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 * Ahrens Brenton Karl   2. Issuer Name and Ticker or Trading Symbol DEXCOM INC [DXCM] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director __X__ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) CANAAN PARTNERS, 2765 SAND HILL ROAD 3. Date of Earliest Transaction (Month/Day/Year) 04/19/2005 (Street) MENLO PARK, CA 94025 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 04/19/2005   C   1,733,941 A (1) 1,733,941 I See Footnote (3) Common Stock 04/19/2005   C   1,079,075 A (1) 1,079,075 I See Footnote (3) Common Stock 04/19/2005   C   280,619 A (1) 280,619 I See Footnote (3)

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

Series B Preferred Stock

(1)

04/19/2005

C

3,467,833

(1)

(2)

Common Stock

1,733,941 (1)

(1)

0

I

See Footnote (3)

Series C Preferred Stock

(1)

04/19/2005

C

2,158,152

(1)

(2)

Common Stock

1,079,075 (1)

(1)

0

I

See Footnote (3)

Series D Preferred Stock

(1)

04/19/2005

C

561,240

(1)

(2)

Common Stock

280,619 (1)

(1)

0

I

See Footnote (3)

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Ahrens Brenton Karl CANAAN PARTNERS 2765 SAND HILL ROAD MENLO PARK, CA 94025	X	X

Signatures

John D. Lambrech as Attorney in Fact		04/19/2005
**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)	Each share of the Series B, Series C and Series D Redeemable Convertible Preferred Stock converted automatically into 0.5 shares of Common Stock upon the closing of the Issuers initial public offering of Common Stock pursuant to an effective registration statement filed with the U.S. Securities and Exchange Commission.
(2)	Not Applicable
(3)	The reporting person represents Canaan Equity Partners II LLC, which is the general partner of Canaan Equity II L.P., Canaan Equity II L.P. (QP) and the Manager of Canaan Equity II Entrepreneurs LLC. The reporting person disclaims beneficial ownership of these shares except to his pecuniary interest therein.

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