<SEC-DOCUMENT>0001093557-25-000224.txt : 20250707
<SEC-HEADER>0001093557-25-000224.hdr.sgml : 20250707
<ACCEPTANCE-DATETIME>20250707161509
ACCESSION NUMBER:		0001093557-25-000224
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20250508
FILED AS OF DATE:		20250707
DATE AS OF CHANGE:		20250707

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			GALA RENEE D
		CENTRAL INDEX KEY:			0001607737
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-51222
		FILM NUMBER:		251108190

	MAIL ADDRESS:	
		STREET 1:		C/O JAZZ PHARMACEUTICALS, INC.
		STREET 2:		3170 PORTER DRIVE
		CITY:			PALO ALTO
		STATE:			CA
		ZIP:			94304

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			DEXCOM INC
		CENTRAL INDEX KEY:			0001093557
		STANDARD INDUSTRIAL CLASSIFICATION:	SURGICAL & MEDICAL INSTRUMENTS & APPARATUS [3841]
		ORGANIZATION NAME:           	08 Industrial Applications and Services
		EIN:				330857544
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		6340 SEQUENCE DRIVE
		CITY:			SAN DIEGO
		STATE:			CA
		ZIP:			92121
		BUSINESS PHONE:		8582000200

	MAIL ADDRESS:	
		STREET 1:		6340 SEQUENCE DRIVE
		CITY:			SAN DIEGO
		STATE:			CA
		ZIP:			92121
</SEC-HEADER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>wk-form4a_1751919300.xml
<DESCRIPTION>FORM 4/A
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2025-05-08</periodOfReport>

    <dateOfOriginalSubmission>2025-05-12</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001093557</issuerCik>
        <issuerName>DEXCOM INC</issuerName>
        <issuerTradingSymbol>DXCM</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001607737</rptOwnerCik>
            <rptOwnerName>GALA RENEE D</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>6340 SEQUENCE DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN DIEGO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92121</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2025-05-08</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1161</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6881</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The original Form 4, filed on May 12, 2025, is being amended by this Form 4 to correct a calculation error that misreported the number of unvested restricted stock units granted to the reporting person on May 8, 2025. This amendment correctly reports the number of unvested restricted stock units granted to the reporting person on May 8, 2025.</footnote>
        <footnote id="F2">Represents unvested restricted stock units which were granted on May 8, 2025 and shall vest on the earlier of the one year anniversary of the grant date or the date of DexCom, Inc.'s 2026 Annual Meeting of Stockholders.</footnote>
        <footnote id="F3">Included in this number are 6,881 unvested restricted stock units, 5,720 of which were granted on March 6, 2025 and shall vest through March 6, 2028 and 1,161 of which were granted on May 8,  2025 and shall vest on the earlier of the one year anniversary of the grant date or the date of DexCom, Inc.'s 2026 Annual Meeting of Stockholders.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Jereme M. Sylvain, as Attorney-in-Fact for Renee D. Gala</signatureName>
        <signatureDate>2025-07-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
