FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF 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 *   TOPOL ERIC 2. Date of Event Requiring Statement (Month/Day/Year) 07/09/2009 3. Issuer Name and Ticker or Trading Symbol DEXCOM INC [DXCM] (Last) (First) (Middle) 6340 SEQUENCE DRIVE 4. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) 5. If Amendment, Date Original Filed(Month/Day/Year) (Street) SAN DIEGO, CA 92121 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 Beneficially Owned

1.Title of Security (Instr. 4) 2. Amount of Securities Beneficially Owned (Instr. 4) 3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 4. Nature of Indirect Beneficial Ownership (Instr. 5)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.			SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
TOPOL ERIC 6340 SEQUENCE DRIVE SAN DIEGO, CA 92121	  X	Â	Â	Â

Signatures

By: John Lister For: Eric Topol		07/14/2009
**Signature of Reporting Person		Date

Explanation of Responses:

No securities are beneficially owned
*	If the form is filed by more than one reporting person, see Instruction 5(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).
  Remarks: CONFIRMING STATEMENT This Statement confirms that the undersigned, Eric Topol, has authorized and designated Steve Pacelli, Jess Roper, and John Lister 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 Steve Pacelli, Jess Roper, and John Lister 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 Steve Pacelli, Jess Roper, and John Lister are not assuming any of the undersigned's responsibilities to comply with Section 16 of the Securities Exchange Act of 1934. Date: July 10, 2009 /s/ ERIC TOPOL Eric Topol, M.D.

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, See Instruction 6 for procedure.

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