EXHIBIT 99.1

CERTIFICATION OF CHIEF EXECUTIVE OFFICER AND
CHIEF FINANCIAL OFFICER PURSUANT TO 18 U.S.C. SECTION 1350,
AS ADOPTED PURSUANT TO
SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

I, W. Mark Lortz, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that the Quarterly Report of TheraSense, Inc. on Form 10-Q for the fiscal quarter ended March 31, 2003 fully complies with the requirements of Section 15(d) of the Securities Exchange Act of 1934 and that information contained in such Quarterly Report on Form 10-Q fairly presents in all material respects the financial condition and results of operations of TheraSense, Inc.

Date: May 14, 2003

By:	/s/ W. MARK LORTZ
Name:	W. Mark Lortz
Title:	Chief Executive Officer

I, Charles T. Liamos, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that the Quarterly Report of TheraSense, Inc. on Form 10-Q for the fiscal quarter ended March 31, 2003 fully complies with the requirements of Section 15(d) of the Securities Exchange Act of 1934 and that information contained in such Quarterly Report on Form 10-Q fairly presents in all material respects the financial condition and results of operations of TheraSense, Inc.

Date: May 14, 2003

By:	/s/ CHARLES T. LIAMOS
Name:	Charles T. Liamos
Title:	Chief Financial Officer