Ownership Submission
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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(Print or Type Responses)
1. Name and Address of Reporting Person *
Riolo John
   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)
VP of Quality Assurance
(Last)
(First)
(Middle)
C/O DEXCOM, INC., 5555 OBERLIN DRIVE		 3. Date of Earliest Transaction (Month/Day/Year)
08/02/2007
(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

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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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
Incentive Stock Option (right to buy) $ 7.79 08/02/2007   A   14,323     (1) 08/02/2017 Common Stock 14,323 (2) 14,323 D  
Non-Qualified Stock Option (right to buy) $ 7.79 08/02/2007   A   35,677     (1) 08/02/2017 Common Stock 35,677 (2) 35,677 D  

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
Riolo John
C/O DEXCOM, INC.
5555 OBERLIN DRIVE
SAN DIEGO, CA 92121		       VP of Quality Assurance  

Signatures

 /s/ By: Jess Roper for John Riolo   08/06/2007
**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) The option vests and becomes exercisable as to 1/48th each month beginning one month following the date of grant and become fully vested on the 48th month anniversary of the date of grant.
(2) Not applicable.
 
Remarks:
CONFIRMING STATEMENT

This Statement confirms that the undersigned, John Riolo, has authorized and designated Nooshin Hussainy, Jess Roper, and Steven R. Pacelli to execute and file on the undersigned's behalf all Forms 3, 4, and 5 (including any amendments thereto) that the undersigned may be required to file with the U.S. Securities and Exchange Commission as a result of the undersigned's ownership of or transactions in securities of DexCom, Inc.  The authority of Nooshin Hussainy, Jess Roper, and Steve R. Pacelli under this Statement shall continue until the undersigned is no longer required to file Forms 3, 4, and 5 with regard to the undersigned's ownership of or transactions in securities of DexCom, Inc., unless earlier revoked in writing.  The undersigned acknowledges that Nooshin Hussainy, Jess Roper, and Steven R. Pacelli are not assuming any of the undersigned's responsibilities to comply with Section 16 of the Securities Exchange Act of 1934.
Date:  Aug 2, 2007
/s/ JOHN RIOLO
John Riolo

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