March 18, 2005


Mail Stop 03-06

Andrew P. Rasdal
President and Chief Executive Officer
DexCom, Inc.
5555 Oberlin Drive
San Diego, California 92121

Re:	DexCom, Inc.
	Amendment No. 3 to Registration Statement on Form S-1
	Filed March 15, 2005
	File No. 333-122454

Dear Mr. Rasdal:

	We have reviewed your filing and have the following comments.
Where indicated, we think you should revise your document in
response
to these comments.  If you disagree, we will consider your
explanation as to why our comment is inapplicable or a revision is
unnecessary.  Please be as detailed as necessary in your
explanation.
In some of our comments, we may ask you to provide us with
supplemental information so we may better understand your
disclosure.
After reviewing this information, we may or may not raise
additional
comments.

	Please understand that the purpose of our review process is
to
assist you in your compliance with the applicable disclosure
requirements and to enhance the overall disclosure in your filing.
We look forward to working with you in these respects.  We welcome
any questions you may have about our comments or on any other
aspect
of our review.  Feel free to call us at the telephone numbers
listed
at the end of this letter.

Amendment No. 3 to Form S-1
1. We note your response to comment 3 and revised disclosure on
page
4.  As previously requested, please expand to disclose the
percentage
of patients whose diabetes management involves more than two
finger
sticks per day, if known, or explain that testing at least twice
per
day is uncommon.
2. Please note that we may have further comments when you file
your
legality opinion and any additional exhibits.


      You may contact Patrick Enunwaonye at (202) 824-5529 or Gary
Todd at (202) 942-2862 if you have questions regarding comments on
the financial statements and related matters.  Please contact
Eduardo
Aleman at (202) 824-5661 or me at (202) 942-1880 with any other
questions.

      			Sincerely,



      			Peggy Fisher
						Assistant Director


cc (via facsimile):  Robert A. Freedman, Esq.
		      Charles Ruck, Esq.
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Andrew P. Rasdal
DexCom, Inc.
March 18, 2005
Page 1