Document:

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                                                                Exhibit 10.15(a)

January 1, 2002

Thomas Meyer
Disetronic Handels AG
Disetronic Medical Systems AG
Brunnmattstrasse 6, Pf 480
CH-3401Burgdorf
Switzerland

Re:  International Distributor Agreement between TheraSense, Inc. and Disetronic
     Handels AG effective September 13, 2000 (the "Agreement")

Dear Thomas,

     This letter is to confirm our agreement with your requested assignment of
the Agreement from Disetronic Handels AG to Disetronic Medical Systems AG. The
requested assignment shall be effective as of September 13, 2000.

     Please return an executed copy of this letter to my attention.

                                  Sincerely,

                                  /s/ LARRY HUFFMAN

                                  Larry Huffman

Acknowledged and Agreed:

Disetronic Handels AG                       Disetronic Medical Systems AG

By: /s/ THOMAS MEYER                        By: /s/ THOMAS MEYER
   -------------------------------          -------------------------------
         Thomas Meyer                                Thomas Meyer

Title:          CEO                         Title:        CEO
       ---------------------------                -------------------------

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                                  AMENDMENT TO

                       INTERNATIONAL DISTRIBUTOR AGREEMENT

     THIS AMENDMENT TO INTERNATIONAL DISTRIBUTOR AGREEMENT (the "Amendment") is
entered into effective January 1, 2002 (the "Amendment Effective Date") by and
between TheraSense, Inc., a Delaware corporation with a principal place of
business at 1360 South Loop Road, Alameda, California 94502, USA ("TheraSense"),
and Disetronic Medical Systems AG, a corporation organized under the laws of
Switzerland with a principal place of business at Brunnmattstrasse 6 CH-3401
Burgdorf, Switzerland ("Disetronic"). Unless otherwise defined herein, all
capitalized terms used in this Amendment shall have the meaning given to them in
the International Distributor Agreement between TheraSense and Disetronic
effective September 13, 2000 (the "Agreement").

     WHEREAS, the parties hereto entered into the Agreement pursuant to which,
among other things, Disetronic distributes TheraSense's FreeStyle Products.

     WHEREAS, the parties desire to amend the Agreement pursuant to this
Amendment so that Disetronic can sell FreeStyle Products in additional
countries.

     NOW, THEREFORE, in consideration of the mutual promises contained herein,
the parties agree as follows:

  1. European Territory. Section 1.12.1 of the Agreement shall be amended and
     restated in its entirety to read as follows:

              "1.12.1 'FreeStyle Territory' shall mean Switzerland, Germany,
                       -------------------
              Austria, The Netherlands, Denmark, Sweden, Norway, Finland,
              Belgium, Italy and France."

  2. Payment. Section 1.19 of the Agreement shall be amended and restated in its
     entirety to read as follows:

              "1.19 'Payment' shall mean the lesser of (i) [***] or (ii) [***]
                     -------
              Disetronic's [***] over the last [***] immediately preceding
              termination of this Agreement."

  3. Exhibit A. Exhibit A to the Agreement shall be amended and restated in its
     entirety to read as set forth on Exhibit A to this Amendment.

*** Confidential Treatment Requested

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  4.  Exhibit B. Exhibit B to the Agreement shall be amended and restated in its
      entirety to read as set forth on Exhibit B to this Amendment.

  5.  Exhibit C. Exhibit C to the Agreement shall be amended and restated in its
      entirety to read as set forth on Exhibit C to this Amendment.

  6.  Term. Section 13.1 of the Agreement shall be amended and restated in its
      entirety to read as follows:

          "13.1 Initial Term. The initial term of this Agreement shall commence
                ------------
          on the Effective Date and shall continue in force until December 31,
          2006, unless terminated earlier under the provisions of this Article
          13 (the "Initial Term"). At the end of the Initial Term, this
          Agreement shall automatically renew for subsequent two (2) year terms
          unless written notice of termination is given by either party to the
          other party at least one (1) year prior to the Agreement's
          then-current expiration date. If Disetronic annual [***] from
          TheraSense for any calendar year prior to [***] exceed [***], then the
          Initial Term of this Agreement shall continue in force until December
          31, 2008."

  7.  Launch. Disetronic shall use diligent efforts to prepare and to receive
      reimbursement in [***] as well as to commence commercial sales of
      FreeStyle Products in the respective countries as soon as the registration
      and reimbursement are achieved. TheraSense shall be responsible for
      obtaining the IVD-CE Mark for the meters and strips to be sold in [***].
      At TheraSense's request, Disetronic shall provide reasonable assistance to
      TheraSense in obtaining the CE Mark. If the registration for [***] is not
      reached before [***], the revision of the minimum quantities for the
      following years will be discussed. Any revision will be made upon mutual
      agreement. Disetronic shall further use diligent efforts to commence
      commercial sales of FreeStyle Products in Belgium through a Subdistributor
      subject to the provisions of Section 2.1.3 and 2.2 of the Agreement as
      soon as possible.

  8.  Subdistributors. Section 2.2 of the Agreement shall be amended and
      restated in its entirety to read as follows:

          "2.2 Subdistributors. Subject to the provisions of Section 2.1.3 and
               ---------------
          this Section 2.2, Disetronic may appoint one or more third parties
          within any portion of the FreeStyle Territory to distribute the
          FreeStyle Products in the Field of Use to Customers. Within ten (10)
          days after the appointment of such Subdistributor, Disetronic shall
          notify TheraSense of the identity of such Subdistributor. Except for
          the case where a Subdistributor is a wholesaler, retailer or
          Affiliate, Disetronic shall not sell or otherwise transfer the
          FreeStyle Products to any Subdistributor until such

*** Confidential Treatment Requested

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          Subdistributor enters into a Subdistributor Agreement. Notwithstanding
          the preceding, [***]. Disetronic shall only grant Subdistributors the
          right to make sales of the FreeStyle Products to Customers in the
          FreeStyle Territory in the Field of Use. Disetronic hereby guarantees
          the performance of each Subdistributor with the provisions set forth
          in this Section 2.2. When Disetronic receives a purchase order from a
          wholesaler or retailer, Disetronic shall include in its
          acknowledgement of such purchase order a statement that the FreeStyle
          Products are not to be repackaged, relabeled, or reshipped outside of
          the European Territory. In the event Disetronic becomes aware, or has
          reason to believe, that a Subdistributor (including a wholesaler or
          retailer) is relabeling, repackaging or reshipping product outside of
          the European Territory (except reshipping to any country within the
          European Union as part of a passive sale), Disetronic shall promptly
          notify TheraSense and shall take corrective action to halt such
          impermissible practice, including without limitation terminating such
          retailer's right to sell FreeStyle Products."

9.   Notice. Pursuant to Section 2.2 of the Agreement Disetronic hereby notifies
     TheraSense that the following Affiliates shall act as Subdistributors in
     the designated portions of the FreeStyle Territory:

     Sweden, Finland, Norway, Denmark: Disetronic Medical Systems AB,
     Nackastrand (Sweden)
     The Netherlands: Disetronic Medical Systems BV, Vianen
     Italy: Disetronic Medical Systems S.R.L., Verona,
     Austria: Disetronic Medical Systems GmbH, Vienna
     France: Disetronic Medical Systems SAS, Emerainville
     USA: Disetronic Medical Systems Inc, St. Paul
     Germany: Disetronic Medical Systems GmbH, Sulzbach and DiaTrade GmbH,
     Sulzbach

10.  Meter Rebate. Upon availability of the co-branded FreeStyle Products
     according to Section 4.7.1 (b) of the Agreement, TheraSense and Disetronic
     shall cooperate in a Meter rebate program in the United States for a period
     of at least [***]. For Meters distributed under this program, TheraSense
     shall lower the transfer price for a System Kit from the price specified in
     Exhibit B to [***] each. The modalities of this program shall be defined in
     a side letter the terms of which are acceptable to both parties.

11.  Agreement. Except as modified hereby, the Agreement shall remain in full
     force and effect in accordance with its terms.

*** Confidential Treatment Requested

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     IN WITNESS WHEREOF, Disetronic and TheraSense have executed this Amendment
by their respective duly authorized representatives.

DISETRONIC MEDICAL SYSTEMS AG           THERASENSE, INC.

By:  /s/  THOMAS MEYER                  By:  /s/  W. MARK LORTZ
   ----------------------------            --------------------------------
     Thomas Meyer                            W. Mark Lortz

Print Name:  Thomas Meyer               Print Name:  W. Mark Lortz
           --------------------                    ------------------------

Title:       CEO                        Title:       CEO
      -------------------------               -----------------------------

                                        Date:        February 8, 2002
                                             ------------------------------

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CONFIDENTIAL                                                      1 January 2002

                                    EXHIBIT A

                               FREESTYLE PRODUCTS

As of the Effective Date, the FreeStyle Products include the following six (6)
products:

1.   "System Kit" shall mean a product that consists of 1 Meter, 10 Strips, 1
      ----------
     Lancing Device, 1 Finger Cap, 10 Lancets, 1 Carrying Case, 1 Log Book, 1
     Quick Reference Card, 1 Owners Booklet; where "Finger Cap" shall mean a cap
                                                    ----------
     for the Lancing Device designed for lancing the fingertip rather than the
     arm.

2.   "Lancet" shall mean a disposable head placed in a lancing device for use in
      ------
     piercing the patient's skin.

3.   "Control Solution" shall mean a glucose solution for testing the operation
      ----------------
     of the FreeStyle Meter and Strips.

4.   "Lancing Device" shall mean a lancing device which is used to bring blood
      --------------
     to the surface of a patient's skin and which is physically separate from
     the Meter.

5.   "Meter" shall mean a meter whose sole function is to coulometrically
      -----
     measure blood glucose levels.

6.   "Strips" shall mean a package of strips which are loaded into the Meter and
      ------
     used to acquire a blood sample of less then 0.4 microliters from the
     surface of a patient's skin. (The Strips are currently offered in packages
     of 50 and 100; such quantities are subject to change.)

The parties recognize that for the countries France and Italy, market
characteristics including desired Meter appearance and certain other
characteristics may differ from other countries in the European Territory.
Therefore, TheraSense shall supply FreeStyle Products for France and Italy which
have a different appearance and branding than the FreeStyle Products sold in the
other countries in the European Territory.

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CONFIDENTIAL                                                      1 January 2002

                                    EXHIBIT B

                                 TRANSFER PRICE

                                 Pricing Details

System Kit
----------

     The price of a System Kit for sale in the FreeStyle Territory is [***]
(includes 1 Meter, 10 Strips, 1 Lancing Device, 1 Finger Cap, 10 Lancets, 1
Carrying Case, 1 Log Book, 1 Quick Reference Card, 1 Owners Booklet).

Strips
------

     The price of Strips ordered for the US Territory is [***].

     The price of Strips ordered for the European Territory is:

--------------------------------------------------------------------------------
           Annual Sales Volume                          Price
            (Number of Strips)                        Per Strip
================================================================================
[***]

Lancing Devices, Lancets and Control Solution
---------------------------------------------

     The following prices are valid for the following products for sale in the
FreeStyle Territory when not purchased as part of a System Kit:

                Lancing devices         [***] per lancing device

                Lancets                 [***] per box of 100 lancets

                Control Solution        [***] per bottle of control solution

*** Confidential Treatment Requested

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CONFIDENTIAL                                                      1 January 2002

                                    EXHIBIT C

          ANNUAL MINIMUM PURCHASE OBLIGATION FOR THE EUROPEAN TERRITORY

--------------------------------------------------------------------------------
           Calendar Year                                   Minimum
                                                      Purchase Obligation
================================================================================
[***]

     In the event that the term of this Agreement is extended pursuant to the
terms of Section 13.1, the minimums shall be:

--------------------------------------------------------------------------------
           Calendar Year                                    Minimum
                                                      Purchase Obligation
================================================================================
[***]

*** Confidential Treatment Requested<PAGE>

                                                                Exhibit 10.20(a)

                                   EXHIBIT B-1

                      AMENDED AND RESTATED PROMISSORY NOTE

$17,500                                                            March 1, 2002

This AMENDED AND RESTATED PROMISSORY NOTE amends and restates in its entirety
the PROMISSORY NOTE dated July 30, 1998 originally delivered by the undersigned
to TheraSense, Inc., a Delaware corporation (the "Company"). Any capitalized
terms not defined herein shall have the meaning given to them in the Repurchase
Agreement between the Company and the undersigned dated July 30, 1998.

For value received, the undersigned promises to pay to the Company, or order, at
its principal office the principal sum of $17,500 without interest. Said
principal shall be due on the earlier of April 6, 2003, or (ii) the
undersigned's termination of employment with or services to the Company.

Should suit be commenced to collect this Note or any portion thereof, such sum
as the Court may deem reasonable shall be added hereto as attorneys' fees. The
maker waives presentment for payment, protest, notice of protest, and notice of
non-payment of this Note.

This Note is secured by a pledge of 62,500 (post-split) shares of Common Stock
of the Company, pursuant to the provisions of the Repurchase Agreement between
the Company and the undersigned executed on July 30, 1998.

The holder of this Note shall have full recourse against the maker, and shall
not be required to proceed against the Shares or other collateral securing this
Note in the event of default.

                                      /s/  CHARLES T. LIAMOS
                                      -----------------------------------------
                                      Charles Liamos

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