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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934
(Amendment No. 1)*

DexCom, Inc.

(Name of Issuer)

Common Stock, $.0001 par value

(Title of Class of Securities)

252131107

(CUSIP Number)

December 31, 2006

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

     o Rule 13d-1(b)

     o Rule 13d-1(c)

     þ Rule 13d-1(d)

* The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

CUSIP No. 252131107  Page 2  of  25

1	NAMES OF REPORTING PERSONS:
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):
	Canaan Equity II L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS):
	(a)   o
	(b)   þ
3	SEC USE ONLY:
4	CITIZENSHIP OR PLACE OF ORGANIZATION:
	Delaware Limited Partnership
		5	SOLE VOTING POWER:
NUMBER OF			0
SHARES		6	SHARED VOTING POWER:
BENEFICIALLY
OWNED BY			See Item 5.
EACH		7	SOLE DISPOSITIVE POWER:
REPORTING
PERSON			0
WITH:		8	SHARED DISPOSITIVE POWER:
			See Item 5.
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:
	See Item 5.
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):
	o
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9):
	See Item 5.
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):
	PN

CUSIP No. 252131107  Page 3  of  25

1	NAMES OF REPORTING PERSONS:
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):
	Canaan Equity II L.P. (QP)
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS):
	(a)   o
	(b)   þ
3	SEC USE ONLY:
4	CITIZENSHIP OR PLACE OF ORGANIZATION:
	Delaware Limited Partnership
		5	SOLE VOTING POWER:
NUMBER OF			0
SHARES		6	SHARED VOTING POWER:
BENEFICIALLY
OWNED BY			See Item 5.
EACH		7	SOLE DISPOSITIVE POWER:
REPORTING
PERSON			0
WITH:		8	SHARED DISPOSITIVE POWER:
			See Item 5.
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:
	See Item 5.
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):
	o
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9):
	See Item 5.
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):
	PN

CUSIP No. 252131107  Page 4  of  25

1	NAMES OF REPORTING PERSONS:
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):
	Canaan Equity II Entrepreneurs LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS):
	(a)   o
	(b)   þ
3	SEC USE ONLY:
4	CITIZENSHIP OR PLACE OF ORGANIZATION:
	Delaware Limited Liability Company
		5	SOLE VOTING POWER:
NUMBER OF			0
SHARES		6	SHARED VOTING POWER:
BENEFICIALLY
OWNED BY			See Item 5.
EACH		7	SOLE DISPOSITIVE POWER:
REPORTING
PERSON			0
WITH:		8	SHARED DISPOSITIVE POWER:
			See Item 5.
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:
	See Item 5.
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):
	o
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9):
	See Item 5.
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):
	OO

CUSIP No. 252131107  Page 5  of  25

1	NAMES OF REPORTING PERSONS:
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):
	Canaan Equity Partners II LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS):
	(a)   o
	(b)   þ
3	SEC USE ONLY:
4	CITIZENSHIP OR PLACE OF ORGANIZATION:
	Delaware Limited Liability Company
		5	SOLE VOTING POWER:
NUMBER OF			0
SHARES		6	SHARED VOTING POWER:
BENEFICIALLY
OWNED BY			See Item 5.
EACH		7	SOLE DISPOSITIVE POWER:
REPORTING
PERSON			0
WITH:		8	SHARED DISPOSITIVE POWER:
			See Item 5.
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:
	See Item 5.
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):
	o
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9):
	See Item 5.
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):
	OO

CUSIP No. 252131107  Page 6  of  25

1	NAMES OF REPORTING PERSONS:
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):
	Stephen L. Green
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS):
	(a)   o
	(b)   þ
3	SEC USE ONLY:
4	CITIZENSHIP OR PLACE OF ORGANIZATION:
	United States
		5	SOLE VOTING POWER:
NUMBER OF			0
SHARES		6	SHARED VOTING POWER:
BENEFICIALLY
OWNED BY			See Item 5.
EACH		7	SOLE DISPOSITIVE POWER:
REPORTING
PERSON			0
WITH:		8	SHARED DISPOSITIVE POWER:
			See Item 5.
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:
	See Item 5.
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):
	o
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9):
	See Item 5.
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):
	IN

CUSIP No. 252131107  Page 7  of  25

1	NAMES OF REPORTING PERSONS:
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):
	Deepak Kamra
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS):
	(a)   o
	(b)   þ
3	SEC USE ONLY:
4	CITIZENSHIP OR PLACE OF ORGANIZATION:
	United States
		5	SOLE VOTING POWER:
NUMBER OF			0
SHARES		6	SHARED VOTING POWER:
BENEFICIALLY
OWNED BY			See Item 5.
EACH		7	SOLE DISPOSITIVE POWER:
REPORTING
PERSON			0
WITH:		8	SHARED DISPOSITIVE POWER:
			See Item 5.
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:
	See Item 5.
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):
	o
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9):
	See Item 5.
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):
	IN

CUSIP No. 252131107  Page 8  of  25

1	NAMES OF REPORTING PERSONS:
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):
	Gregory Kopchinsky
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS):
	(a)   o
	(b)   þ
3	SEC USE ONLY:
4	CITIZENSHIP OR PLACE OF ORGANIZATION:
	United States
		5	SOLE VOTING POWER:
NUMBER OF			0
SHARES		6	SHARED VOTING POWER:
BENEFICIALLY
OWNED BY			See Item 5.
EACH		7	SOLE DISPOSITIVE POWER:
REPORTING
PERSON			0
WITH:		8	SHARED DISPOSITIVE POWER:
			See Item 5.
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:
	See Item 5.
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):
	o
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9):
	See Item 5.
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):
	IN

CUSIP No. 252131107  Page 9  of  25

1	NAMES OF REPORTING PERSONS:
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):
	Guy M. Russo
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS):
	(a)   o
	(b)   þ
3	SEC USE ONLY:
4	CITIZENSHIP OR PLACE OF ORGANIZATION:
	United States
		5	SOLE VOTING POWER:
NUMBER OF			0
SHARES		6	SHARED VOTING POWER:
BENEFICIALLY
OWNED BY			See Item 5.
EACH		7	SOLE DISPOSITIVE POWER:
REPORTING
PERSON			0
WITH:		8	SHARED DISPOSITIVE POWER:
			See Item 5.
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:
	See Item 5.
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):
	o
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9):
	See Item 5.
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):
	IN

CUSIP No. 252131107  Page 10  of  25

1	NAMES OF REPORTING PERSONS:
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):
	John V. Balen
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS):
	(a)   o
	(b)   þ
3	SEC USE ONLY:
4	CITIZENSHIP OR PLACE OF ORGANIZATION:
	United States
		5	SOLE VOTING POWER:
NUMBER OF			0
SHARES		6	SHARED VOTING POWER:
BENEFICIALLY
OWNED BY			See Item 5.
EACH		7	SOLE DISPOSITIVE POWER:
REPORTING
PERSON			0
WITH:		8	SHARED DISPOSITIVE POWER:
			See Item 5.
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:
	See Item 5.
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):
	o
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9):
	See Item 5.
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):
	IN

CUSIP No. 252131107  Page 11  of  25

1	NAMES OF REPORTING PERSONS:
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):
	Eric A. Young
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS):
	(a)   o
	(b)   þ
3	SEC USE ONLY:
4	CITIZENSHIP OR PLACE OF ORGANIZATION:
	United States
		5	SOLE VOTING POWER:
NUMBER OF			0
SHARES		6	SHARED VOTING POWER:
BENEFICIALLY
OWNED BY			See Item 5.
EACH		7	SOLE DISPOSITIVE POWER:
REPORTING
PERSON			0
WITH:		8	SHARED DISPOSITIVE POWER:
			See Item 5.
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:
	See Item 5.
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):
	o
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9):
	See Item 5.
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):
	IN

CUSIP No. 252131107  Page 12  of  25

1	NAMES OF REPORTING PERSONS:
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):
	Charmers Landing LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS):
	(a)   o
	(b)   þ
3	SEC USE ONLY:
4	CITIZENSHIP OR PLACE OF ORGANIZATION:
	Delaware Limited Liability Company
		5	SOLE VOTING POWER:
NUMBER OF			0
SHARES		6	SHARED VOTING POWER:
BENEFICIALLY
OWNED BY			See Item 5.
EACH		7	SOLE DISPOSITIVE POWER:
REPORTING
PERSON			0
WITH:		8	SHARED DISPOSITIVE POWER:
			See Item 5.
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:
	See Item 5.
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):
	o
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9):
	See Item 5.
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):
	OO

CUSIP No. 252131107  Page 13  of  25

1	NAMES OF REPORTING PERSONS:
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):
	Stonehenge LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS):
	(a)   o
	(b)   þ
3	SEC USE ONLY:
4	CITIZENSHIP OR PLACE OF ORGANIZATION:
	Delaware Limited Liability Company
		5	SOLE VOTING POWER:
NUMBER OF			0
SHARES		6	SHARED VOTING POWER:
BENEFICIALLY
OWNED BY			See Item 5.
EACH		7	SOLE DISPOSITIVE POWER:
REPORTING
PERSON			0
WITH:		8	SHARED DISPOSITIVE POWER:
			See Item 5.
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:
	See Item 5.
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):
	o
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9):
	See Item 5.
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):
	OO

CUSIP No. 252131107  Page 14  of  25

1	NAMES OF REPORTING PERSONS:
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):
	Waubeeka LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS):
	(a)   o
	(b)   þ
3	SEC USE ONLY:
4	CITIZENSHIP OR PLACE OF ORGANIZATION:
	Delaware Limited Liability Company
		5	SOLE VOTING POWER:
NUMBER OF			0
SHARES		6	SHARED VOTING POWER:
BENEFICIALLY
OWNED BY			See Item 5.
EACH		7	SOLE DISPOSITIVE POWER:
REPORTING
PERSON			0
WITH:		8	SHARED DISPOSITIVE POWER:
			See Item 5.
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:
	See Item 5.
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS):
	o
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9):
	See Item 5.
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS):
	OO

CUSIP No. 252131107  Page 15  of  25

Item 1(a). Name of Issuer

DexCom, Inc.

Item 1(b). Address of Issuer’s Principal Executive Offices

5555 Oberlin Drive
San Diego, CA 92121

Item 2(a). Name of Person Filing

This statement is filed by (i) Canaan Equity II L.P. (“CE II”), a Delaware limited partnership, (ii) Canaan Equity II L.P. (QP) (“CE II QP”), a Delaware limited partnership, (iii) Canaan Equity II Entrepreneurs, LLC (“Entrepreneurs”), a Delaware limited liability company, (iv) Canaan Equity Partners II LLC (“CEP II”), a Delaware limited liability company and the general partner of CE II and CE II QP and the manager of Entrepreneurs, (v) John V. Balen, (vi) Stephen L. Green, (vii) Deepak Kamra, (viii) Gregory Kopchinsky, (ix) Guy M. Russo, (x) Eric A. Young, (xi) Charmers Landing LLC (“Charmers”), a Delaware limited liability company, (xii) Stonehenge LLC (“Stonehenge”), a Delaware limited liability company, and (xiii) Waubeeka LLC (“Waubeeka”) a Delaware limited liability company. The sole managers of Charmers, Stonehenge, and Waubeeka are Messrs. Green, Kopchinsky and Russo, respectively. We refer to the individuals and entities identified in (i)-(xiii) above collectively as the “Reporting Persons.”

Item 2(b). Address of Principal Business Office or, if None, Residence

Except in the case of Messrs. Balen, Kamra and Young, the principal business address of the Reporting Persons is 285 Riverside Avenue, Suite 205, Westport, CT 06880. The principal business address of Messrs. Balen, Kamra and Young is 2765 Sand Hill Road, Menlo Park, CA 94025.

Item 2(c). Citizenship

Each of CE II and CE II QP is a limited partnership organized under the laws of Delaware. Each of Entrepreneurs, CEP II, Charmers, Stonehenge and Waubeeka is a limited liability company organized under the laws of Delaware. Each of the individuals named above is a citizen of the United States.

Item 2(d). Title of Class of Securities

This Schedule 13G report relates to the Common Stock, par value $0.01 per share (“Common Stock”), of DexCom, Inc.

Item 2(e). CUSIP Number

CUSIP number 252131107

Item 3. If this statement is filed pursuant to §§240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:

(a)	o Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o).
(b)	o Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).
(c)	o Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c).
(d)	o Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C 80a-8).
(e)	o An investment adviser in accordance with §240.13d-1(b)(1)(ii)(E);

CUSIP No. 252131107  Page 16  of  25

(f)	o An employee benefit plan or endowment fund in accordance with §240.13d-1(b)(1)(ii)(F);
(g)	o A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	o A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	o A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	o Group, in accordance with §240.13d-1(b)(1)(ii)(J).

None.

Item 4. Ownership

(a)	Amount Beneficially Owned
	See Item 5.
(b)	Percent of Class:
	Each Reporting Person: %.

CE II	See Item 5.
CE II QP	See Item 5.
Entrepreneurs	See Item 5.
CEP II	See Item 5.
John V. Balen	See Item 5.
Stephen L. Green	See Item 5.
Deepak Kamra	See Item 5.
Gregory Kopchinsky	See Item 5.
Guy M. Russo	See Item 5.
Eric A. Young	See Item 5.
Charmers	See Item 5.
Stonehenge	See Item 5.
Waubeeka	See Item 5.

CUSIP No. 252131107  Page 17  of  25

(c)	Number of shares to which such person has:
(i)	Sole power to vote or direct the vote
(ii)	Shared power to vote or to direct the vote
(iii)	Sole power to dispose or to direct the disposition of
(iv)	Shared power to dispose or to direct the disposition of

None.

Item 5.	Ownership of Five Percent or Less of a Class
	If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following þ.

Item 6.	Ownership of More than Five Percent on Behalf of Another Person
	Not applicable.

Item 7.	Identification and Classification of the Subsidiary which Acquired the Security Being Reported on by the Parent Holding Company
	Not applicable.

Item 8.	Identification and Classification of Members of the Group
	Each of the Reporting Persons expressly disclaims membership in a “Group” as defined in Rule 13d-1 (b) (1) (ii) (J).

Item 9.	Notice of Dissolution of Group
	Not applicable.

Item 10.	Certification
	Not applicable. This Schedule 13G is not filed pursuant to Rule 13d-1(b) or Rule 13d-1(c).

CUSIP No. 252131107  Page 18  of  25

SIGNATURES

After reasonable inquiry and to the best of the undersigned’s knowledge and belief, each of the undersigned certifies that the information set forth in this statement is true, complete and correct.

Dated: February 13, 2007

Canaan Equity II L.P.
By:	Canaan Equity Partners II LLC
	Its General Partner
By:	*
	Manager
Canaan Equity II L.P. (QP)
By:	Canaan Equity Partners II LLC
	Its General Partner
By:	*
	Manager
Canaan Equity II Entrepreneurs LLC.
By:	Canaan Equity Partners II LLC
	Its Manager
By:	*
	Manager
Canaan Equity Partners II LLC
By:	*
	Manager
	*
John V. Balen
	*
Stephen L. Green
	*
Deepak Kamra
	*
Gregory Kopchinsky

CUSIP No. 252131107   Page 19  of  25 

/s/ Guy M. Russo
Guy M. Russo
*
Eric A. Young
Charmers Landing LLC
By:	*
	Manager
Stonehenge LLC
By:	*
	Manager
Waubeeka LLC
By:	/s/ Guy M. Russo
	Manager
* By:	/s/ Guy M. Russo
	Guy M. Russo
	Attorney-in-Fact

This Amendment No. 1 to Schedule 13G was executed by Guy M. Russo pursuant to Powers of Attorney, copies of which are filed herewith as Exhibit 2.
 

CUSIP No. 252131107   Page 20  of  25 

Exhibit 1

Joint Filing Agreement

In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended, the undersigned agree that only one statement containing the information required by Schedule 13G need be filed by each of the undersigned with respect to the ownership by each of the undersigned of shares of stock of DexCom, Inc. This Agreement may be executed in any number of counterparts, each of which shall be deemed an original.

Executed as of February 1, 2006

Canaan Equity II L.P. By:   Canaan Equity Partners II LLC          Its General Partner
By:	*
	Manager
Canaan Equity II L.P. (QP) By:   Canaan Equity Partners II LLC          Its General Partner
By:	*
	Manager
Canaan Equity II Entrepreneurs LLC By:   Canaan Equity Partners II LLC          Its Manager
By:	*
	Manager
Canaan Equity Partners II LLC
By:	*
	Manager
*
John V. Balen
*
James C. Furnivall
*
Stephen L. Green
*
Deepak Kamra

CUSIP No. 252131107  Page 21  of  25

*

Gregory Kopchinsky

/s/ Guy M. Russo

Guy M. Russo

*

Eric A. Young

Charmers Landing LLC

By:	*
	Manager

Stonehenge LLC
By:	*
	Manager
Waubeeka LLC

By:	/s/ Guy M. Russo
	Manager

* By:	/s/ Guy M. Russo
	Guy M. Russo
	Attorney-in-Fact
This Joint Filing Agreement was executed by Guy M. Russo pursuant to Powers of Attorney, copies of which are filed herewith as Exhibit 2.

CUSIP No. 252131107  Page 22  of  25

Exhibit 2

POWER OF ATTORNEY

     KNOW ALL MEN BY THESE PRESENTS, that each person whose signature appears below hereby constitutes and appoints Guy M. Russo his true and lawful attorney-in-fact and agent, with full power of substitution and resubstitution, for him and in his name, place and stead, in any and all capacities (until revoked in writing) to sign any and all instruments, certificates and documents required to be executed on behalf of himself as an individual or in his capacity as a general partner or authorized signatory, as the case may be, on behalf of any of Canaan Equity II L.P., Canaan Equity II L.P. (QP), Canaan Equity II Entrepreneurs LLC and Canaan Equity Partners II LLC pursuant to the Securities Act of 1933, as amended, (the “Securities Act”), or the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and any and all regulations promulgated thereunder and to file the same, with all exhibits thereto, and any other documents in connection therewith, with the Securities and Exchange Commission, and with any other entity when and if such is mandated by the Securities Act, the Exchange Act or by the By-laws of the National Association of Securities Dealers, Inc., granting unto said attorney-in-fact and agent full power and authority to do and perform each and every act and thing requisite and necessary fully to all intents and purposes as he might or could do in person thereby, and ratifying and confirming all that said attorney-in-fact and agent, or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof, or may have done in connection with the matters described above.

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CUSIP No. 252131107   Page 23  of  25 

     IN WITNESS WHEREOF, this Power of Attorney has been signed as of the 14th day of February, 2001.

CANAAN EQUITY II L.P.
By:	Canaan Equity Partners II LLC
	Its General Partner
By:	/s/ Harry T. Rein
	Member/Manager
CANAAN EQUITY II L.P. (QP)
By:	Canaan Equity Partners II LLC
	Its General Partner
By:	/s/ Harry T. Rein
	Member/Manager
CANAAN EQUITY II ENTREPRENEURS LLC
By:	Canaan Equity Partners II LLC
	Its General Partner
By:	/s/ Harry T. Rein
	Member/Manager
CANAAN EQUITY PARTNERS II LLC
By:	/s/ Harry T. Rein
	Member/Manager
/s/ Harry T. Rein
Harry T. Rein
/s/ John V. Balen
John V. Balen
/s/ James C. Furnivall
James C. Furnivall
/s/ Stephen L. Green
Stephen L. Green
/s/ Deepak Kamra
Deepak Kamra
/s/ Guy M. Russo
Guy M. Russo

CUSIP No. 252131107  Page 24  of  25

 /s/ Gregory Kopchinsky Gregory Kopchinsky

 /s/ Eric A. Young Eric A. Young

CUSIP No. 252131107  Page 25  of  25

Exhibit 2

POWER OF ATTORNEY

     KNOW ALL MEN BY THESE PRESENTS, that each entity whose signature appears below hereby constitutes and appoints Guy M. Russo its true and lawful attorney-in-fact and agent, with full power of substitution and resubstitution, for such entity in its name, place and stead, in any and all capacities (until revoked in writing) to sign any and all instruments, certificates and documents required to be executed on behalf of such entity, as applicable pursuant to the Securities Act of 1933, as amended, (the “Securities Act”), or the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and any and all regulations promulgated thereunder and to file the same, with all exhibits thereto, and any other documents in connection therewith, with the Securities and Exchange Commission, and with any other entity when and if such is mandated by the Securities Act, the Exchange Act or by the By-laws of the National Association of Securities Dealers, Inc., granting unto said attorney-in-fact and agent full power and authority to do and perform each and every act and thing requisite and necessary fully to all intents and purposes as he might or could do in person thereby, and ratifying and confirming all that said attorney-in-fact and agent, or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof, or may have done in connection with the matters described above.

IN WITNESS WHEREOF, this Power of Attorney has been signed as of the 11th day of February, 2005.

CHARMERS LANDING LLC
By:	/s/ Stephen L. Green       Manager
STONEHENGE LLC
By:	/s/ Gregory Kopchinsky      Manager