<PAGE>

--------------------------------------------------------------------------------
                        WARRANT TO PURCHASE COMMON STOCK
--------------------------------------------------------------------------------

                                                                   Exhibit 10.20

THIS WARRANT AND THE SECURITIES ISSUABLE HEREUNDER HAVE NOT BEEN REGISTERED
UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR ANY STATE SECURITIES LAWS. THEY
MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED OR OTHERWISE TRANSFERRED IN THE
ABSENCE OF AN EFFECTIVE REGISTRATION STATEMENT UNDER SUCH ACT AND ANY APPLICABLE
STATE SECURITIES LAWS OR THE AVAILABILITY OF AN EXEMPTION FROM REGISTRATION
UNDER SUCH ACT AND ANY APPLICABLE STATE SECURITIES LAWS.

                        WARRANT TO PURCHASE COMMON STOCK

     Number of Shares:   Up to [6,000,000] shares (subject to adjustment)

     Warrant Price:      See Section 1.2 Below

     Issuance Date:      January 14, 2004

     Expiration Date:    January 14, 2007

THIS WARRANT CERTIFIES THAT for value received, _______________ or its
registered assigns (hereinafter called the "Holder") is entitled to purchase
from Diametrics Medical, Inc. (hereinafter called the "Company"), the above
referenced number of fully paid and nonassessable shares (the "Shares") of
common stock (the "Common Stock"), of Company, at the Warrant Price per Share
referenced above; the number of shares purchasable upon exercise of this Warrant
referenced above being subject to adjustment from time to time as described
herein. This Warrant is issued in connection with that certain Subscription
Agreement dated as of January 14, 2004, by and between the Company and Holder
(the "Subscription Agreement"). The exercise of this Warrant shall be subject to
the provisions, limitations and restrictions contained herein.

1.   Term and Exercise.

1.1  Term. This Warrant is exercisable in whole or in part (but not as to any
fractional share of Common Stock), at any time and from time to time after the
date all of the Company's Series F Convertible Preferred Stock is converted into
shares of Common Stock but prior to 6:00 p.m. on the Expiration Date set forth
above.

1.2  Warrant Price.

The Warrant shall be exercisable at the lower of (i) the average of the lowest
ten inter-day closing prices of the Common Stock on the Over-the-Counter
Bulletin Board (the "OTC Bulletin Board") during the 10 trading days immediately
preceding the exercise date or (ii) the closing price of the Common Stock on
January 14, 2004. Such ten day period will be extended by the number of trading
days during such period on which (i) trading in the Common Stock is suspended
by, or not traded on the OTC Bulletin Board, (ii) after the date of the date of
the Registration Statement for the underlying Common Stock is declared
ineffective by the Securities and Exchange Commission (the "SEC"), and the
prospectus included in the Registration Statement for the underlying shares of
Common Stock may not be used by the holder for resale of the underlying shares
of Common Stock, or (iii) after the date the Registration Statement for the
underlying shares of Common Stock is declared effective by the SEC, the
prospectus included in the Registration Statement for the underlying shares of
Common Stock may not be used by the holder for the resale of underlying shares
of Common stock of the Series F Convertible Preferred Stock.

1.3  Maximum Number of Shares

The maximum number of Shares of Common Stock exercisable pursuant to this
Warrant is _________ Shares. However, notwithstanding anything herein to the
contrary, in no event shall the Holder be permitted to exercise this Warrant for
a number of Shares greater than the number that would cause the aggregate
beneficial ownership of the Company's Common Stock (calculated pursuant to Rule
13d-3 of the Securities Exchange Act of 1934, as amended) of the Holder and all
persons affiliated with the Holder to equal 9.99% of the Company's Common Stock
then outstanding.

1.4  Procedure for Exercise of Warrant. Holder may exercise this Warrant by
delivering the following to the principal office of the Company in accordance
with Section 5.1 hereof: (i) a duly executed Notice of Exercise in substantially
the form attached as Schedule A, (ii) payment of the Warrant Price then in
effect for each of the Shares being purchased, as designated in the Notice of
Exercise, and (iii) this Warrant. Payment of the Warrant Price may be in cash,
certified or official bank check payable to the order of the Company, or wire
transfer of funds to the Company's account (or any combination of any of the
foregoing) in the amount of the Warrant Price for each share being purchased.
Notwithstanding any provisions herein to the contrary, if the Current Market
Price (as defined below) is greater than the Warrant Price (at the date of
calculation, as set forth below), the Holder may elect to receive, without the
payment by the Holder of any additional consideration, shares of Common Stock
equal to the value of the "spread" on the Shares (or the portion thereof being
canceled) by surrender of this Warrant at the principal office of the Company in
accordance with Section 5.1, together with the Notice of Exercise, in which
event the Company shall issue to the Holder hereof a number of shares of Common
Stock computed using the following formula:

                                X = Y x (CMP-WP)
                                    ------------
                                         CMP

Where:  X   =   the number of shares of Common Stock to be issued to the Holder
                pursuant to this net exercise

        Y   =   the number of shares of Common Stock purchasable under the
                Warrant or, if only a portion of the Warrant is being exercised,
                that portion of the Warrant requested to be exercised

                                                                          Page 1

<PAGE>

        CMP  =  the Current Market Price (as of the date of such calculation) of
                one share of Common Stock

        WP   =  the Warrant Price (as adjusted as of the date of such
                calculation)

For purposes of this Warrant, the "Current Market Price" of one share of Common
Stock as of a particular date shall be determined as follows: (i) if traded on a
national securities exchange or through the Nasdaq Stock Market, the Current
Market Price shall be deemed to be the volume weighted average trading price of
the Common Stock on such exchange as of five business days immediately prior to
the date of exercise indicated in the Notice of Exercise (or if no reported
sales took place on such day, the last date on which any such sales took place
prior to the date of exercise); (ii) if traded over-the-counter but not on the
Nasdaq Stock Market, the Current Market Price shall be deemed to be the average
of the closing bid and asked prices as of five business days immediately prior
to the date of exercise indicated in the Notice of Exercise; and (iii) if there
is no active public market, the Current Market Price shall be the fair market
value of the Common Stock as of the date of exercise, as determined in good
faith by the Board of Directors of the Company.

1.5  Delivery of Certificate and New Warrant. In the event of any exercise of
the rights represented by this Warrant, a certificate or certificates for the
shares of Common Stock so purchased, registered in the name of the Holder or
such other name or names as may be designated by the Holder, together with any
other securities or other property which the Holder is entitled to receive upon
exercise of this Warrant, shall be delivered to the Holder hereof, at the
Company's expense, within a reasonable time, not exceeding fifteen (15) calendar
days, after the rights represented by this Warrant shall have been so exercised;
and, unless this Warrant has expired, a new Warrant representing the number of
Shares (except a remaining fractional share), if any, with respect to which this
Warrant shall not then have been exercised shall also be issued to the Holder
hereof within such time. The person in whose name any certificate for shares of
Common Stock is issued upon exercise of this Warrant shall for all purposes be
deemed to have become the holder of record of such shares on the date on which
the Warrant was surrendered and payment of the Warrant Price was received by the
Company, irrespective of the date of delivery of such certificate, except that,
if the date of such surrender and payment is on a date when the stock transfer
books of the Company are closed, such person shall be deemed to have become the
holder of such Shares at the close of business on the next succeeding date on
which the stock transfer books are open.

1.6  Restrictive Legend. Each certificate for Shares shall bear a restrictive
legend in substantially the form as follows, together with any additional legend
required by (i) any applicable state securities laws and (ii) any securities
exchange upon which such Shares may, at the time of such exercise, be listed:

     "The shares represented by this certificate have not been registered
     under the Securities Act of 1933, as amended and may not be sold,
     offered for sale, transferred or pledged in the absence of such
     registration or an exemption therefrom under such Act."

Any certificate issued at any time in exchange or substitution for any
certificate bearing such legend shall also bear such legend unless, in the
opinion of counsel for the Holder thereof (which counsel shall be reasonably
satisfactory to the Company), the securities represented thereby are not, at
such time, required by law to bear such legend.

1.7  Fractional Shares. No fractional Shares shall be issuable upon exercise or
conversion of the Warrant and the number of Shares to be issued shall be rounded
down to the nearest whole Share. If a fractional share interest arises upon any
exercise or conversion of the Warrant, the Company shall eliminate such
fractional share interest by paying to Holder an amount computed by multiplying
the fractional interest by the Current Market Price of a full Share.

2.   Representations, Warranties and Covenants.

2.1  Representations and Warranties.

     (a)  The Company is a corporation duly organized, validly existing and in
good standing under the laws of its state of incorporation and has all necessary
power and authority to perform its obligations under this Warrant;

     (b)  The execution, delivery and performance of this Warrant has been duly
authorized by all necessary actions on the part of the Company and constitutes
the legal, valid and binding obligation of the Company, enforceable against the
Company in accordance with its terms; and

     (c)  This Warrant does not violate and is not in conflict with any of the
provisions of the Company's Amended and Restated Articles of Incorporation or
Certificate of Designation, Bylaws and any resolutions of the Company's Board of
Directors or stockholders, or any agreement of the Company, and no event has
occurred and no condition or circumstance exists that might (with or without
notice or lapse of time) constitute or result directly or indirectly in such a
violation or conflict.

2.2  Issuance of Shares. The Company covenants and agrees that all shares of
Common Stock that may be issued upon the exercise of the rights represented by
this Warrant will, upon issuance, be validly issued, fully paid and
nonassessable, and free from all taxes, liens and charges with respect to the
issue thereof. The Company further covenants and agrees that it will pay when
due and payable any and all federal and state taxes which may be payable in
respect of the issue of this Warrant or any Common Stock or certificates
therefor issuable upon the exercise of this Warrant. The Company further
covenants and agrees that the Company will at all times have authorized and
reserved, free from preemptive rights, a sufficient number of shares of Common
Stock to provide for the exercise in full of the rights represented by this
Warrant. If at any time the number of authorized but unissued shares of Common
Stock of the Company shall not be sufficient to effect the exercise of the
Warrant in full, subject to the limitations set forth in Section 1.3 hereto,
then the Company will take all such corporate action as may, in the opinion of
counsel to the Company, be necessary or advisable to increase the number of its
authorized shares of Common Stock as shall be sufficient to permit the exercise
of the Warrant in full, subject to the limitations set forth in Section 1.3
hereto, including without limitation, using its best efforts to obtain any
necessary stockholder approval of such increase. The Company further covenants
and agrees that if any shares of capital stock to be reserved for the purpose of
the issuance of shares upon the exercise of this Warrant require registration
with or approval of any governmental authority under any federal or state law
before such shares may be validly issued or delivered upon exercise, then the
Company will in good faith and as expeditiously as possible endeavor to secure
such registration or approval, as the case may be. If and so long as the Common
Stock issuable upon the exercise of this Warrant is listed on any national
securities exchange or the Nasdaq Stock Market, the Company will, if permitted
by the rules of such exchange or market, list and keep listed on such exchange
or market, upon official notice of issuance, all shares of such Common Stock
issuable upon exercise of this Warrant.

3.   Other Adjustments.

3.1  Subdivision or Combination of Shares. In case the Company shall at any time
subdivide its outstanding Common Stock into a greater number of shares, the
Warrant Price in effect immediately prior to such subdivision shall be
proportionately reduced, and conversely, in case the outstanding Common Stock of
the Company shall be combined into a smaller number of shares, the Warrant Price
in effect immediately prior to such combination shall be proportionately
increased.

3.2  Dividends in Common Stock, Other Stock or Property. If at any time or from
time to time the holders of Common Stock (or any shares of stock or other
securities at the time receivable upon the exercise of this Warrant) shall have
received or become entitled to receive, without payment therefor:

     (a)  Common Stock, Options or any shares or other securities which are at
any time directly or indirectly convertible into or exchangeable for Common
Stock, or any rights or options to subscribe for, purchase or otherwise acquire
any of the foregoing by way of dividend or other distribution;

                                                                          Page 2

<PAGE>

     (b)  any cash paid or payable otherwise than as a regular cash dividend; or

     (c)  Common Stock or additional shares or other securities or property
(including cash) by way of spin-off, split-up, reclassification, combination of
shares or similar corporate rearrangement (other than Common Stock issued as a
stock split or adjustments in respect of which shall be covered by the terms of
Section 3.1 above) and additional shares, other securities or property issued in
connection with a Change (as defined below) (which shall be covered by the terms
of Section 3.4 below), then and in each such case, the Holder hereof shall, upon
the exercise of this Warrant, be entitled to receive, in addition to the number
of shares of Common Stock receivable thereupon, and without payment of any
additional consideration therefor, the amount of stock and other securities and
property (including cash in the cases referred to in clause (b) above and this
clause (c)) which such Holder would hold on the date of such exercise had such
Holder been the holder of record of such Common Stock as of the date on which
holders of Common Stock received or became entitled to receive such shares or
all other additional stock and other securities and property.

3.3  Reorganization, Reclassification, Consolidation, Merger or Sale. If any
recapitalization, reclassification or reorganization of the share capital of the
Company, or any consolidation or merger of the Company with another corporation,
or the sale of all or substantially all of its shares and/or assets or other
transaction (including, without limitation, a sale of substantially all of its
assets followed by a liquidation) shall be effected in such a way that holders
of Common Stock shall be entitled to receive shares, securities or other assets
or property (a "Change"), then, as a condition of such Change, lawful and
adequate provisions shall be made by the Company whereby the Holder hereof shall
thereafter have the right to purchase and receive (in lieu of the Common Stock
of the Company immediately theretofore purchasable and receivable upon the
exercise of the rights represented hereby) such shares, securities or other
assets or property as may be issued or payable with respect to or in exchange
for the number of outstanding Common Stock which such Holder would have been
entitled to receive had such Holder exercised this Warrant immediately prior to
the consummation of such Change. The Company or its successor shall promptly
issue to Holder a new Warrant for such new securities or other property. The new
Warrant shall provide for adjustments which shall be as nearly equivalent as may
be practicable to give effect to the adjustments provided for in this Section 3
including, without limitation, adjustments to the Warrant Price and to the
number of securities or property issuable upon exercise of the new Warrant. The
provisions of this Section 3.3 shall similarly apply to successive Changes.

4.   Ownership and Transfer.

4.1  Ownership of This Warrant. The Company may deem and treat the person in
whose name this Warrant is registered as the holder and owner hereof
(notwithstanding any notations of ownership or writing hereon made by anyone
other than the Company) for all purposes and shall not be affected by any notice
to the contrary until presentation of this Warrant for registration of transfer
as provided in this Section 4.

4.2  Transfer and Replacement. This Warrant and all rights hereunder are
transferable in whole or in part upon the books of the Company by the Holder
hereof in person or by duly authorized attorney, and a new Warrant or Warrants,
of the same tenor as this Warrant but registered in the name of the transferee
or transferees (and in the name of the Holder, if a partial transfer is
effected) shall be made and delivered by the Company upon surrender of this
Warrant duly endorsed, at the office of the Company in accordance with Section
5.1 hereof. Upon receipt by the Company of evidence reasonably satisfactory to
it of the loss, theft or destruction, and, in such case, of indemnity or
security reasonably satisfactory to it, and upon surrender of this Warrant if
mutilated, the Company will make and deliver a new Warrant of like tenor, in
lieu of this Warrant; provided that if the Holder hereof is an instrumentality
of a state or local government or an institutional holder or a nominee for such
an instrumentality or institutional holder an irrevocable agreement of indemnity
by such Holder shall be sufficient for all purposes of this Warrant, and no
evidence of loss or theft or destruction shall be necessary. This Warrant shall
be promptly cancelled by the Company upon the surrender hereof in connection
with any transfer or replacement. Except as otherwise provided above, in the
case of the loss, theft or destruction of a Warrant, the Company shall pay all
expenses, taxes and other charges payable in connection with any transfer or
replacement of this Warrant, other than income taxes and stock transfer taxes
(if any) payable in connection with a transfer of this Warrant, which shall be
payable by the Holder. Holder will not transfer this Warrant and the rights
hereunder except in compliance with federal and state securities laws and except
after providing evidence of such compliance reasonably satisfactory to the
Company.

5.   Miscellaneous Provisions.

5.1  Notices. Any notice or other document required or permitted to be given or
delivered to the Holder shall be delivered or forwarded to the Holder at c/o
Mercator Group, LLC, 555 South Flower Street, Suite 4500, Los Angeles,
California 90071, Attention: President (Facsimile No. 213/553-8285, or to such
other address or number as shall have been furnished to the Company in writing
by the Holder. Any notice or other document required or permitted to be given or
delivered to the Company shall be delivered or forwarded to the Company at 3050
Centre Pointe Road, Minnesota 55113, Attention: Chief Financial Officer
(Facsimile No. 651/638-1197), with a copy to Dorsey & Whitney LLP, 50 South
Sixth Street, Suite 1500, Minneapolis, Minnesota 55402, Attention: Kenneth L.
Cutler, Esq. (Facsimile No. 612/340-7800), or to such other address or number as
shall have been furnished to Holder in writing by the Company.

5.2  All notices, requests and approvals required by this Warrant shall be in
writing and shall be conclusively deemed to be given (i) when hand-delivered to
the other party, (ii) when received if sent by facsimile at the address and
number set forth above; provided that notices given by facsimile shall not be
effective, unless either (a) a duplicate copy of such facsimile notice is
promptly given by depositing the same in the mail, postage prepaid and addressed
to the party as set forth below or (b) the receiving party delivers a written
confirmation of receipt for such notice by any other method permitted under this
paragraph; and further provided that any notice given by facsimile received
after 5:00 p.m. (recipient's time) or on a non-business day shall be deemed
received on the next business day; (iii) five (5) business days after deposit in
the United States mail, certified, return receipt requested, postage prepaid,
and addressed to the party as set forth below; or (iv) the next business day
after deposit with an international overnight delivery service, postage prepaid,
addressed to the party as set forth below with next business day delivery
guaranteed; provided that the sending party receives confirmation of delivery
from the delivery service provider.

5.3  No Rights as Shareholder; Limitation of Liability. This Warrant shall not
entitle the Holder to any of the rights of a shareholder of the Company except
upon exercise in accordance with the terms hereof. No provision hereof, in the
absence of affirmative action by the Holder to purchase shares of Common Stock,
and no mere enumeration herein of the rights or privileges of the Holder, shall
give rise to any liability of the Holder for the Warrant Price hereunder or as a
shareholder of the Company, whether such liability is asserted by the Company or
by creditors of the Company.

5.4  Governing Law. This Warrant shall be governed by and construed in
accordance with the laws of the State of Minnesota as applied to agreements
among Minnesota residents made and to be performed entirely within the State of
Minnesota, without giving effect to the conflict of law principles thereof.

5.5  Binding Effect on Successors. This Warrant shall be binding upon any
corporation succeeding the Company by merger, consolidation or acquisition of
all or substantially all of the Company's assets and/or securities; provided,
that for purposes of this Section 5.5, a sale of the Company's intermittent
blood testing business shall not be deemed a sale of all or substantially all of
the Company's assets. All of the obligations of the Company relating to the
Shares issuable upon the exercise of this Warrant shall survive the exercise and
termination of this Warrant. All of the covenants and agreements of the Company
shall inure to the benefit of the successors and assigns of the Holder.

5.6  Waiver, Amendments and Headings. This Warrant and any provision hereof may
be changed, waived, discharged or terminated only by an instrument in writing
signed by both parties (either generally or in a particular instance and either
retroactively or prospectively). The headings in this Warrant are for purposes
of reference only and shall not affect the meaning or construction of any of the
provisions hereof.

                                                                          Page 3

<PAGE>

--------------------------------------------------------------------------------
                        WARRANT TO PURCHASE COMMON STOCK
--------------------------------------------------------------------------------

IN WITNESS WHEREOF, the Company has caused this Warrant to be signed by its duly
authorized officer this ___ day of January, 2004.

COMPANY:
                                        DIAMETRICS MEDICAL, INC.


                                        By
                                           -------------------------------------

                                        Print Name:
                                                    ----------------------------

                                        Title:
                                               ---------------------------------

                                                                          Page 4

<PAGE>

                                   SCHEDULE A

                           FORM OF NOTICE OF EXERCISE

                [To be signed only upon exercise of the Warrant]

                     TO BE EXECUTED BY THE REGISTERED HOLDER
                         TO EXERCISE THE WITHIN WARRANT

The undersigned hereby elects to purchase _______ shares of Common Stock (the
"Shares") of Diametrics Medical, Inc. under the Warrant to Purchase Common Stock
dated _________, which the undersigned is entitled to purchase pursuant to the
terms of such Warrant, and [check one]:

[ ]  Cash Exercise. The undersigned has delivered $_______, the aggregate
     Warrant Price for _____ Shares purchased herewith, in full in cash or by
     certified or official bank check or wire transfer;

[ ]  Net Exercise. In exchange for the issuance of _______ Shares, the
     undersigned hereby agrees to surrender the right to purchase _______ shares
     of Common Stock pursuant to the net exercise provisions set forth in
     Section 1.2 of the Warrant.

     Please issue a certificate or certificates representing such shares of
Common Stock in the name of the undersigned or in such other name as is
specified below and in the denominations as is set forth below:

     ----------------------------------------------------------------------
     [Type Name of Holder as it should appear on the stock certificate]

     ----------------------------------------------------------------------
     [Requested Denominations - if no denomination is specified, a single
     certificate will be issued]

     The initial address of such Holder to be entered on the books of Company
     shall be:

     --------------------------------------------
     --------------------------------------------
     --------------------------------------------

     The undersigned hereby represents and warrants that the undersigned is
acquiring such shares for his own account for investment purposes only, and not
for resale or with a view to distribution of such shares or any part thereof.


                                        By:
                                           -------------------------------------

                                        Print Name:
                                                   -----------------------------

                                        Title:
                                              ----------------------------------

                                        Dated:
                                              ----------------------------------

<PAGE>

                               FORM OF ASSIGNMENT
                                    (ENTIRE)

               [To be signed only upon transfer of entire Warrant]

                     TO BE EXECUTED BY THE REGISTERED HOLDER
                         TO TRANSFER THE WITHIN WARRANT

FOR VALUE RECEIVED ___________________________ hereby sells, assigns and
transfers unto _____________________________ all rights of the undersigned
under and pursuant to the within Warrant, and the undersigned does hereby
irrevocably constitute and appoint _____________________ Attorney to transfer
the said Warrant on the books of Diametrics Medical, Inc., with full power of
substitution.


----------------------------------------
[Type Name of Holder]


By:
    ------------------------------------
Title:
       ---------------------------------

Dated:
       ---------------------------------

NOTICE

The signature to the foregoing Assignment must correspond exactly to the name as
written upon the face of the within Warrant, without alteration or enlargement
or any change whatsoever.

<PAGE>

                               FORM OF ASSIGNMENT
                                    (PARTIAL)

              [To be signed only upon partial transfer of Warrant]

                     TO BE EXECUTED BY THE REGISTERED HOLDER
                         TO TRANSFER THE WITHIN WARRANT

FOR VALUE RECEIVED ___________________________ hereby sells, assigns and
transfers unto ____________________________ (i) the rights of the undersigned to
purchase ____________________ shares of Common Stock under and pursuant to the
within Warrant, and (ii) on a non-exclusive basis, all other rights of the
undersigned under and pursuant to the within Warrant, it being understood that
the undersigned shall retain, severally (and not jointly) with the transferee(s)
named herein, all rights assigned on such non-exclusive basis. The undersigned
does hereby irrevocably constitute and appoint __________________________
Attorney to transfer the said Warrant on the books of Diametrics Medical, Inc.,
with full power of substitution.


----------------------------------------
[Type Name of Holder]


By:
    ------------------------------------
Title:
       ---------------------------------

Dated:
       ---------------------------------

NOTICE

The signature to the foregoing Assignment must correspond exactly to the name as
written upon the face of the within Warrant, without alteration or enlargement
or any change whatsoever.