value of employee stock options granted (in dollars per share)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Event</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Maximum [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Maximum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AccruedEndOfTermCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued end of term charges.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AccruedEndOfTermCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued End Of Term Charges</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AccruedEndOfTermCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Accrued end of term charge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SummaryOfInvestmentHoldingsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Holdings [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Compensation cost related to unvested stock awards not yet recognized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities and Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total liabilities and stockholders' equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Loss of extinguishment of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss) on Extinguishment of Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Gain (Loss) on Extinguishment of Debt, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Loss on extinguishment of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Right-of-Use Asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating Lease, Right-of-Use Asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Operating leases, right-of-use assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Cash Flow Information [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental operating and investing activities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Earnings Per Share, Diluted, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Diluted net loss per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseholdImprovementsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Leasehold Improvements [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseholdImprovementsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Leasehold improvements</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ReconciliationOfRevenueFromSegmentsToConsolidatedTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Reconciliation of Revenue from Segments to Consolidated [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ReconciliationOfRevenueFromSegmentsToConsolidatedTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Schedule of Reconciliation of Reported Revenues to Net (Loss) Income Under Significant Expense Principle</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Liabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Liabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ReconciliationOfUnrecognizedTaxBenefitsExcludingAmountsPertainingToExaminedTaxReturnsRollForward_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrecognized Tax Benefits [Roll Forward]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ReconciliationOfUnrecognizedTaxBenefitsExcludingAmountsPertainingToExaminedTaxReturnsRollForward_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unrecognized tax benefits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_SeverancePlanTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Severance plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_SeverancePlanTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Severance Plan [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_SeverancePlanTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Severance Plan [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CorporateNoteSecuritiesDueInLessThanOneYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">This category includes information about short-term debt securities that are issued by either a domestic or foreign corporate business entity with a date certain promise of repayment and a return to the holder for the time value of money (for example, variable or fixed interest), due in less than one year.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CorporateNoteSecuritiesDueInLessThanOneYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Corporate Note Securities Due In Less Than One Year [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CorporateNoteSecuritiesDueInLessThanOneYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Corporate notes (due in less than one year)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Hierarchy and NAV [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Hierarchy and NAV</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ChargebackAndDistributorServiceFeesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Chargeback And Distributor Service Fees [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ChargebackAndDistributorServiceFeesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Chargeback and distributor service fees.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ChargebackAndDistributorServiceFeesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Chargebacks and distributor service fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total current assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided by (Used in) Investing Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net cash provided by (used in) investing activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioForecastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Forecast [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioForecastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Scenario Forecast [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Shares, New Issues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock in connection with at market offering, net of issuance costs (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrecognizedTaxBenefits_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrecognized Tax Benefits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrecognizedTaxBenefits_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balance at the end of the period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrecognizedTaxBenefits_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Balance at the beginning of the period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized Investment Gains (Losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Realized investment gains (losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Realized Investment Gains (Losses), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Change in valuation allowance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Vesting period of stock options</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFilerCategory_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Filer Category</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFilerCategory_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Filer Category</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingRevenueReconcilingItemLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting, Revenue Reconciling Item [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashAndInvestmentsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Cash and Investments [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashAndInvestmentsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restricted cash:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrecognized Tax Benefits that Would Impact Effective Tax Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unrecognized tax benefits, if recognized would impact effective tax rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireMarketableSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments to Acquire Marketable Securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireMarketableSecurities_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Purchases of marketable securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PercentageOfAnnualNetSales_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of annual net sales</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PercentageOfAnnualNetSales_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of annual net sales.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AtMarketIssuanceTwoThousandAndTwentySalesAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">At market issuance two thousand and twenty sales agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AtMarketIssuanceTwoThousandAndTwentySalesAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">At Market Issuance Two Thousand And Twenty Sales Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AtMarketIssuanceTwoThousandAndTwentySalesAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2020 Sales Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CurrentFiscalYearEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Current Fiscal Year End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CurrentFiscalYearEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current Fiscal Year End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value on a Recurring Basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, Undiscounted Excess Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less: imputed interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Noncash Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock-based compensation for employees and directors</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Share-Based Payment Arrangement, Noncash Expense, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_McKessonFinancialCenterMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">McKesson Financial Center [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_McKessonFinancialCenterMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">McKesson Financial Center.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_McKessonFinancialCenterMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">McKesson Financial Center</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Description of maturity date terms for term loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Intrinsic Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balance at the end of the period (in dollars)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsToBeGrantedToPurchaseSharesUponAppointment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the number of options to be granted to purchase shares upon appointment to Board of Directors.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsToBeGrantedToPurchaseSharesUponAppointment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options To Be Granted To Purchase Shares Upon Appointment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsToBeGrantedToPurchaseSharesUponAppointment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options to be granted to purchase shares upon appointment (shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyTwoUnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Information by type of sale of the entity's stock. = 2022 Underwritten Public Offering [Member].</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyTwoUnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Two Underwritten Public Offering [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyTwoUnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2022 Underwritten Public Offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityRegistrantName_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Registrant Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityRegistrantName_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Registrant Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_FosterCityOfficeSpaceLeaseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Foster City office space lease.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_FosterCityOfficeSpaceLeaseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Foster City Office Space Lease [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_FosterCityOfficeSpaceLeaseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Foster City Office Space Lease</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTotalLabel">Total - Gross Unrealized Losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_InterestOnlyPeriodPaymentTermDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest only period payment term description.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_InterestOnlyPeriodPaymentTermDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Only Period Payment Term Description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_InterestOnlyPeriodPaymentTermDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest only period payment term description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ScenarioTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Scenario Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ScenarioTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Scenario two .</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ScenarioTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Scenario Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfReportableSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of Reportable Segments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfReportableSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of reportable segment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Maturity Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Term loan maturity date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityEmergingGrowthCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Emerging Growth Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityEmergingGrowthCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Emerging Growth Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyPurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty purchase warrants.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyPurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Purchase Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyPurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2020 Purchase Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MoneyMarketFundsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Money Market Funds [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MoneyMarketFundsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Money market funds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Weighted Average Number of Shares Outstanding, Basic, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Number of Shares Outstanding, Basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Shares used in computing basic net loss per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LossContingencyTriggeringEventPeriodFollowingChangeOfControlDuringWhichNoComparableEmploymentIsOfferedByEntity_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the period following change of control within which an employee is not offered comparable employment (new or continuing) by the entity or its successor or acquired and to be considered as triggering event for severance payments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LossContingencyTriggeringEventPeriodFollowingChangeOfControlDuringWhichNoComparableEmploymentIsOfferedByEntity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Loss Contingency Triggering Event Period Following Change Of Control During Which No Comparable Employment Is Offered By Entity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LossContingencyTriggeringEventPeriodFollowingChangeOfControlDuringWhichNoComparableEmploymentIsOfferedByEntity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Period within which no comparable employment is offered by the entity following a change of control</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseOptionToTerminate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Option to Terminate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseOptionToTerminate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease term, option to terminate lease</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InsuranceClaimsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Insurance Claims [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InsuranceClaimsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Insurance Claims</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilitiesPaymentsDueAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, Fiscal Year Maturity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilitiesPaymentsDueAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating Lease Liabilities, Payments Due</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_HerculesLoanAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hercules Loan Agreement Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_HerculesLoanAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Hercules loan agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_HerculesLoanAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hercules Loan Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Maximum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expected volatility range, maximum (as a percent)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares Authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, shares authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Payable, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentUsefulLife_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment, Useful Life</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentUsefulLife_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Estimated useful lives of assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RoyaltyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Royalty [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RoyaltyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Royalties</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskByTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Concentration Risk Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash and Cash Equivalents [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Included in cash and cash equivalents:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel1Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 1 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel1Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Level 1</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumAmountOfAnnualSalaryThatCanBeWithheldPerYear_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum amount of annual salary that can be withheld to purchase shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumAmountOfAnnualSalaryThatCanBeWithheldPerYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Maximum Amount Of Annual Salary That Can Be Withheld Per Year</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumAmountOfAnnualSalaryThatCanBeWithheldPerYear_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Share based compensation arrangement by share based payment award maximum amount of annual salary that can be withheld per year.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options fully vested and expected to vest at the end of the period (in dollars per share)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentsIncorporatedByReferenceTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Documents Incorporated by Reference [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentsIncorporatedByReferenceTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Documents Incorporated by Reference</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options granted (in dollars per share)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialInstrumentAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Instrument [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialInstrumentAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financial Instrument</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtCovenantMinCashUponRegulatoryMilestone_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Minimum cash covenant required upon achievement of certain regulatory milestones.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtCovenantMinCashUponRegulatoryMilestone_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Covenant Min Cash Upon Regulatory Milestone</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtCovenantMinCashUponRegulatoryMilestone_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt covenant minimum cash balance upon regulatory milestone achievement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Balance at the end of the period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerSharePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerSharePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Loss Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AccruedManufacturingActivitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Carrying value as of the balance sheet of obligations incurred through the date and payable for manufacturing related costs. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AccruedManufacturingActivitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Manufacturing Activities Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AccruedManufacturingActivitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Manufacturing activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Issuance Costs and Debt Discounts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">General and Administrative Expense [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">General and administrative</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_EmployerTaxReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Carrying amount as of the balance sheet date of employer taxes paid to tax authorities representing refunds based on calculated eligible credits. Also called employer tax refund receivable.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_EmployerTaxReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employer Tax Receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_EmployerTaxReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Employee retention credit, CARES Act</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DeferredTaxLiabilitiesOperatingLeasesRightOfUseAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Deferred tax liabilities operating leases right of use assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DeferredTaxLiabilitiesOperatingLeasesRightOfUseAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Liabilities Operating Leases Right Of Use Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DeferredTaxLiabilitiesOperatingLeasesRightOfUseAssets_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Operating leases, right-of-use assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_GovernmentRebatesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Government Rebates [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_GovernmentRebatesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Government rebates.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_GovernmentRebatesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Government rebates</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt, Current, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpensePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Expense, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpensePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheSixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tranche Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheSixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tranche six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangement and Arrangement Other than Collaborative [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Collaborative Arrangements And Noncollaborative Arrangement Transactions [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_OptionOneMinCashDebtCovenantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Option one min cash debt covenant.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_OptionOneMinCashDebtCovenantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Option one min cash debt covenant [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuances of common stock under equity plans</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cyd_CybersecurityRiskRoleOfManagementTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cybersecurity Risk Role of Management [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_EmployeesAboveTheVicePresidentLevelMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Employees Above The Vice President Level</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_EmployeesAboveTheVicePresidentLevelMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employees Above The Vice President Level [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_EmployeesAboveTheVicePresidentLevelMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Employees above the vice president level.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_IncentiveAwardPlan2011Member_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents information pertaining to the 2011 Incentive Award Plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_IncentiveAwardPlan2011Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Award Plan2011 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_IncentiveAwardPlan2011Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2011 Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_RestrictedCashAndCashEquivalentsGrossUnrealizedLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Restricted cash and cash equivalents gross unrealized losses.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_RestrictedCashAndCashEquivalentsGrossUnrealizedLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Cash And Cash Equivalents Gross Unrealized Losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_RestrictedCashAndCashEquivalentsGrossUnrealizedLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gross Unrealized Losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Estimated Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt Securities, Available-for-Sale, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountingPoliciesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounting Policies [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationDepletionAndAmortizationPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Depreciation, Depletion, and Amortization [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationDepletionAndAmortizationPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Depreciation and Amortization</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Increase related to current year tax positions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity, Attributable to Parent [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stockholders' equity:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tranche Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tranche five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryRawMaterialsAndSupplies_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Inventory, Raw Materials and Supplies, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryRawMaterialsAndSupplies_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Inventory, Raw Materials and Supplies, Gross, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryRawMaterialsAndSupplies_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Raw materials</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxCreditCarryforwardLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tax Credit Carryforward [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxCreditCarryforwardLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tax Credit Carryforward [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsRestrictedCashAndCashEquivalentsPolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsRestrictedCashAndCashEquivalentsPolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restricted Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PerformanceBasedStockOptionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Performance based stock options.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PerformanceBasedStockOptionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Performance Based Stock Options [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PerformanceBasedStockOptionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Performance-Based Stock Options</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statement [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Segment Information</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ASDSpecialtyHealthcareLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">ASD Specialty Healthcare LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ASDSpecialtyHealthcareLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ASD Specialty Healthcare LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ASDSpecialtyHealthcareLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ASD Specialty Healthcare LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of property and equipment, stated at cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_HerculesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Hercules.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_HerculesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hercules [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options fully vested and expected to vest at the end of the period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted Average Exercise Price Per Share - Options Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Shares Authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, shares authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PrepaidOnOrAfterFourthAnniversaryOfFundingDateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid On Or After Fourth Anniversary Of Funding Date [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PrepaidOnOrAfterFourthAnniversaryOfFundingDateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Prepaid on or after fourth anniversary of funding date.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PrepaidOnOrAfterFourthAnniversaryOfFundingDateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid On Or After Fourth Anniversary Of Funding Date [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_OperatingLossCarryforwardsSubjectToExpiration_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net operating loss carryforwards, expire beginning 2024 through 2037</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_OperatingLossCarryforwardsSubjectToExpiration_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Operating loss carryforwards subject to expiration.</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue from Contract with Customer, Including Assessed Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Revenue interest payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFileNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity File Number</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net increase in cash, cash equivalents and restricted cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedCapitalizedInterestCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accumulated Capitalized Interest Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedCapitalizedInterestCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Less: amount representing interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedCapitalizedInterestCosts_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less: amount representing interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue from Contract with Customer [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-Based Compensation Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock-based compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">State income tax, net of federal benefit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AtMarketIssuanceTwoThousandAndEighteenSalesAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">At market issuance, 2018 sales agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AtMarketIssuanceTwoThousandAndEighteenSalesAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">At Market Issuance Two Thousand And Eighteen Sales Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_AtMarketIssuanceTwoThousandAndEighteenSalesAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2018 Sales Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Inventory Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseContractualTermDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lease Contractual Term [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseContractualTermDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease Contractual Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfFinancialPositionAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Financial Position [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Expense, Operating and Nonoperating</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Interest expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Interest Expense, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Income (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Loss from operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Loss from operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Maturity, Year One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesIssuedPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Public offering price of common stock per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesIssuedPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares Issued, Price Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesIssuedPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Combined public offering price per share of common stock and accompanying stock purchase warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedPaymentAwardEmployeeStockPurchasePlanValuationAssumptionsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Share-Based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedPaymentAwardEmployeeStockPurchasePlanValuationAssumptionsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of assumptions used to estimate the fair value of employee stock purchases under the purchase plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityShellCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Shell Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityShellCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Shell Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedProfessionalFeesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Professional Fees, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedProfessionalFeesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Professional legal and accounting fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateEffectivePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Effective interest rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateEffectivePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Interest Rate, Effective Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment, before Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment, before Tax, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net unrealized loss on marketable securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityTaxIdentificationNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Tax Identification Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityTaxIdentificationNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Tax Identification Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ASSETS</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueOfFinancialInstrumentsPolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value of Financial Instruments, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueOfFinancialInstrumentsPolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value of Financial Instruments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCurrentReportingStatus_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Current Reporting Status</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCurrentReportingStatus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Current Reporting Status</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Cash and Cash Equivalents, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restricted cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Amortized Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options exercisable at the end of the period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">PROPERTY AND EQUIPMENT</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Events [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">INVENTORY</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Inventory Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PrepaidPriorToThirdAnniversaryOfFundingDateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid Prior To Third Anniversary Of Funding Date [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PrepaidPriorToThirdAnniversaryOfFundingDateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Prepaid prior to third anniversary of funding date.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PrepaidPriorToThirdAnniversaryOfFundingDateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid Prior To Third Anniversary Of Funding Date [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue from Contract with Customer [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue Recognition</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_NoncurrentLiabilityRelatedToSaleOfFutureRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Noncurrent liability related to sale of future royalties</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_NoncurrentLiabilityRelatedToSaleOfFutureRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Noncurrent Liability Related to Sale of Future Royalties</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_NoncurrentLiabilityRelatedToSaleOfFutureRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Noncurrent liability related to sale of future royalties.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalYearFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Fiscal Year Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalYearFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Fiscal Year Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CashAndCashEquivalentsUnrealizedGains_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the gross unrealized gains for cash and cash equivalents.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CashAndCashEquivalentsUnrealizedGains_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash And Cash Equivalents Unrealized Gains</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CashAndCashEquivalentsUnrealizedGains_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gross Unrealized Gains</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CertificatesOfDepositMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Certificates of Deposit [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CertificatesOfDepositMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Certificate of deposit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Value, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, $0.001 par value; 3,000,000 shares authorized; no shares issued and outstanding at December 31, 2024 and 2023</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Stock options cancelled/forfeited/expired (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures and Expirations in Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures and Expirations in Period, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfLongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Repayments of Long-Term Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfLongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Repayments of Long-Term Debt, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfLongTermDebt_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Repayment of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfUnrecognizedTaxBenefitsRollForwardTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfUnrecognizedTaxBenefitsRollForwardTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of reconciliation of the beginning and ending amounts of unrecognized tax benefits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Cash, cash equivalents and restricted cash at the end of the period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Cash, cash equivalents and restricted cash at the beginning of the period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CostOfSalesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cost of Goods and Service [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CostOfSalesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cost of Goods Sold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxCreditCarryforwardAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tax Credit Carryforward, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxCreditCarryforwardAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tax credit carryforwards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CityAreaCode_lbl" xlink:role="http://www.xbrl.org/2003/role/label">City Area Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CityAreaCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">City Area Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfCashFlowSupplementalDisclosuresTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Cash Flow, Supplemental Disclosures [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfCashFlowSupplementalDisclosuresTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental schedule of non-cash operating and investing activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeReclassificationAdjustmentsNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other comprehensive income (loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeReclassificationAdjustmentsNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">OCI, Debt Securities, Available-for-Sale, Gain (Loss), before Adjustment, after Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeReclassificationAdjustmentsNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">OCI, Debt Securities, Available-for-Sale, Gain (Loss), before Adjustment, after Tax, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtInstrumentUnamortizedEndOfTermCharge_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt instrument unamortized end of term charge.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtInstrumentUnamortizedEndOfTermCharge_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Unamortized End Of Term Charge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtInstrumentUnamortizedEndOfTermCharge_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less: unamortized end of term charge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total current liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_RestrictedCashAndCashEquivalentsUnrealizedGains_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Restricted cash and cash equivalents unrealized gains.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_RestrictedCashAndCashEquivalentsUnrealizedGains_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Cash And Cash Equivalents Unrealized Gains</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_RestrictedCashAndCashEquivalentsUnrealizedGains_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gross Unrealized Gains</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardAggregateSharesIssuedUnderPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the aggregate number of share instruments issued under a share-based compensation plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardAggregateSharesIssuedUnderPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Aggregate Shares Issued Under Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardAggregateSharesIssuedUnderPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate shares issued under plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total inventory</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Inventory, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Inventory</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Securities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_SinaDrugMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sina Drug [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_SinaDrugMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Sina Drug.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_SinaDrugMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sina Drug</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryFinishedGoods_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Inventory, Finished Goods, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryFinishedGoods_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Finished goods</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tax at statutory rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyStockPurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two Thousand Twenty Stock Purchase Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyStockPurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Stock Purchase Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyStockPurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2020 Stock Purchase Warrant</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Organization, Consolidation and Presentation of Financial Statements [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_LocalPhoneNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Local Phone Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_LocalPhoneNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Local Phone Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LossContingencyTriggeringEventPeriodFollowingChangeOfControlWithinWhichEmployeeResignsDueToMaterialChangeInTermsOfEmployment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the period within which employee resigns following a change of control due to material change in terms of employment and to be considered as triggering event for severance payments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LossContingencyTriggeringEventPeriodFollowingChangeOfControlWithinWhichEmployeeResignsDueToMaterialChangeInTermsOfEmployment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Loss Contingency Triggering Event Period Following Change Of Control Within Which Employee Resigns Due To Material Change In Terms Of Employment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LossContingencyTriggeringEventPeriodFollowingChangeOfControlWithinWhichEmployeeResignsDueToMaterialChangeInTermsOfEmployment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Period within which employee resigns following a change of control due to material change in terms of employment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Shares Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, shares outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Preferred Stock, Shares Outstanding, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Preferred Stock, Shares Outstanding, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Antidilutive Securities Excluded from Computation of Earnings Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less Than 12 Months - Gross Unrealized Losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tranche two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tranche Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxAuthorityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Jurisdiction [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxAuthorityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Tax Authority</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromWarrantExercises_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Warrant Exercises</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromWarrantExercises_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from exercise of warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfIncomeBeforeIncomeTaxDomesticAndForeignTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of components of Income/(loss) before income taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfIncomeBeforeIncomeTaxDomesticAndForeignTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationCostOfAcquiredEntityEquityInterestsIssuedAndIssuableFairValueMethod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Combination, Consideration Transferred, Equity Interests Issued and Issuable Fair Value Method</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationCostOfAcquiredEntityEquityInterestsIssuedAndIssuableFairValueMethod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Business Combination Cost Of Acquired Entity Equity Interests Issued And Issuable Fair Value Method</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Amortized Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Amortized Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Deferred Tax Assets and Liabilities [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of significant components of the entity's deferred tax assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOtherIncreasesDecreasesInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Other Increases (Decreases) in Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOtherIncreasesDecreasesInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, increase in option reserves (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOtherIncreasesDecreasesInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Common stock, increase in shares reserved for future issuance (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Liability, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Operating lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tranche C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tranche C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tranche C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Foreign currency translation adjustment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxAuthorityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Jurisdiction [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxAuthorityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Tax Authority</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Stated interest rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Interest Rate, Stated Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum interest rate (as a percentage)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtInstrumentFaceAmountExpired_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument face amount expired</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtInstrumentFaceAmountExpired_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Face Amount Expired</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtInstrumentFaceAmountExpired_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt instrument face amount expired.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retained Earnings [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated Deficit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfFinancingCostsAndDiscounts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amortization of Debt Issuance Costs and Discounts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfFinancingCostsAndDiscounts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amortization of debt issuance costs/debt discount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfFinancingCostsAndDiscounts_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Amortization of Debt Issuance Costs and Discounts, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpenseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Selling, General and Administrative Expense [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpenseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Selling, general and administrative</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Purchases of property and equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments to Acquire Property, Plant, and Equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Payments to Acquire Property, Plant, and Equipment, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentTransitionReport_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Transition Report</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentTransitionReport_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Transition Report</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Purchase Price of Common Stock, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Percentage applied to common stock market value in calculating purchase price under purchase plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, Year Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumPercentageOfAnnualSalaryThatCanBeWithheld_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the maximum percentage of annual salary that an employee can choose to have withheld to purchase common stock under the purchase plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumPercentageOfAnnualSalaryThatCanBeWithheld_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Maximum Percentage Of Annual Salary That Can Be Withheld</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumPercentageOfAnnualSalaryThatCanBeWithheld_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum percentage of annual salary that can be withheld</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Security, Excluded EPS Calculation [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tranche three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TrancheThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tranche Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_OptionThreeMinCashDebtCovenantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Option three min cash debt covenant.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_OptionThreeMinCashDebtCovenantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Option three min cash debt covenant [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options exercised (in dollars per share)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less: unamortized debt discount and issuance costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AuditorFirmId_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Auditor Firm ID</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AuditorFirmId_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Auditor Firm ID</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Minimum [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Minimum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock-Based Compensation Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Maturity, Year Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableAndAccruedLiabilitiesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounts Payable and Accrued Liabilities Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableAndAccruedLiabilitiesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ACCRUED LIABILITIES</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options fully vested and expected to vest at the end of the period (in dollars)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_USTreasurySecuritiesDueInLessThanOneYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">US Treasury Securities Due In less than one Year Member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_USTreasurySecuritiesDueInLessThanOneYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">U S Treasury Securities Due In Less Than One Year [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_USTreasurySecuritiesDueInLessThanOneYearMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">U.S. Treasury securities (due in less than one year)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Right-of-Use Asset, Periodic Reduction</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amortization of right-of-use assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Paid-in Capital [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional Paid-In Capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityWellKnownSeasonedIssuer_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Well-known Seasoned Issuer</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityWellKnownSeasonedIssuer_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Well-known Seasoned Issuer</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Marketable securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyThreePreFundedWarrantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2023 Pre-funded Warrant</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyThreePreFundedWarrantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Three Pre Funded Warrant Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyThreePreFundedWarrantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty three pre funded warrant.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Income Location, Balance [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Statement Location</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyThreeUnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">2023 Public Offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyThreeUnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">2023 Underwritten Public Offering.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyThreeUnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Three Underwritten Public Offering [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyThreeUnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2023 Underwritten Public Offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, Year One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ChemistryManufacturingAndControlExpensesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Chemistry Manufacturing And Control Expenses Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ChemistryManufacturingAndControlExpensesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Chemistry, manufacturing, and control expenses.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ChemistryManufacturingAndControlExpensesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Chemistry, Manufacturing, and Control Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInOneToTwoYearsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents information pertaining to debentures, bonds and other debt securities issued by US government sponsored entities (GSEs), for example, but not limited to, Federal Home Loan Mortgage Corporation (FHLMC or Freddie Mac), Federal National Mortgage Association (FNMA or Fannie Mae), and the Federal Home Loan Bank (FHLB). Excludes debt issued by the Government National Mortgage Association (GNMA or Ginnie Mae), due in one to two years.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInOneToTwoYearsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">U S Government Sponsored Enterprises Debt Securities Due In One To Two Years [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInOneToTwoYearsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Government-sponsored enterprise securities (due in one to two years)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_EmployeeRetentionCreditAmountOutstandingReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Employee Retention Credit, Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_EmployeeRetentionCreditAmountOutstandingReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employee Retention Credit Amount Outstanding Receivables</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_EmployeeRetentionCreditAmountOutstandingReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Employee retention credit amount outstanding receivables.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfInventoryCurrentTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Inventory, Current [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfInventoryCurrentTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Schedule of Inventory</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_FormerCollaborativeArrangementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Former collaborative arrangement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_FormerCollaborativeArrangementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Former Collaborative Arrangement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_FormerCollaborativeArrangementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Former Collaboration Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ReclassificationBetweenPrepaidAndOtherCurrentAssetsAndDepositsAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Reclassification between prepaid and other current assets and deposits and other assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ReclassificationBetweenPrepaidAndOtherCurrentAssetsAndDepositsAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Reclassification Between Prepaid And Other Current Assets And Deposits And Other Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ReclassificationBetweenPrepaidAndOtherCurrentAssetsAndDepositsAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reclassification between prepaid and other current assets and deposits and other assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Common Stock, Shares Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Common Stock, Shares Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disaggregation of Revenue [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Less Than 12 Months - Estimated Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedGoodsAndNonemployeeServicesTransactionBySupplierAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplier [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedGoodsAndNonemployeeServicesTransactionBySupplierAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplier</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioUnspecifiedDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Scenario [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioUnspecifiedDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Scenario</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_TitleOfIndividualWithRelationshipToEntityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Title and Position [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingExpenseInformationUsedByCodmDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting, Expense Information Used by CODM, Description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingExpenseInformationUsedByCodmDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Segment reporting, expense information used by CODM, description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income (Loss) from Continuing Operations before Income Taxes, Domestic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Domestic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Value, Issued</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Employee Related Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued compensation and benefits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Employee Related Liabilities, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments for Royalties</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Royalty payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PrepaymentPremiumOnPercentageOfTermLoan_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepayment Premium on Percentage of Term Loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PrepaymentPremiumOnPercentageOfTermLoan_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">The prepayment premium on percentage of term loan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PrepaymentPremiumOnPercentageOfTermLoan_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepayment premium on percentage of term loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income, Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ProceedsFromPublicOfferingIssuanceOfCommonStockAndWarrants_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from public offering issuance of common stock and warrants.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ProceedsFromPublicOfferingIssuanceOfCommonStockAndWarrants_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds From Public Offering Issuance Of Common Stock And Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ProceedsFromPublicOfferingIssuanceOfCommonStockAndWarrants_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from issuance of common stock and warrants in public offering, net of paid issuance costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash and Cash Equivalents, Fair Value Disclosure</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Estimated Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CollaborativeArrangementCostSharingPercentageOfCounterparty_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents the percentage of costs that Janssen must pay during certain phases of the agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CollaborativeArrangementCostSharingPercentageOfCounterparty_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangement Cost Sharing Percentage Of Counterparty</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CollaborativeArrangementCostSharingPercentageOfCounterparty_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of costs to be paid by Janssen</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMinimumExercisePriceOfOptionsGrantedToEmployeesWithMoreThan10PercentageOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Share based compensation arrangement by share based payment award minimum exercise price of options granted to employees with more than 10 percentage of common stock.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMinimumExercisePriceOfOptionsGrantedToEmployeesWithMoreThan10PercentageOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Minimum Exercise Price Of Options Granted To Employees With More Than10 Percentage Of Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMinimumExercisePriceOfOptionsGrantedToEmployeesWithMoreThan10PercentageOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum exercise price as a percentage of fair market value for employees having more than 10 % outstanding common stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtInstrumentEndOfTermChargePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of outstanding loan amount payable upon maturity.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtInstrumentEndOfTermChargePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument End Of Term Charge Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_DebtInstrumentEndOfTermChargePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">End of term charge for loan, percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Maturity, Year Three</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating Lease, Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Operating Lease, Liability, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LiabilityRelatedToSaleOfFutureRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liability Related to Sale of Future Royalties</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LiabilityRelatedToSaleOfFutureRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Liability related to sale of future royalties.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LiabilityRelatedToSaleOfFutureRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liability related to sale of future royalties</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByMeasurementFrequencyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Frequency [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByMeasurementFrequencyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Measurement Frequency</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAccruedLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Accrued Liabilities [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAccruedLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of accrued liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsOperatingLossCarryforwards_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets, Operating Loss Carryforwards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsOperatingLossCarryforwards_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net operating loss carryforwards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsOperatingLossCarryforwards_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Deferred Tax Assets, Operating Loss Carryforwards, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitments and contingencies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PublicOfferingStockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Public offering stock issued during period shares new issues.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PublicOfferingStockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Public Offering Stock Issued During Period Shares New Issues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_PublicOfferingStockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock, pre-funded warrant and warrants to purchase common stock in public offering, net of issuance costs (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_EffectOfUnrealizedLossesAndExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Amount of increase (decrease) from effect of unrealized losses and exchange rate changes on cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage; held in foreign currencies; including, but not limited to, disposal group and discontinued operations. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_EffectOfUnrealizedLossesAndExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effect Of Unrealized Losses And Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_EffectOfUnrealizedLossesAndExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net effect of unrealized gains and exchange rates on cash, cash equivalents and restricted cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">12 Months or Greater - Gross Unrealized Losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_FairValueMeasurementsInterTransfersBetweenLevels_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair value measurements inter transfers between levels</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_FairValueMeasurementsInterTransfersBetweenLevels_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurements Inter Transfers Between Levels</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_FairValueMeasurementsInterTransfersBetweenLevels_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value measurements inter transfers between levels.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Weighted Average Number of Shares Outstanding, Diluted, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Number of Shares Outstanding, Diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Shares used in computing diluted net loss per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Research and Development Expense (Excluding Acquired in Process Cost)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research and development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsReceivableNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounts Receivable, after Allowance for Credit Loss, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsReceivableNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Accounts Receivable, after Allowance for Credit Loss, Current, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsReceivableNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts receivable, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseRenewalTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Renewal Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseRenewalTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease term, option to extend additional period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options fully vested and expected to vest at the end of the period (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total lease payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInInventories_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Inventories</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInInventories_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Inventories, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInInventories_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Inventory</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LossContingencyPeriodOfCurrentBaseSalaryToBePaidUnderSeverancePlan_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Loss contingency period of current base salary to be paid under severance plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LossContingencyPeriodOfCurrentBaseSalaryToBePaidUnderSeverancePlan_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Loss Contingency Period Of Current Base Salary To Be Paid Under Severance Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_LossContingencyPeriodOfCurrentBaseSalaryToBePaidUnderSeverancePlan_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Period of base salary to be considered for severance payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="cyd_CybersecurityRiskManagementThirdPartyEngagedFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cybersecurity Risk Management Third Party Engaged [Flag]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_SubsequentDirectorOptionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Represents information pertaining to the stock options to be granted by the entity subsequent to the grant upon first appointment to the Board of Directors.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_SubsequentDirectorOptionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Director Option [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_SubsequentDirectorOptionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Director Option</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyTwoStockPurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">2022 Stock Purchase Warrants.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyTwoStockPurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Two Stock Purchase Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_TwoThousandTwentyTwoStockPurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2022 Stock Purchase Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskBenchmarkDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Concentration Risk Benchmark [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WarrantsAndRightsOutstandingMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants expiration date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WarrantsAndRightsOutstandingMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Warrants and Rights Outstanding, Maturity Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskCustomer_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Concentration Risk, Customer</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskCustomer_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Concentration risk, customer</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CorporateNoteSecuritiesDueInOneToTwoYearsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">This category includes information about short-term debt securities that are issued by either a domestic or foreign corporate business entity with a date certain promise of repayment and a return to the holder for the time value of money (for example, variable or fixed interest), due in one to two years.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CorporateNoteSecuritiesDueInOneToTwoYearsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Corporate Note Securities Due In One To Two Years [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_CorporateNoteSecuritiesDueInOneToTwoYearsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Corporate notes (due in one to two years)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignIncomeTaxExpenseBenefitContinuingOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Foreign</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignIncomeTaxExpenseBenefitContinuingOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Foreign Income Tax Expense (Benefit), Continuing Operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignIncomeTaxExpenseBenefitContinuingOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Foreign Income Tax Expense (Benefit), Continuing Operations, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntitySmallBusiness_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Small Business</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntitySmallBusiness_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Small Business</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_NewJerseyLeaseAndFosterCityLeaseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">New Jersey lease and Foster city lease member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_NewJerseyLeaseAndFosterCityLeaseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">New Jersey Lease And Foster City Lease [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="gern_NewJerseyLeaseAndFosterCityLeaseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">New Jersey Lease And Foster City Lease</link:label>
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  <xsd:element id="gern_EmployeeRetentionCreditAmountOutstandingReceivables" name="EmployeeRetentionCreditAmountOutstandingReceivables" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_StockPurchaseWarrantsMember" name="StockPurchaseWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_TrancheBMember" name="TrancheBMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_SeverancePlanTable" name="SeverancePlanTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_AtTheMarketOfferingMember" name="AtTheMarketOfferingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_JanssenBiotechIncMember" name="JanssenBiotechIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_LicenseAgreementDisclosureAbstract" name="LicenseAgreementDisclosureAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_HerculesMember" name="HerculesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_LossContingencyTriggeringEventPeriodFollowingChangeOfControlWithinWhichEmployeeResignsDueToMaterialChangeInTermsOfEmployment" name="LossContingencyTriggeringEventPeriodFollowingChangeOfControlWithinWhichEmployeeResignsDueToMaterialChangeInTermsOfEmployment" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_FairValueMeasurementsInterTransfersBetweenLevels" name="FairValueMeasurementsInterTransfersBetweenLevels" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_AtMarketIssuanceSalesAgreementsTable" name="AtMarketIssuanceSalesAgreementsTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_DebtCovenantMinimumCashBalance" name="DebtCovenantMinimumCashBalance" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_TwoThousandTwentyTwoStockPurchaseWarrantsMember" name="TwoThousandTwentyTwoStockPurchaseWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardAggregateSharesIssuedUnderPlan" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardAggregateSharesIssuedUnderPlan" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_CollaborativeArrangementNumberOfStudies" name="CollaborativeArrangementNumberOfStudies" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_ProceedsFromPublicOfferingIssuanceOfCommonStockAndWarrants" name="ProceedsFromPublicOfferingIssuanceOfCommonStockAndWarrants" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_DebtCovenantMinimumCashBalancePercentageOfLoanAmount" name="DebtCovenantMinimumCashBalancePercentageOfLoanAmount" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_USTreasurySecuritiesDueInLessThanOneYearMember" name="USTreasurySecuritiesDueInLessThanOneYearMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_PreFundedWarrantsMember" name="PreFundedWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_GovernmentSponsoredEnterpriseSecuritiesDueInLessThanOneYearMember" name="GovernmentSponsoredEnterpriseSecuritiesDueInLessThanOneYearMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsExercised" name="ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsExercised" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="gern_TwoThousandTwentyStockPurchaseWarrantsMember" name="TwoThousandTwentyStockPurchaseWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_GovernmentSponsoredEnterpriseSecuritiesDueInOneToTwoYearsMember" name="GovernmentSponsoredEnterpriseSecuritiesDueInOneToTwoYearsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_DebtInstrumentFaceAmountExpired" name="DebtInstrumentFaceAmountExpired" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_DebtInstrumentMinimumPrepaymentAmount" name="DebtInstrumentMinimumPrepaymentAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_ShareBasedCompensationForfeituresAndExpirationsInPeriodNet" name="ShareBasedCompensationForfeituresAndExpirationsInPeriodNet" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_NewJerseyOfficeSpaceLeaseMember" name="NewJerseyOfficeSpaceLeaseMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_TwoThousandTwentyFourPreFundedWarrantMember" name="TwoThousandTwentyFourPreFundedWarrantMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_TrancheTwoMember" name="TrancheTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_DebtInstrumentEndOfTermChargePercentage" name="DebtInstrumentEndOfTermChargePercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_PercentageOfCommitmentAmountToFundLoan" name="PercentageOfCommitmentAmountToFundLoan" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="gern_DebtCovenantMinCashUponRegulatoryMilestone" name="DebtCovenantMinCashUponRegulatoryMilestone" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_TrancheFourMember" name="TrancheFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_DeferredTaxAssetsFederalAndStateCredits" name="DeferredTaxAssetsFederalAndStateCredits" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_LossContingencyPeriodOfCurrentBaseSalaryToBePaidUnderSeverancePlanNonChangeOfControlTriggeringEvent" name="LossContingencyPeriodOfCurrentBaseSalaryToBePaidUnderSeverancePlanNonChangeOfControlTriggeringEvent" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_ReclassificationBetweenPrepaidAndOtherCurrentAssetsAndDepositsAndOtherAssets" name="ReclassificationBetweenPrepaidAndOtherCurrentAssetsAndDepositsAndOtherAssets" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_McKessonFinancialCenterMember" name="McKessonFinancialCenterMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_CommercialExpensesMember" name="CommercialExpensesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_ShareBasedCompensationByShareBasedPaymentAwardOptionsMaximumExpirationTermForOptionsGrantedToOptioneesWithOwnershipOfMoreThan10PercentageOfCommonStock" name="ShareBasedCompensationByShareBasedPaymentAwardOptionsMaximumExpirationTermForOptionsGrantedToOptioneesWithOwnershipOfMoreThan10PercentageOfCommonStock" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_SinaDrugMember" name="SinaDrugMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfOfferingPeriodsInWhichEmployeeMayParticipateAtOneTime" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfOfferingPeriodsInWhichEmployeeMayParticipateAtOneTime" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_TwoThousandTwentyPreFundedWarrantsMember" name="TwoThousandTwentyPreFundedWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_CARESActImpactAbstract" name="CARESActImpactAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_OptionThreeMinCashDebtCovenantMember" name="OptionThreeMinCashDebtCovenantMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_IncreaseDecreaseInOperatingLeaseLiabilities" name="IncreaseDecreaseInOperatingLeaseLiabilities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_TrancheOneMember" name="TrancheOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInOneToTwoYearsMember" name="USGovernmentSponsoredEnterprisesDebtSecuritiesDueInOneToTwoYearsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_ShareOfCommonStockIssuedDuringPeriodSharesNewIssuesPublicOffering" name="ShareOfCommonStockIssuedDuringPeriodSharesNewIssuesPublicOffering" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_DepositsAndOtherAssetsNoncurrent" name="DepositsAndOtherAssetsNoncurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_NumberOfFinancialInstitutions" name="NumberOfFinancialInstitutions" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="gern_PercentageOfPrepaymentCharge" name="PercentageOfPrepaymentCharge" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_TermLoansMember" name="TermLoansMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_DollarPrepaymentCharge36MonthsAfterEffectiveDate" name="DollarPrepaymentCharge36MonthsAfterEffectiveDate" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_PrepaidOnOrAfterThirdAnniversaryButPriorToFourthAnniversaryOfFundingDateMember" name="PrepaidOnOrAfterThirdAnniversaryButPriorToFourthAnniversaryOfFundingDateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_PublicOfferingTable" name="PublicOfferingTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_PrepaidOnOrAfterFourthAnniversaryOfFundingDateMember" name="PrepaidOnOrAfterFourthAnniversaryOfFundingDateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_LossContingencyPeriodOfCurrentBaseSalaryToBePaidUnderSeverancePlan" name="LossContingencyPeriodOfCurrentBaseSalaryToBePaidUnderSeverancePlan" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardDurationOfPurchasePeriod" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardDurationOfPurchasePeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_InterestOnlyPeriodPaymentTermDescription" name="InterestOnlyPeriodPaymentTermDescription" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_OptionTwoMinCashDebtCovenantMember" name="OptionTwoMinCashDebtCovenantMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_PercentageOfAnnualNetSales" name="PercentageOfAnnualNetSales" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_DebtInstrumentUnamortizedEndOfTermCharge" name="DebtInstrumentUnamortizedEndOfTermCharge" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_NumberOfSeverancePlan" name="NumberOfSeverancePlan" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumPercentageOfAnnualSalaryThatCanBeWithheld" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumPercentageOfAnnualSalaryThatCanBeWithheld" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumDurationOfOfferingPeriod" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumDurationOfOfferingPeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_TwoThousandTwentyTwoPreFundedWarrantMember" name="TwoThousandTwentyTwoPreFundedWarrantMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_AccruedManufacturingActivitiesCurrent" name="AccruedManufacturingActivitiesCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_AtMarketIssuanceTwoThousandAndTwentyThreeSalesAgreementMember" name="AtMarketIssuanceTwoThousandAndTwentyThreeSalesAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_LicenseFeesAndRoyaltiesMember" name="LicenseFeesAndRoyaltiesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_RoyaltyPharmaRevenueParticipationRightPurchaseAgreementMember" name="RoyaltyPharmaRevenueParticipationRightPurchaseAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_CorporateNoteSecuritiesDueInLessThanOneYearMember" name="CorporateNoteSecuritiesDueInLessThanOneYearMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_EquityInvestmentReverseStockSplit" name="EquityInvestmentReverseStockSplit" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_LossContingencyTriggeringEventPeriodFollowingChangeOfControlDuringWhichNoComparableEmploymentIsOfferedByEntity" name="LossContingencyTriggeringEventPeriodFollowingChangeOfControlDuringWhichNoComparableEmploymentIsOfferedByEntity" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_DirectorsPlan2006Member" name="DirectorsPlan2006Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_PublicOfferingStockIssuedDuringPeriodSharesNewIssues" name="PublicOfferingStockIssuedDuringPeriodSharesNewIssues" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_PurchaseWarrantsMember" name="PurchaseWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_BiopharmaCreditPlcMember" name="BiopharmaCreditPlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_IssuanceOfCommonStockInConnectionWithWarrantExerciseValue" name="IssuanceOfCommonStockInConnectionWithWarrantExerciseValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_SalesReturnsAndAllowanceMember" name="SalesReturnsAndAllowanceMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_TwoThousandTwentyTwoPurchaseWarrantsMember" name="TwoThousandTwentyTwoPurchaseWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_CostMethodInvestmentOwnershipPercentage" name="CostMethodInvestmentOwnershipPercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="gern_DeferredTaxLiabilitiesOperatingLeasesRightOfUseAssets" name="DeferredTaxLiabilitiesOperatingLeasesRightOfUseAssets" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_NumberOfSharesSoldFromEquityInvestment" name="NumberOfSharesSoldFromEquityInvestment" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_ScheduleOfCommonStockReservedForFutureIssuanceTableTextBlock" name="ScheduleOfCommonStockReservedForFutureIssuanceTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_ChemistryManufacturingAndControlExpensesMember" name="ChemistryManufacturingAndControlExpensesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_PrepaymentPremiumOnPercentageOfTermLoan" name="PrepaymentPremiumOnPercentageOfTermLoan" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_ProceedsFromSaleOfFutureRoyalties" name="ProceedsFromSaleOfFutureRoyalties" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_UpfrontPaymentReceived" name="UpfrontPaymentReceived" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_TwoThousandAndEighteenEquityIncentivePlanMember" name="TwoThousandAndEighteenEquityIncentivePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_FormerCollaborativeArrangementMember" name="FormerCollaborativeArrangementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_TwoThousandAndEighteenInducementAwardPlanMember" name="TwoThousandAndEighteenInducementAwardPlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_TrancheFiveMember" name="TrancheFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_SeverancePlanLineItems" name="SeverancePlanLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_USGovernmentSponsoredEnterprisesDebtSecuritiesDueInLessThanOneYearMember" name="USGovernmentSponsoredEnterprisesDebtSecuritiesDueInLessThanOneYearMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_PublicOfferingStockIssuedDuringPeriodValueNewIssue" name="PublicOfferingStockIssuedDuringPeriodValueNewIssue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_AccruedClinicalResearchOrganizationsAndClinicalTrialCostsCurrent" name="AccruedClinicalResearchOrganizationsAndClinicalTrialCostsCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_IssuanceOfCommonStockInConnectionWithWarrantExerciseShares" name="IssuanceOfCommonStockInConnectionWithWarrantExerciseShares" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_MunicipalSecuritiesDueInLessThanOneYearMember" name="MunicipalSecuritiesDueInLessThanOneYearMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_NoncurrentLiabilityRelatedToSaleOfFutureRoyalties" name="NoncurrentLiabilityRelatedToSaleOfFutureRoyalties" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_PercentageOfInterestOnPastDueOutstanding" name="PercentageOfInterestOnPastDueOutstanding" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_DebtInstrumentFloorRate" name="DebtInstrumentFloorRate" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="gern_NewJerseyLeaseAndFosterCityLeaseMember" name="NewJerseyLeaseAndFosterCityLeaseMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_TotalGrossToNetAdjustmentsMember" name="TotalGrossToNetAdjustmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_OperatingLeaseRentAbatementPeriod" name="OperatingLeaseRentAbatementPeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_HerculesLoanAgreementMember" name="HerculesLoanAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_TrancheThreeMember" name="TrancheThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_CollaborativeArrangementCostSharingPercentageOfCounterparty" name="CollaborativeArrangementCostSharingPercentageOfCounterparty" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_EffectOfUnrealizedLossesAndExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations" name="EffectOfUnrealizedLossesAndExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsToBeGrantedToPurchaseSharesUponAppointment" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsToBeGrantedToPurchaseSharesUponAppointment" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="gern_DueToCounterParty" name="DueToCounterParty" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_LongTermDebtGross" name="LongTermDebtGross" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_DeferredTaxAssetsRevenueParticipation" name="DeferredTaxAssetsRevenueParticipation" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_DeferredTaxAssetsCapitalizedResearchAndDevelopment" name="DeferredTaxAssetsCapitalizedResearchAndDevelopment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_AtMarketIssuanceSalesAgreementsLineItems" name="AtMarketIssuanceSalesAgreementsLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMinimumExercisePriceOfOptionsGrantedToEmployeesWithMoreThan10PercentageOfCommonStock" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardMinimumExercisePriceOfOptionsGrantedToEmployeesWithMoreThan10PercentageOfCommonStock" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="gern_LossContingencyTriggeringEventEmployeeTerminationWithoutCauseFollowingChangeOfControlPeriod" name="LossContingencyTriggeringEventEmployeeTerminationWithoutCauseFollowingChangeOfControlPeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_MarketCapMinimumToUseOptionTwo" name="MarketCapMinimumToUseOptionTwo" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_TwoThousandTwentyThreeUnderwrittenPublicOfferingMember" name="TwoThousandTwentyThreeUnderwrittenPublicOfferingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_DeferredTaxAssetsOperatingLeaseLiabilities" name="DeferredTaxAssetsOperatingLeaseLiabilities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfConsecutivePurchasePeriodsInEachOfferingPeriod" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfConsecutivePurchasePeriodsInEachOfferingPeriod" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_PharmakonLoanAgreementMember" name="PharmakonLoanAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_SiliconValleyBankMember" name="SiliconValleyBankMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_EmployerTaxReceivable" name="EmployerTaxReceivable" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_IncreaseDecreaseInAccruedInterestReceivableNetAndOtherReceivables" name="IncreaseDecreaseInAccruedInterestReceivableNetAndOtherReceivables" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_CollaborativeArrangementAfterTerminationCostSharingPercentageOfEntity" name="CollaborativeArrangementAfterTerminationCostSharingPercentageOfEntity" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_PublicOfferingLineItems" name="PublicOfferingLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_AtMarketIssuanceTwoThousandAndTwentySalesAgreementMember" name="AtMarketIssuanceTwoThousandAndTwentySalesAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_TwoThousandTwentyTwoUnderwrittenPublicOfferingMember" name="TwoThousandTwentyTwoUnderwrittenPublicOfferingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_MunicipalSecuritiesDueInOneToTwoYearsMember" name="MunicipalSecuritiesDueInOneToTwoYearsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_ScenarioOneMember" name="ScenarioOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_RestrictedCashAndCashEquivalentsUnrealizedGains" name="RestrictedCashAndCashEquivalentsUnrealizedGains" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_ScenarioTwoMember" name="ScenarioTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_CommonStockAggregateOfferingPrice" name="CommonStockAggregateOfferingPrice" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualLifeAbstract" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualLifeAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_OptionOneMinCashDebtCovenantMember" name="OptionOneMinCashDebtCovenantMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_HerculesAndSiliconValleyBankMember" name="HerculesAndSiliconValleyBankMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_PublicOfferingOfCommonStockAndWarrantsMember" name="PublicOfferingOfCommonStockAndWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_CardinalHealthIncMember" name="CardinalHealthIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_RevenuesBeforeAdjustmentsMember" name="RevenuesBeforeAdjustmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_EffectiveIncomeTaxRateReconciliationNetOperatingLossNotBenefitted" name="EffectiveIncomeTaxRateReconciliationNetOperatingLossNotBenefitted" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_MaximumCommissionRate" name="MaximumCommissionRate" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_TrancheAMember" name="TrancheAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_TwoThousandTwentyPurchaseWarrantsMember" name="TwoThousandTwentyPurchaseWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_BorrowingAvailableStartDate" name="BorrowingAvailableStartDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_RestrictedCashAndCashEquivalentsGrossUnrealizedLosses" name="RestrictedCashAndCashEquivalentsGrossUnrealizedLosses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_UnderwrittenPublicOfferingMember" name="UnderwrittenPublicOfferingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_ExpiryDateOfTranche" name="ExpiryDateOfTranche" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_PrepaidPriorToThirdAnniversaryOfFundingDateMember" name="PrepaidPriorToThirdAnniversaryOfFundingDateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_CashAndCashEquivalentsUnrealizedLosses" name="CashAndCashEquivalentsUnrealizedLosses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_OperatingLeaseTermAdditionalPeriodExtension" name="OperatingLeaseTermAdditionalPeriodExtension" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardMinimumPercentageOfOwnershipRequiredForGrantingOptionsAtMinimum110PercentOfFairMarketValue" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardMinimumPercentageOfOwnershipRequiredForGrantingOptionsAtMinimum110PercentOfFairMarketValue" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="gern_PerformanceBasedStockOptionsMember" name="PerformanceBasedStockOptionsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_AtMarketIssuanceTwoThousandAndEighteenSalesAgreementMember" name="AtMarketIssuanceTwoThousandAndEighteenSalesAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_ScheduleOfActivityWithinLiabilityRelatedToSaleOfFutureRoyaltiesTableTextBlock" name="ScheduleOfActivityWithinLiabilityRelatedToSaleOfFutureRoyaltiesTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_IncreaseInAllowanceForDoubtfulAccounts" name="IncreaseInAllowanceForDoubtfulAccounts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_LiabilityRelatedToSaleOfFutureRoyalties" name="LiabilityRelatedToSaleOfFutureRoyalties" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_EmployeesAboveTheVicePresidentLevelMember" name="EmployeesAboveTheVicePresidentLevelMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_MenloParkOfficeSpaceLeaseMember" name="MenloParkOfficeSpaceLeaseMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_DebtCovenantMinCashUponLicensingTransaction" name="DebtCovenantMinCashUponLicensingTransaction" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_DebtCovenantPercentageOfProductRevenueAgainstForecast" name="DebtCovenantPercentageOfProductRevenueAgainstForecast" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_PercentageOfRemainingTermCommitmentsHeldUnderLoanAgreement" name="PercentageOfRemainingTermCommitmentsHeldUnderLoanAgreement" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="gern_ASDSpecialtyHealthcareLLCMember" name="ASDSpecialtyHealthcareLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_CostMethodInvestmentsCostBasis" name="CostMethodInvestmentsCostBasis" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsIntrinsicValueAbstract" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsIntrinsicValueAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_CashAndCashEquivalentsUnrealizedGains" name="CashAndCashEquivalentsUnrealizedGains" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_AccruedEndOfTermCharges" name="AccruedEndOfTermCharges" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_TrancheCMember" name="TrancheCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_TrancheSixMember" name="TrancheSixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsToBeGrantedToPurchaseShares" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsToBeGrantedToPurchaseShares" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="gern_FirstDirectorOptionMember" name="FirstDirectorOptionMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_ResearchAndClinicalExpensesMember" name="ResearchAndClinicalExpensesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_SubsequentDirectorOptionMember" name="SubsequentDirectorOptionMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_DirectorsMarketValueStockPurchasePlanMember" name="DirectorsMarketValueStockPurchasePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_FosterCityOfficeSpaceLeaseMember" name="FosterCityOfficeSpaceLeaseMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_MinimumPercentageOfNetProductRevenuesMaintenancePeriod" name="MinimumPercentageOfNetProductRevenuesMaintenancePeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="gern_CaliforniaOfficeSpaceLeaseMember" name="CaliforniaOfficeSpaceLeaseMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_AccruedEndOfTermCharge" name="AccruedEndOfTermCharge" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="gern_ChargebackAndDistributorServiceFeesMember" name="ChargebackAndDistributorServiceFeesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_PaymentOnRoyaltyAgreement" name="PaymentOnRoyaltyAgreement" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="gern_CorporateNoteSecuritiesDueInOneToTwoYearsMember" name="CorporateNoteSecuritiesDueInOneToTwoYearsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="gern_ScheduleOfGrossToNetSalesAdjustmentsTableTextBlock" name="ScheduleOfGrossToNetSalesAdjustmentsTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
</xsd:schema>
