content: <?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:com="http://www.sec.gov/edgar/common">
    <headerData>
      <submissionType>144</submissionType>
      <filerInfo>
        <filer>
          <filerCredentials>
            <cik>0001238485</cik>
            <ccc>XXXXXXXX</ccc>
          </filerCredentials>
        </filer>
        <liveTestFlag>LIVE</liveTestFlag>
  
  
      </filerInfo>
    </headerData>
    <formData>
      <issuerInfo>
        <issuerCik>0001093557</issuerCik>
        <issuerName>DEXCOM INC</issuerName>
        <secFileNumber>000-51222</secFileNumber>
        <issuerAddress>
          <com:street1>6340 SEQUENCE DRIVE</com:street1>
          <com:city>SAN DIEGO</com:city>
          <com:stateOrCountry>CA</com:stateOrCountry>
          <com:zipCode>92121</com:zipCode>
        </issuerAddress>
        <issuerContactPhone>8582000200</issuerContactPhone>
        <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>AUGUSTINOS NICHOLAS</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
        <relationshipsToIssuer>
          <relationshipToIssuer>Director</relationshipToIssuer>
        </relationshipsToIssuer>
      </issuerInfo>
      <securitiesInformation>
        <securitiesClassTitle>Common Stock</securitiesClassTitle>
        <brokerOrMarketmakerDetails>
          <name>Fidelity Brokerage Services LLC</name>
          <address>
            <com:street1>245 Summer Street</com:street1>
            <com:city>Boston</com:city>
            <com:stateOrCountry>MA</com:stateOrCountry>
            <com:zipCode>02110</com:zipCode>
          </address>
        </brokerOrMarketmakerDetails>
        <noOfUnitsSold>3976</noOfUnitsSold>
        <aggregateMarketValue>489127.52</aggregateMarketValue>
        <noOfUnitsOutstanding>386373935</noOfUnitsOutstanding>
        <approxSaleDate>12/15/2023</approxSaleDate>
        <securitiesExchangeName>NASDAQ</securitiesExchangeName>
      </securitiesInformation>
      <securitiesToBeSold>
        <securitiesClassTitle>Common Stock</securitiesClassTitle>
        <acquiredDate>05/18/2023</acquiredDate>
        <natureOfAcquisitionTransaction>Vested RSU Grant</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>DEXCOM, INC.</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>3976</amountOfSecuritiesAcquired>
        <paymentDate>05/18/2023</paymentDate>
        <natureOfPayment>N/A</natureOfPayment>
      </securitiesToBeSold>
      <nothingToReportFlagOnSecuritiesSoldInPast3Months>Y</nothingToReportFlagOnSecuritiesSoldInPast3Months>
      <noticeSignature>
        <noticeDate>12/15/2023</noticeDate>
        <planAdoptionDates>
          <planAdoptionDate>09/15/2023</planAdoptionDate>
        </planAdoptionDates>
        <signature>/s/ Myra King, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Nicholas Augustinos</signature>
      </noticeSignature>
    </formData>
  </edgarSubmission>
metadata_documents: [{"type": "144", "sequence": "1", "filename": "primary_doc.xml", "secsgml_size_bytes": 2935}]
text: 144
  0001238485
  XXXXXXXX
  LIVE
  0001093557
  DEXCOM INC
  000-51222
  6340 SEQUENCE DRIVE
  SAN DIEGO
  CA
  92121
  8582000200
  AUGUSTINOS NICHOLAS
  Director
  Common Stock
  Fidelity Brokerage Services LLC
  245 Summer Street
  Boston
  MA
  02110
  3976
  489127.52
  386373935
  12/15/2023
  NASDAQ
  Common Stock
  05/18/2023
  Vested RSU Grant
  DEXCOM, INC.
  N
  3976
  05/18/2023
  N/A
  Y
  12/15/2023
  09/15/2023
  /s/ Myra King, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Nicholas Augustinos