FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person * ACE HEATHER S   2. Issuer Name and Ticker or Trading Symbol DEXCOM INC [DXCM] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) SVP Human Resources (Last) (First) (Middle) 6340 SEQUENCE DRIVE 3. Date of Earliest Transaction (Month/Day/Year) 03/11/2019 (Street) SAN DIEGO, CA 92121 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 03/11/2019   S   2,641 (1) D $ 142.5976 (2) 74,154 (3) D   Common Stock 03/11/2019   S   1,927 (1) D $ 143.5538 (4) 72,227 (3) D   Common Stock 03/11/2019   S   100 (1) D $ 144.09 72,127 (3) D   Common Stock 03/12/2019   S   1,293 (5) D $ 142.7922 70,834 (3) D   Common Stock 03/12/2019   S   4,500 (5) D $ 142.7922 66,334 (3) D

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
ACE HEATHER S 6340 SEQUENCE DRIVE SAN DIEGO, CA 92121			SVP Human Resources

Signatures

By: Timothy O'Brien For: Heather Ace		03/13/2019
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	On August 30, 2018, Ms. Ace adopted a 10b5-1 Plan. This 10b5-1 Plan allows the orderly disposition of shares owned by Ms. Ace. The shares set forth above were sold pursuant to the 10b5-1 Plan.
(2)	This transaction was executed in multiple trades at prices ranging from $142.03 to $143.00. The price above reflects the weighted average sale price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transactions were effected.
(3)	Included in this number are 52,820 unvested restricted stock units, 11,714 of which were granted on March 8, 2019 and shall vest through March 8, 2022, 20,062 of which were granted on March 8, 2018 and shall vest through March 8, 2021, 7,294 of which were granted on March 8, 2017 and shall vest through March 8, 2020 and 13,750 of which were granted on August 22, 2016 and shall vest through August 22, 2020.
(4)	This transaction was executed in multiple trades at prices ranging from $143.03 to $144.00. The price above reflects the weighted average sale price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transactions were effected.
(5)	Represents the number of shares required to be sold by the reporting person to cover tax withholding obligations in connection with the vesting of RSUs. This sale is mandated by the Issuer's election under its equity incentive plans to require the satisfaction of tax withholding obligations to be funded by a "sell to cover" transaction and does not represent a discretionary trade by the reporting person.

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