Sec Form 4 Filing - CARNEY SEAN @ DEXCOM INC - 2008-05-19

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 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 CARNEY SEAN 2. Issuer Name and Ticker or Trading Symbol DEXCOM INC [ DXCM] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O WARBURG PINCUS & CO., 466 LEXINGTON AVENUE, 10TH FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 05/19/2008 (Street) NEW YORK, NY10017 4. If Amendment, Date Original Filed (MM/DD/YY) 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 (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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 05/19/2008 A 5,898 A $ 7.63 20,285 D Common Stock 2,221,626 I See Footnote ( 1 ) ( 2 ) Common Stock 37,779 I See Footnote ( 1 ) ( 2 ) Common Stock 26,615 I See Footnote ( 1 ) ( 2 ) Common Stock 6,442 I See Footnote ( 1 ) ( 2 )

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 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 Non-Qualified Stock Option (Right to Buy) $ 7.63 05/19/2008 A 31,464 ( 3 ) 05/19/2018 Common Stock 31,464 ( 4 ) 31,464 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other CARNEY SEAN C/O WARBURG PINCUS & CO. 466 LEXINGTON AVENUE, 10TH FLOOR NEW YORK, NY10017 X Signatures By: Jess Roper For: Sean Carney 05/21/2008 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The stockholder is Warburg Pincus Private Equity VIII, L.P., a Delaware limited partnership, including two affiliated partnerships (collectively "WP VIII"). Warburg Pincus Partners LLC ("WP Partners LLC"), a New York limited liability company, a subsidiary of Warburg Pincus & Co. ("WP"), a New York general partnership, is the sole general partner of WP VIII. Warburg Pincus LLC ("WP LLC"), a New York limited liability company, manages WP VIII. By reason of the provisions of Rule 16a-1 of the Securities Exchange Act of 1934, as amended, WP VIII, WP Partners LLC, WP and WP LLC may be deemed to be the beneficial owners of the referenced shares. WP Partners LLC, WP and WP LLC disclaim beneficial ownership of such securities, except to the extent of any indirect pecuniary interest therein. Sean D. Carney is a parter of WP and a member and managing director of WP LLC. ( 2 )Continued from Footnote 1: As such, Mr. Carney may be deemed to be the beneficial owner (within the meaning of Rule 16a-1 under the Securities Exchange Act of 1934) of an indeterminate portion of the securities beneficially owned by WP Partners LLC, WP, and WP LLC. Mr. Carney is also a member of the board of directors of the Issuer. Mr. Carney disclaims any beneficial ownership of securities reported herein as owned by WP VIII. ( 3 )The option vests and becomes exercisable as to 1/12th each month beginning one month following the date of grant and becomes fully vested on the first anniversary of the date of grant. ( 4 )Not applicable.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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