DEXCOM INC — Director's Dealing 2012

May 22, 2012

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: DEXCOM INC (DXCM)
CIK: 0001093557
Period of Report: 2012-05-18

Reporting Person: Balo Andrew K (SVP, Regulatory and Clinical)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2012-05-18	Common Stock	M	28466	$0.5	Acquired	126506	Direct
2012-05-18	Common Stock	S	14198	$10.4584	Disposed	112308	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2012-05-18	Incentive Stock Option (right to buy)	$0.5	M	28466	Disposed	2013-01-30	Common Stock (28466)	Direct

Holdings (Non-Derivative)

Security	Shares	Ownership
Common Stock	7000	Indirect

Footnotes

F1: This transaction was executed in multiple trades at prices ranging from $10.45 to $10.47. The price above reflects the weighted average sale price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issurer full information regarding the number of shares and prices at which the transactions were effected.

F2: Included in this number are 83,062 unvested restricted stock units, 29,312 of which were granted on March 8, 2011 and shall vest through March 8, 2014, and 53,750 of which were granted on March 8, 2012 and shall vest through March 8, 2015.

F3: Shares are held by the Balo Family Trust U/A/D 4/6/2006, with respect to which the reporting person is a trustee.

F4: Not applicable