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 * LUCAS DONALD L   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) SAND HILL FINANCIAL COMPANY, 3000 SAND HILL ROAD, BUILDING 3-210 3. Date of Earliest Transaction (Month/Day/Year) 04/20/2005 (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 04/20/2005   G V 14,000 D (6) 73,500 D   Common Stock 04/20/2005   G V 73,500 D (6) 0 D   Common Stock 04/20/2005   G V 73,500 A (6) 216,994 I By the Donald L. Lucas and Lygia S. Lucas Trust U/T/D 12/3/84 (2) Common Stock               95,663 (4) I By the Donald L. Lucas Profit Sharing Trust (1) Common Stock               116,144 (5) I By Sand Hill Financial (3)

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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
LUCAS DONALD L SAND HILL FINANCIAL COMPANY 3000 SAND HILL ROAD, BUILDING 3-210 MENLO PARK, CA 94025	X

Signatures

/s/ Donald L. Lucas		08/18/2005
**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)	Shares are held by Donald L. Lucas Profit Sharing Trust, with respect to which the reporting person is a trustee.
(2)	Shares are held by Donald L. Lucas, TTEE, Donald L. Lucas & Lygia S. Lucas Trust, dated 12/03/84, with respect to which the reporting person is a trustee.
(3)	Mr. Lucas is a general partner of Sand Hill Financial Corporation ("Sand Hill") and disclaims beneficial ownership of shares held by Sand Hill except to his pecuniary interest therein.
(4)	Beneficial holdings increased by 1 share from 95,662 shares to 95,663 shares as a result of rounding inaccuracy due to 2-for-1 reverse stock split upon the closing of the Issuer's initial public offering.
(5)	Beneficial holdings changed from 116,114 shares to 116,144 shares due to typographical error in prior Form 4 report filed on 4/21/05.
(6)	Not applicable.

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