<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2022 Workiva-->
<!--r:f3cecbd3-1833-4433-b854-055b0860fb3c,g:55333f8f-3d06-40dd-9f33-fa25b6931800-->
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:omcl="http://www.omnicell.com/20220630" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2020-01-21" attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://www.omnicell.com/20220630">
  <xs:import namespace="http://fasb.org/srt/2022" schemaLocation="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd"/>
  <xs:import namespace="http://fasb.org/us-gaap/2022" schemaLocation="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd"/>
  <xs:import namespace="http://www.w3.org/1999/xlink" schemaLocation="http://www.xbrl.org/2003/xlink-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/dtr/type/2020-01-21" schemaLocation="https://www.xbrl.org/dtr/type/2020-01-21/types.xsd"/>
  <xs:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/country/2022" schemaLocation="https://xbrl.sec.gov/country/2022/country-2022.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/dei/2022" schemaLocation="https://xbrl.sec.gov/dei/2022/dei-2022.xsd"/>
  <xs:annotation>
    <xs:appinfo>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="omcl-20220630_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="omcl-20220630_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="omcl-20220630_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="omcl-20220630_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:type="simple"/>
      <link:roleType id="Cover" roleURI="http://www.omnicell.com/role/Cover">
        <link:definition>0001001 - Document - Cover</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedBalanceSheetsUnaudited" roleURI="http://www.omnicell.com/role/CondensedConsolidatedBalanceSheetsUnaudited">
        <link:definition>1001002 - Statement - Condensed Consolidated Balance Sheets (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedBalanceSheetsUnauditedParenthetical" roleURI="http://www.omnicell.com/role/CondensedConsolidatedBalanceSheetsUnauditedParenthetical">
        <link:definition>1002003 - Statement - Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedStatementsofOperationsUnaudited" roleURI="http://www.omnicell.com/role/CondensedConsolidatedStatementsofOperationsUnaudited">
        <link:definition>1003004 - Statement - Condensed Consolidated Statements of Operations (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedStatementsofComprehensiveIncomeUnaudited" roleURI="http://www.omnicell.com/role/CondensedConsolidatedStatementsofComprehensiveIncomeUnaudited">
        <link:definition>1004005 - Statement - Condensed Consolidated Statements of Comprehensive Income (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedStatementsofStockholdersEquityUnaudited" roleURI="http://www.omnicell.com/role/CondensedConsolidatedStatementsofStockholdersEquityUnaudited">
        <link:definition>1005006 - Statement - Condensed Consolidated Statements of Stockholders' Equity (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedStatementsofCashFlowsUnaudited" roleURI="http://www.omnicell.com/role/CondensedConsolidatedStatementsofCashFlowsUnaudited">
        <link:definition>1006007 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="OrganizationandSummaryofSignificantAccountingPolicies" roleURI="http://www.omnicell.com/role/OrganizationandSummaryofSignificantAccountingPolicies">
        <link:definition>2101101 - Disclosure - Organization and Summary of Significant Accounting Policies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="OrganizationandSummaryofSignificantAccountingPoliciesPolicies" roleURI="http://www.omnicell.com/role/OrganizationandSummaryofSignificantAccountingPoliciesPolicies">
        <link:definition>2202201 - Disclosure - Organization and Summary of Significant Accounting Policies (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AccountingPoliciesTables" roleURI="http://www.omnicell.com/role/AccountingPoliciesTables">
        <link:definition>2303301 - Disclosure - Accounting Policies (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="OrganizationandSummaryofSignificantAccountingPoliciesNarrativeDetails" roleURI="http://www.omnicell.com/role/OrganizationandSummaryofSignificantAccountingPoliciesNarrativeDetails">
        <link:definition>2404401 - Disclosure - Organization and Summary of Significant Accounting Policies - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="OrganizationandSummaryofSignificantAccountingPoliciesScheduleofAdoptionImpactsfromASU202006Details" roleURI="http://www.omnicell.com/role/OrganizationandSummaryofSignificantAccountingPoliciesScheduleofAdoptionImpactsfromASU202006Details">
        <link:definition>2405402 - Disclosure - Organization and Summary of Significant Accounting Policies - Schedule of Adoption Impacts from ASU 2020-06 (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessCombinations" roleURI="http://www.omnicell.com/role/BusinessCombinations">
        <link:definition>2106102 - Disclosure - Business Combinations</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessCombinationsTables" roleURI="http://www.omnicell.com/role/BusinessCombinationsTables">
        <link:definition>2307302 - Disclosure - Business Combinations (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessCombinationsNarrativeDetails" roleURI="http://www.omnicell.com/role/BusinessCombinationsNarrativeDetails">
        <link:definition>2408403 - Disclosure - Business Combinations - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessCombinationsSummaryofPreliminaryPurchasePriceDetails" roleURI="http://www.omnicell.com/role/BusinessCombinationsSummaryofPreliminaryPurchasePriceDetails">
        <link:definition>2409404 - Disclosure - Business Combinations - Summary of Preliminary Purchase Price (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessCombinationsPreliminaryAllocationofthePurchasePricetotheAssetsAcquiredandtheLiabilitiesAssumedbytheCompanyDetails" roleURI="http://www.omnicell.com/role/BusinessCombinationsPreliminaryAllocationofthePurchasePricetotheAssetsAcquiredandtheLiabilitiesAssumedbytheCompanyDetails">
        <link:definition>2410405 - Disclosure - Business Combinations - Preliminary Allocation of the Purchase Price to the Assets Acquired and the Liabilities Assumed by the Company (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessCombinationsSummaryofIdentifiableIntangibleAssetsAcquiredDetails" roleURI="http://www.omnicell.com/role/BusinessCombinationsSummaryofIdentifiableIntangibleAssetsAcquiredDetails">
        <link:definition>2411406 - Disclosure - Business Combinations - Summary of Identifiable Intangible Assets Acquired (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessCombinationsProFormaFinancialInformationDetails" roleURI="http://www.omnicell.com/role/BusinessCombinationsProFormaFinancialInformationDetails">
        <link:definition>2412407 - Disclosure - Business Combinations - Pro Forma Financial Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessCombinationsandAssetAcquisitionsPolicies" roleURI="http://www.omnicell.com/role/BusinessCombinationsandAssetAcquisitionsPolicies">
        <link:definition>2213202 - Disclosure - Business Combinations and Asset Acquisitions (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Revenues" roleURI="http://www.omnicell.com/role/Revenues">
        <link:definition>2114103 - Disclosure - Revenues</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenuesTables" roleURI="http://www.omnicell.com/role/RevenuesTables">
        <link:definition>2315303 - Disclosure - Revenues (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenuesNarrativeDetails" roleURI="http://www.omnicell.com/role/RevenuesNarrativeDetails">
        <link:definition>2416408 - Disclosure - Revenues - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenuesDisaggregationofRevenuesbyRevenueTypeDetails" roleURI="http://www.omnicell.com/role/RevenuesDisaggregationofRevenuesbyRevenueTypeDetails">
        <link:definition>2417409 - Disclosure - Revenues - Disaggregation of Revenues by Revenue Type (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenuesDisaggregationofRevenuesbyGeographicLocationDetails" roleURI="http://www.omnicell.com/role/RevenuesDisaggregationofRevenuesbyGeographicLocationDetails">
        <link:definition>2418410 - Disclosure - Revenues - Disaggregation of Revenues by Geographic Location (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenuesContractAssetandLiabilitiesDetails" roleURI="http://www.omnicell.com/role/RevenuesContractAssetandLiabilitiesDetails">
        <link:definition>2419411 - Disclosure - Revenues - Contract Asset and Liabilities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="NetIncomePerShare" roleURI="http://www.omnicell.com/role/NetIncomePerShare">
        <link:definition>2120104 - Disclosure - Net Income Per Share</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="NetIncomePerShareTables" roleURI="http://www.omnicell.com/role/NetIncomePerShareTables">
        <link:definition>2321304 - Disclosure - Net Income Per Share (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="NetIncomePerShareDetails" roleURI="http://www.omnicell.com/role/NetIncomePerShareDetails">
        <link:definition>2422412 - Disclosure - Net Income Per Share (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CashandCashEquivalentsandFairValueofFinancialInstruments" roleURI="http://www.omnicell.com/role/CashandCashEquivalentsandFairValueofFinancialInstruments">
        <link:definition>2123105 - Disclosure - Cash and Cash Equivalents and Fair Value of Financial Instruments</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CashandCashEquivalentsandFairValueofFinancialInstrumentsDetails" roleURI="http://www.omnicell.com/role/CashandCashEquivalentsandFairValueofFinancialInstrumentsDetails">
        <link:definition>2424413 - Disclosure - Cash and Cash Equivalents and Fair Value of Financial Instruments (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BalanceSheetComponents" roleURI="http://www.omnicell.com/role/BalanceSheetComponents">
        <link:definition>2125106 - Disclosure - Balance Sheet Components</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BalanceSheetComponentsTables" roleURI="http://www.omnicell.com/role/BalanceSheetComponentsTables">
        <link:definition>2326305 - Disclosure - Balance Sheet Components (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BalanceSheetComponentsBalanceSheetComponentsDetails" roleURI="http://www.omnicell.com/role/BalanceSheetComponentsBalanceSheetComponentsDetails">
        <link:definition>2427414 - Disclosure - Balance Sheet Components - Balance Sheet Components (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BalanceSheetComponentsScheduleofAccumulatedOtherComprehensiveIncomeLossDetails" roleURI="http://www.omnicell.com/role/BalanceSheetComponentsScheduleofAccumulatedOtherComprehensiveIncomeLossDetails">
        <link:definition>2428415 - Disclosure - Balance Sheet Components - Schedule of Accumulated Other Comprehensive Income (Loss) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="PropertyandEquipment" roleURI="http://www.omnicell.com/role/PropertyandEquipment">
        <link:definition>2129107 - Disclosure - Property and Equipment</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="PropertyandEquipmentTables" roleURI="http://www.omnicell.com/role/PropertyandEquipmentTables">
        <link:definition>2330306 - Disclosure - Property and Equipment (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="PropertyandEquipmentPropertyPlantandEquipmentBalancesDetails" roleURI="http://www.omnicell.com/role/PropertyandEquipmentPropertyPlantandEquipmentBalancesDetails">
        <link:definition>2431416 - Disclosure - Property and Equipment - Property, Plant and Equipment Balances (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="PropertyandEquipmentNarrativeDetails" roleURI="http://www.omnicell.com/role/PropertyandEquipmentNarrativeDetails">
        <link:definition>2432417 - Disclosure - Property and Equipment - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="PropertyandEquipmentSummaryofGeographicInformationforPropertyandEquipmentNetDetails" roleURI="http://www.omnicell.com/role/PropertyandEquipmentSummaryofGeographicInformationforPropertyandEquipmentNetDetails">
        <link:definition>2433418 - Disclosure - Property and Equipment - Summary of Geographic Information for Property and Equipment, Net (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssets" roleURI="http://www.omnicell.com/role/GoodwillandIntangibleAssets">
        <link:definition>2134108 - Disclosure - Goodwill and Intangible Assets</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssetsTables" roleURI="http://www.omnicell.com/role/GoodwillandIntangibleAssetsTables">
        <link:definition>2335307 - Disclosure - Goodwill and Intangible Assets (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssetsChangesinCarryingAmountofGoodwillDetails" roleURI="http://www.omnicell.com/role/GoodwillandIntangibleAssetsChangesinCarryingAmountofGoodwillDetails">
        <link:definition>2436419 - Disclosure - Goodwill and Intangible Assets - Changes in Carrying Amount of Goodwill (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssetsCarryingAmountsandUsefulLivesofIntangibleAssetsDetails" roleURI="http://www.omnicell.com/role/GoodwillandIntangibleAssetsCarryingAmountsandUsefulLivesofIntangibleAssetsDetails">
        <link:definition>2437420 - Disclosure - Goodwill and Intangible Assets - Carrying Amounts and Useful Lives of Intangible Assets (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssetsNarrativeDetails" roleURI="http://www.omnicell.com/role/GoodwillandIntangibleAssetsNarrativeDetails">
        <link:definition>2438421 - Disclosure - Goodwill and Intangible Assets - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssetsFutureAmortizationExpenseforIntangibleAssetsDetails" roleURI="http://www.omnicell.com/role/GoodwillandIntangibleAssetsFutureAmortizationExpenseforIntangibleAssetsDetails">
        <link:definition>2439422 - Disclosure - Goodwill and Intangible Assets - Future Amortization Expense for Intangible Assets (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DebtandCreditAgreement" roleURI="http://www.omnicell.com/role/DebtandCreditAgreement">
        <link:definition>2140109 - Disclosure - Debt and Credit Agreement</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DebtandCreditAgreementDetails" roleURI="http://www.omnicell.com/role/DebtandCreditAgreementDetails">
        <link:definition>2441423 - Disclosure - Debt and Credit Agreement (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConvertibleSeniorNotes" roleURI="http://www.omnicell.com/role/ConvertibleSeniorNotes">
        <link:definition>2142110 - Disclosure - Convertible Senior Notes</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConvertibleSeniorNotesTables" roleURI="http://www.omnicell.com/role/ConvertibleSeniorNotesTables">
        <link:definition>2343308 - Disclosure - Convertible Senior Notes (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConvertibleSeniorNotesNarrativeDetails" roleURI="http://www.omnicell.com/role/ConvertibleSeniorNotesNarrativeDetails">
        <link:definition>2444424 - Disclosure - Convertible Senior Notes - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConvertibleSeniorNotesConvertibleDebtBalancesDetails" roleURI="http://www.omnicell.com/role/ConvertibleSeniorNotesConvertibleDebtBalancesDetails">
        <link:definition>2445425 - Disclosure - Convertible Senior Notes - Convertible Debt Balances (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConvertibleSeniorNotesSummaryofComponentsofInterestExpenseDetails" roleURI="http://www.omnicell.com/role/ConvertibleSeniorNotesSummaryofComponentsofInterestExpenseDetails">
        <link:definition>2446426 - Disclosure - Convertible Senior Notes - Summary of Components of Interest Expense (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LessorLeases" roleURI="http://www.omnicell.com/role/LessorLeases">
        <link:definition>2147111 - Disclosure - Lessor Leases</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LessorLeasesTables" roleURI="http://www.omnicell.com/role/LessorLeasesTables">
        <link:definition>2348309 - Disclosure - Lessor Leases (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LessorLeasesNarrativeDetails" roleURI="http://www.omnicell.com/role/LessorLeasesNarrativeDetails">
        <link:definition>2449427 - Disclosure - Lessor Leases - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LessorLeasesIncomeRecognizedfromSalesTypeLeasesDetails" roleURI="http://www.omnicell.com/role/LessorLeasesIncomeRecognizedfromSalesTypeLeasesDetails">
        <link:definition>2450428 - Disclosure - Lessor Leases - Income Recognized from Sales-Type Leases (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LessorLeasesComponentsofSalesTypeLeaseReceivablesDetails" roleURI="http://www.omnicell.com/role/LessorLeasesComponentsofSalesTypeLeaseReceivablesDetails">
        <link:definition>2451429 - Disclosure - Lessor Leases - Components of Sales-Type Lease Receivables (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LessorLeasesMaturityScheduleofFutureMinimumLeasePaymentsunderSalesTypeLeasesDetails" roleURI="http://www.omnicell.com/role/LessorLeasesMaturityScheduleofFutureMinimumLeasePaymentsunderSalesTypeLeasesDetails">
        <link:definition>2452430 - Disclosure - Lessor Leases - Maturity Schedule of Future Minimum Lease Payments under Sales-Type Leases (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LessorLeasesMaturityScheduleofFutureMinimumLeasePaymentsunderSalesTypeLeasesDetails_1" roleURI="http://www.omnicell.com/role/LessorLeasesMaturityScheduleofFutureMinimumLeasePaymentsunderSalesTypeLeasesDetails_1">
        <link:definition>2452430 - Disclosure - Lessor Leases - Maturity Schedule of Future Minimum Lease Payments under Sales-Type Leases (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LessorLeasesIncomeRecognizedfromOperatingLeasesDetails" roleURI="http://www.omnicell.com/role/LessorLeasesIncomeRecognizedfromOperatingLeasesDetails">
        <link:definition>2453431 - Disclosure - Lessor Leases - Income Recognized from Operating Leases (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LesseeLeases" roleURI="http://www.omnicell.com/role/LesseeLeases">
        <link:definition>2154112 - Disclosure - Lessee Leases</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LesseeLeasesTables" roleURI="http://www.omnicell.com/role/LesseeLeasesTables">
        <link:definition>2355310 - Disclosure - Lessee Leases (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LesseeLeasesNarrativeDetails" roleURI="http://www.omnicell.com/role/LesseeLeasesNarrativeDetails">
        <link:definition>2456432 - Disclosure - Lessee Leases - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LesseeLeasesMaturityScheduleofFutureMinimumLeasePaymentsunderOperatingLeasesandtheReconciliationtotheOperatingLeaseLiabilitiesDetails" roleURI="http://www.omnicell.com/role/LesseeLeasesMaturityScheduleofFutureMinimumLeasePaymentsunderOperatingLeasesandtheReconciliationtotheOperatingLeaseLiabilitiesDetails">
        <link:definition>2457433 - Disclosure - Lessee Leases - Maturity Schedule of Future Minimum Lease Payments under Operating Leases and&#160;the Reconciliation to the Operating Lease Liabilities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LesseeLeasesMaturityScheduleofFutureMinimumLeasePaymentsunderOperatingLeasesandtheReconciliationtotheOperatingLeaseLiabilitiesDetails_1" roleURI="http://www.omnicell.com/role/LesseeLeasesMaturityScheduleofFutureMinimumLeasePaymentsunderOperatingLeasesandtheReconciliationtotheOperatingLeaseLiabilitiesDetails_1">
        <link:definition>2457433 - Disclosure - Lessee Leases - Maturity Schedule of Future Minimum Lease Payments under Operating Leases and&#160;the Reconciliation to the Operating Lease Liabilities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LesseeLeasesSupplementalCashFlowInformationRelatedtoOperatingLeasesDetails" roleURI="http://www.omnicell.com/role/LesseeLeasesSupplementalCashFlowInformationRelatedtoOperatingLeasesDetails">
        <link:definition>2458434 - Disclosure - Lessee Leases - Supplemental Cash Flow Information Related to Operating Leases (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LesseeLeasesWeightedAverageRemainingLeaseTermandWeightedAverageDiscountRateDetails" roleURI="http://www.omnicell.com/role/LesseeLeasesWeightedAverageRemainingLeaseTermandWeightedAverageDiscountRateDetails">
        <link:definition>2459435 - Disclosure - Lessee Leases - Weighted-Average Remaining Lease Term and Weighted-Average Discount Rate (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CommitmentsandContingencies" roleURI="http://www.omnicell.com/role/CommitmentsandContingencies">
        <link:definition>2160113 - Disclosure - Commitments and Contingencies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CommitmentsandContingenciesDetails" roleURI="http://www.omnicell.com/role/CommitmentsandContingenciesDetails">
        <link:definition>2461436 - Disclosure - Commitments and Contingencies (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxes" roleURI="http://www.omnicell.com/role/IncomeTaxes">
        <link:definition>2162114 - Disclosure - Income Taxes</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesDetails" roleURI="http://www.omnicell.com/role/IncomeTaxesDetails">
        <link:definition>2463437 - Disclosure - Income Taxes (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitsandShareBasedCompensation" roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensation">
        <link:definition>2164115 - Disclosure - Employee Benefits and Share-Based Compensation</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitsandShareBasedCompensationTables" roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationTables">
        <link:definition>2365311 - Disclosure - Employee Benefits and Share-Based Compensation (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitsandShareBasedCompensationSharedbasedCompensationExpenseDetails" roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationSharedbasedCompensationExpenseDetails">
        <link:definition>2466438 - Disclosure - Employee Benefits and Share-Based Compensation - Shared-based Compensation Expense (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitsandShareBasedCompensationAssumptionsUsedtoValueESPPSharesDetails" roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationAssumptionsUsedtoValueESPPSharesDetails">
        <link:definition>2467439 - Disclosure - Employee Benefits and Share-Based Compensation - Assumptions Used to Value ESPP Shares (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitsandShareBasedCompensationNarrativeDetails" roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationNarrativeDetails">
        <link:definition>2468440 - Disclosure - Employee Benefits and Share-Based Compensation - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitsandShareBasedCompensationAssumptionsUsedtoValueStockOptionsGrantedDetails" roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationAssumptionsUsedtoValueStockOptionsGrantedDetails">
        <link:definition>2469441 - Disclosure - Employee Benefits and Share-Based Compensation - Assumptions Used to Value Stock Options Granted (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitsandShareBasedCompensationSummaryofShareOptionActivityDetails" roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationSummaryofShareOptionActivityDetails">
        <link:definition>2470442 - Disclosure - Employee Benefits and Share-Based Compensation - Summary of Share Option Activity (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitsandShareBasedCompensationSummaryofRestrictedStockUnitActivityDetails" roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationSummaryofRestrictedStockUnitActivityDetails">
        <link:definition>2471443 - Disclosure - Employee Benefits and Share-Based Compensation - Summary of Restricted Stock Unit Activity (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitsandShareBasedCompensationSummaryofRestrictedStockAwardActivityDetails" roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationSummaryofRestrictedStockAwardActivityDetails">
        <link:definition>2472444 - Disclosure - Employee Benefits and Share-Based Compensation - Summary of Restricted Stock Award Activity (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitsandShareBasedCompensationSummaryofPerformanceBasedRestrictedStockActivityDetails" roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationSummaryofPerformanceBasedRestrictedStockActivityDetails">
        <link:definition>2473445 - Disclosure - Employee Benefits and Share-Based Compensation - Summary of Performance-Based Restricted Stock Activity (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitsandShareBasedCompensationSummaryofSharesReservedforFutureIssuanceUnderEquityIncentivePlansDetails" roleURI="http://www.omnicell.com/role/EmployeeBenefitsandShareBasedCompensationSummaryofSharesReservedforFutureIssuanceUnderEquityIncentivePlansDetails">
        <link:definition>2474446 - Disclosure - Employee Benefits and Share-Based Compensation - Summary of Shares Reserved for Future Issuance Under Equity Incentive Plans (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RestructuringExpenses" roleURI="http://www.omnicell.com/role/RestructuringExpenses">
        <link:definition>2175116 - Disclosure - Restructuring Expenses</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RestructuringExpensesTables" roleURI="http://www.omnicell.com/role/RestructuringExpensesTables">
        <link:definition>2376312 - Disclosure - Restructuring Expenses (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RestructuringExpensesNarrativeDetails" roleURI="http://www.omnicell.com/role/RestructuringExpensesNarrativeDetails">
        <link:definition>2477447 - Disclosure - Restructuring Expenses - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RestructuringExpensesTotalRestructuringExpenseRecognizedintheCondensedConsolidatedStatementsofOperationsDetails" roleURI="http://www.omnicell.com/role/RestructuringExpensesTotalRestructuringExpenseRecognizedintheCondensedConsolidatedStatementsofOperationsDetails">
        <link:definition>2478448 - Disclosure - Restructuring Expenses - Total Restructuring Expense Recognized in the Condensed Consolidated Statements of Operations (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
    </xs:appinfo>
  </xs:annotation>
  <xs:element id="omcl_AccountingPoliciesTable" abstract="true" name="AccountingPoliciesTable" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType"/>
  <xs:element id="omcl_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccountsReceivableAndUnbilledReceivables" abstract="false" name="BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccountsReceivableAndUnbilledReceivables" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_SalesTypeLeaseReceivableComponentsTableTextBlock" abstract="false" name="SalesTypeLeaseReceivableComponentsTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="omcl_OtherAssetsCurrentAbstract" abstract="true" name="OtherAssetsCurrentAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="omcl_BusinessCombinationEstimatedNetWorkingCapitalAdjustment" abstract="false" name="BusinessCombinationEstimatedNetWorkingCapitalAdjustment" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedCompensation" abstract="false" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedCompensation" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_HubAndSpokeInnovationsLimitedMember" abstract="true" name="HubAndSpokeInnovationsLimitedMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_ConvertibleNoteHedgeRightsMember" abstract="true" name="ConvertibleNoteHedgeRightsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_DebtInstrumentCovenantTermsAxis" abstract="true" name="DebtInstrumentCovenantTermsAxis" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType"/>
  <xs:element id="omcl_IncreaseDecreaseInOperatingLeaseLiabilities" abstract="false" name="IncreaseDecreaseInOperatingLeaseLiabilities" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_DebtInstrumentRedemptionFaceAmountOfNotesThatMustBeOutstanding" abstract="false" name="DebtInstrumentRedemptionFaceAmountOfNotesThatMustBeOutstanding" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_DebtInstrumentConvertibleLiabilityComponentAbstract" abstract="true" name="DebtInstrumentConvertibleLiabilityComponentAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="omcl_A2009PlanMember" abstract="true" name="A2009PlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_FiniteLivedIntangibleAssetExpectedAmortizationAfterYearFour" abstract="false" name="FiniteLivedIntangibleAssetExpectedAmortizationAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_SharebasedCompensationArrangementbySharebasedPaymentAwardFairValueAssumptionsEstimatedForfeitureRate" abstract="false" name="SharebasedCompensationArrangementbySharebasedPaymentAwardFairValueAssumptionsEstimatedForfeitureRate" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="omcl_LesseeOperatingLeaseLeaseAssumptionsTableTextBlock" abstract="false" name="LesseeOperatingLeaseLeaseAssumptionsTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="omcl_DebtInstrumentCovenantMaximumSecuredNetLeverageRatio" abstract="false" name="DebtInstrumentCovenantMaximumSecuredNetLeverageRatio" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:pureItemType"/>
  <xs:element id="omcl_DeferredTaxAssetConvertibleDebtHedge" abstract="false" name="DeferredTaxAssetConvertibleDebtHedge" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_FDSAmplicareMember" abstract="true" name="FDSAmplicareMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_MeasurementInputRoyaltyRateMember" abstract="true" name="MeasurementInputRoyaltyRateMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_PaymentsforSoftwareForExternalUse" abstract="false" name="PaymentsforSoftwareForExternalUse" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetOfCashAcquired" abstract="false" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetOfCashAcquired" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingAggregateIntrinsicValueAbstract" abstract="true" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingAggregateIntrinsicValueAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="omcl_TechnicalServicesMember" abstract="true" name="TechnicalServicesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_FuturegrantsandawardsMember" abstract="true" name="FuturegrantsandawardsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_AccruedLiabilitiesRebatesCurrent" abstract="false" name="AccruedLiabilitiesRebatesCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_A1997EmployeeStockPurchasePlanMember" abstract="true" name="A1997EmployeeStockPurchasePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_DebtInstrumentConvertibleConsiderationInExcessAmount" abstract="false" name="DebtInstrumentConvertibleConsiderationInExcessAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseLiabilities" abstract="false" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseLiabilities" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_ConnectedDevicesSoftwareLicensesAndOtherMember" abstract="true" name="ConnectedDevicesSoftwareLicensesAndOtherMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageRemainingTermAbstract" abstract="true" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageRemainingTermAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="omcl_LossContingencyExpenseExcludingInsuranceRecoveries" abstract="false" name="LossContingencyExpenseExcludingInsuranceRecoveries" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_LossContingencyExpense" abstract="false" name="LossContingencyExpense" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageRemainingTermAbstract" abstract="true" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageRemainingTermAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="omcl_ProceedsFromPaymentsForCustomerFundsNet" abstract="false" name="ProceedsFromPaymentsForCustomerFundsNet" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_BusinessCombinationAcquiredIntangibleAssetsMeasurementInput" abstract="false" name="BusinessCombinationAcquiredIntangibleAssetsMeasurementInput" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:pureItemType"/>
  <xs:element id="omcl_WellsFargoSecuritiesLLCCitizensBankNAAndJPMorganChaseBankNAMember" abstract="true" name="WellsFargoSecuritiesLLCCitizensBankNAAndJPMorganChaseBankNAMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_RevenueFromContractWithCustomerTimingAndClassificationOfRevenueCategoriesTableTextBlock" abstract="false" name="RevenueFromContractWithCustomerTimingAndClassificationOfRevenueCategoriesTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="omcl_DebtInstrumentCovenantPeriod1Member" abstract="true" name="DebtInstrumentCovenantPeriod1Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_ConvertibleSeniorNotesMember" abstract="true" name="ConvertibleSeniorNotesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_PropertyAndEquipmentTransferredToInventory" abstract="false" name="PropertyAndEquipmentTransferredToInventory" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_BusinessCombinationBasePurchasePrice" abstract="false" name="BusinessCombinationBasePurchasePrice" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherAssetsCurrent" abstract="false" name="BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherAssetsCurrent" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_BusinessCombinationAdjustmentPurchasePriceAdjustment" abstract="false" name="BusinessCombinationAdjustmentPurchasePriceAdjustment" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_DebtInstrumentCovenantTermsDomain" abstract="true" name="DebtInstrumentCovenantTermsDomain" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_LesseeOperatingLeaseSupplementalCashFlowInformationTableTextBlock" abstract="false" name="LesseeOperatingLeaseSupplementalCashFlowInformationTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="omcl_AccruedGroupPurchasingOrganizationFees" abstract="false" name="AccruedGroupPurchasingOrganizationFees" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentDeferredTaxLiabilityNoncurrent" abstract="false" name="BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentDeferredTaxLiabilityNoncurrent" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_DebtInstrumentConvertibleMaximumCash" abstract="false" name="DebtInstrumentConvertibleMaximumCash" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_LondonInterbankOfferingRateLIBORPlus100Member" abstract="true" name="LondonInterbankOfferingRateLIBORPlus100Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_DebtInstrumentCovenantPeriod2Member" abstract="true" name="DebtInstrumentCovenantPeriod2Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_IncreaseDecreaseinPrepaidCommissions" abstract="false" name="IncreaseDecreaseinPrepaidCommissions" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_AdjustmentsToAdditionalPaidInCapitalConvertibleNoteHedge" abstract="false" name="AdjustmentsToAdditionalPaidInCapitalConvertibleNoteHedge" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_HardwareAndSoftwareMember" abstract="true" name="HardwareAndSoftwareMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_DebtInstrumentConvertibleNumberOfSharesIssuable" abstract="false" name="DebtInstrumentConvertibleNumberOfSharesIssuable" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="omcl_SalesTypeAndDirectFinancingLeasesLeaseReceivableToBeReceivedAfterYearFour" abstract="false" name="SalesTypeAndDirectFinancingLeasesLeaseReceivableToBeReceivedAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_ScheduleofSharebasedCompensationFutureIssuanceofSharesTableTextBlock" abstract="false" name="ScheduleofSharebasedCompensationFutureIssuanceofSharesTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="omcl_LesseeOperatingLeaseLiabilityToBePaidAfterYearFour" abstract="false" name="LesseeOperatingLeaseLiabilityToBePaidAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_ConsumablesMember" abstract="true" name="ConsumablesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_AccountingPoliciesLineItems" abstract="true" name="AccountingPoliciesLineItems" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="omcl_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionMaximumPeriod" abstract="false" name="RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionMaximumPeriod" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="omcl_IncrementalLoanFacilityMember" abstract="true" name="IncrementalLoanFacilityMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccruedLiabilities" abstract="false" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccruedLiabilities" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_DebtInstrumentConvertiblePrincipalAmountOfNotesMinimum" abstract="false" name="DebtInstrumentConvertiblePrincipalAmountOfNotesMinimum" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalGrantsBasedOnPerformanceAchievement" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalGrantsBasedOnPerformanceAchievement" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="omcl_ReCeptHoldingsIncMember" abstract="true" name="ReCeptHoldingsIncMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_BusinessCombinationEstimatedClosingCash" abstract="false" name="BusinessCombinationEstimatedClosingCash" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_GroupPurchasingOrganizationFees" abstract="false" name="GroupPurchasingOrganizationFees" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseRightOfUseAssets" abstract="false" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseRightOfUseAssets" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_ShareBasedPaymentArrangementAwardExcludingOptionCostNotYetRecognizedAmount" abstract="false" name="ShareBasedPaymentArrangementAwardExcludingOptionCostNotYetRecognizedAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_RestrictedStockAwardsRSAsAndRestrictedStockUnitsRSUsMember" abstract="true" name="RestrictedStockAwardsRSAsAndRestrictedStockUnitsRSUsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_MarkeTouchMediaLLCMember" abstract="true" name="MarkeTouchMediaLLCMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsPurchasedInPeriodWeightedAveragePrice" abstract="false" name="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsPurchasedInPeriodWeightedAveragePrice" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType"/>
  <xs:element id="omcl_ContractWithCustomerLiabilityCustomerAdvancesAndDepositsCurrent" abstract="false" name="ContractWithCustomerLiabilityCustomerAdvancesAndDepositsCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_The2016RepurchaseProgramMember" abstract="true" name="The2016RepurchaseProgramMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_ContractwithCustomerLiabilityCurrentGross" abstract="false" name="ContractwithCustomerLiabilityCurrentGross" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_CustomerFundLiabilityCurrent" abstract="false" name="CustomerFundLiabilityCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_FiniteLivedIntangibleAssetsCurrencyTranslationAdjustments.IncreaseDecrease" abstract="false" name="FiniteLivedIntangibleAssetsCurrencyTranslationAdjustments.IncreaseDecrease" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_LeaseReceivableMember" abstract="true" name="LeaseReceivableMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_ScheduleOfInterestExpenseDebtTableTextBlock" abstract="false" name="ScheduleOfInterestExpenseDebtTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="omcl_ConvertibleDebtSecuritiesAndWarrantsMember" abstract="true" name="ConvertibleDebtSecuritiesAndWarrantsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_USGovernmentHospitalsMember" abstract="true" name="USGovernmentHospitalsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsPurchased" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsPurchased" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="omcl_A2014ShareRepurchaseProgramMember" abstract="true" name="A2014ShareRepurchaseProgramMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="omcl_DebtInstrumentAccordionFeatureIncreaseLimit" abstract="false" name="DebtInstrumentAccordionFeatureIncreaseLimit" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="omcl_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalGrantsBasedOnPerformanceAchievementWeightedAverageGrantDateFairValue" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalGrantsBasedOnPerformanceAchievementWeightedAverageGrantDateFairValue" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType"/>
  <xs:element id="omcl_A2016and2014ShareRepurchaseProgramsMember" abstract="true" name="A2016and2014ShareRepurchaseProgramsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
</xs:schema>
