<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:ns2="http://www.sec.gov/edgar/common">
    <headerData>
        <submissionType>144</submissionType>
        <filerInfo>
            <filer>
                <filerCredentials>
                    <cik>0001700255</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>
                <ns2:street1>6340 Sequence Drive</ns2:street1>
                <ns2:city>San Diego</ns2:city>
                <ns2:stateOrCountry>CA</ns2:stateOrCountry>
                <ns2:zipCode>92121</ns2:zipCode>
            </issuerAddress>
            <issuerContactPhone>(858) 200-0200</issuerContactPhone>
            <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>JACOB LEACH</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
            <relationshipsToIssuer>
                <relationshipToIssuer>Officer</relationshipToIssuer>
            </relationshipsToIssuer>
        </issuerInfo>
        <securitiesInformation>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <brokerOrMarketmakerDetails>
                <name>Morgan Stanley Smith Barney LLC</name>
                <address>
                    <ns2:street1>1 New York Plaza</ns2:street1>
                    <ns2:street2>38th Floor</ns2:street2>
                    <ns2:city>New York</ns2:city>
                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10004</ns2:zipCode>
                </address>
            </brokerOrMarketmakerDetails>
            <noOfUnitsSold>30764</noOfUnitsSold>
            <aggregateMarketValue>3845500.00</aggregateMarketValue>
            <noOfUnitsOutstanding>387635623</noOfUnitsOutstanding>
            <approxSaleDate>04/20/2023</approxSaleDate>
            <securitiesExchangeName>NASD</securitiesExchangeName>
        </securitiesInformation>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>09/08/2018</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted Stock</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>7676</amountOfSecuritiesAcquired>
            <paymentDate>09/08/2018</paymentDate>
            <natureOfPayment>None</natureOfPayment>
        </securitiesToBeSold>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>03/08/2019</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted Stock</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>8720</amountOfSecuritiesAcquired>
            <paymentDate>03/08/2019</paymentDate>
            <natureOfPayment>None</natureOfPayment>
        </securitiesToBeSold>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>03/08/2020</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted Stock</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>7140</amountOfSecuritiesAcquired>
            <paymentDate>03/08/2020</paymentDate>
            <natureOfPayment>None</natureOfPayment>
        </securitiesToBeSold>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>09/08/2019</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted Stock</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>7228</amountOfSecuritiesAcquired>
            <paymentDate>09/08/2019</paymentDate>
            <natureOfPayment>None</natureOfPayment>
        </securitiesToBeSold>
        <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>JACOB LEACH</name>
                <address>
                    <ns2:street1>6340 Sequence Drive</ns2:street1>
                    <ns2:city>San Diego</ns2:city>
                    <ns2:stateOrCountry>CA</ns2:stateOrCountry>
                    <ns2:zipCode>92121</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>COMMON</securitiesClassTitle>
            <saleDate>03/10/2023</saleDate>
            <amountOfSecuritiesSold>16109</amountOfSecuritiesSold>
            <grossProceeds>1794512.00</grossProceeds>
        </securitiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>JACOB LEACH</name>
                <address>
                    <ns2:street1>6340 Sequence Drive</ns2:street1>
                    <ns2:city>San Diego</ns2:city>
                    <ns2:stateOrCountry>CA</ns2:stateOrCountry>
                    <ns2:zipCode>92121</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>COMMON</securitiesClassTitle>
            <saleDate>03/06/2023</saleDate>
            <amountOfSecuritiesSold>18144</amountOfSecuritiesSold>
            <grossProceeds>2081806.00</grossProceeds>
        </securitiesSoldInPast3Months>
        <noticeSignature>
            <noticeDate>04/20/2023</noticeDate>
            <planAdoptionDates>
                <planAdoptionDate>12/05/2022</planAdoptionDate>
            </planAdoptionDates>
            <signature>/s/ Jacob S Leach</signature>
        </noticeSignature>
    </formData>
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144
0001700255
XXXXXXXX
LIVE
0001093557
DEXCOM INC.
000-51222
6340 Sequence Drive
San Diego
CA
92121
(858) 200-0200
JACOB LEACH
Officer
Common
Morgan Stanley Smith Barney LLC
1 New York Plaza
38th Floor
New York
NY
10004
30764
3845500.00
387635623
04/20/2023
NASD
Common
09/08/2018
Restricted Stock
Issuer
N
7676
09/08/2018
None
Common
03/08/2019
Restricted Stock
Issuer
N
8720
03/08/2019
None
Common
03/08/2020
Restricted Stock
Issuer
N
7140
03/08/2020
None
Common
09/08/2019
Restricted Stock
Issuer
N
7228
09/08/2019
None
N
JACOB LEACH
6340 Sequence Drive
San Diego
CA
92121
COMMON
03/10/2023
16109
1794512.00
JACOB LEACH
6340 Sequence Drive
San Diego
CA
92121
COMMON
03/06/2023
18144
2081806.00
04/20/2023
12/05/2022
/s/ Jacob S Leach