<PAGE>
                                                                     Exhibit 4.4

THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES
ACT OF 1933, AS AMENDED (THE "ACT"), OR UNDER THE SECURITIES LAWS OF CERTAIN
STATES. THESE SECURITIES ARE SUBJECT TO RESTRICTIONS ON TRANSFERABILITY AND
RESALE AND MAY NOT BE TRANSFERRED OR RESOLD EXCEPT AS PERMITTED UNDER THE ACT
AND THE APPLICABLE STATE SECURITIES LAWS. PURSUANT TO REGISTRATION OR EXEMPTION
THEREFROM. INVESTORS SHOULD BE AWARE THAT THEY MAY BE REQUIRED TO BEAR THE
FINANCIAL RISKS OF THIS INVESTMENT FOR AN INDEFINITE PERIOD OF TIME. THE ISSUER
OF THESE SECURITIES MAY REQUIRE AN OPINION OF COUNSEL IN FORM AND SUBSTANCE
SATISFACTORY TO THE ISSUER TO THE EFFECT THAT ANY PROPOSED TRANSFER OR RESALE IS
IN COMPLIANCE WITH THE ACT AND ANY APPLICABLE STATE SECURITIES LAWS.

              VOID AFTER 5:00 P.M. CALIFORNIA TIME ON MARCH 2, 2005

                   WARRANT TO PURCHASE SHARES OF COMMON STOCK
                                       OF
                         CALYPTE BIOMEDICAL CORPORATION

                 (BRIDGE LOAN WARRANT TO TRILOBITE LAKES CORP.)

                          ISSUANCE DATE: MARCH 2, 2000
TRILOBITE LAKES CORP., a Delaware corporation, as the original holder hereof,
and any person to whom the interest in this Warrant is lawfully transferred (the
original holder hereof and such transferees referred to hereinafter as the
"HOLDER"), is entitled to purchase one hundred thousand (100,000) shares (as
adjusted pursuant to Section 2 hereof) of fully paid and nonassessable Common
Stock (the "SHARES") of CALYPTE BIOMEDICAL CORPORATION, a Delaware corporation
(the "COMPANY"). This Warrant is being issued to the Holder in connection with,
and simultaneously with, the loan by the Holder to the Company of up to a total
of one million dollars ($1,000,000.00) pursuant to a Bridge Loan Agreement dated
as of the Issuance Date hereof, to which the Company, as borrower thereunder,
and the Holder, as lender thereunder, are parties (the "BRIDGE LOAN AGREEMENT").

         1.       EXERCISE OF WARRANT.

                  (a)      EXERCISE PRICE; AGGREGATE EXERCISE PRICE. The
Exercise Price at which this Warrant may be exercised will be $3.62 per share,
which exercise price per share is one hundred thirty percent (130%) of the
average closing price of the Company's Common Stock on the five (5) days prior
to, and including, the Issuance Date, as such Exercise Price may be adjusted
from time to time pursuant to Section 2 hereof. The Aggregate Exercise Price
will be the amount resulting from multiplying the Exercise Price times the
number of Shares purchased upon exercise hereof.

                  (b)      EXERCISE PERIOD. This Warrant will become
exerciseable from and after the Issuance Date. To the extent this Warrant is not
previously exercised pursuant to the terms hereof, this Warrant will expire and
be void upon and after 5:00 p.m., California time, on March 2, 2005.

                  (c)      METHOD OF EXERCISE; PAYMENT. The purchase right
represented by this Warrant may be exercised by the Holder, in whole or in part,
for up to the total number of Shares remaining available to exercise by the
delivery at the principal office of the Company of: (i) this Warrant, and (ii) a
duly executed Notice of Exercise (the "EXERCISE NOTICE") in the form attached
hereto as ANNEX I-A, if when this Warrant is exercised the shares issuable upon
such exercise are not registered for public resale under the Act, or in the form
of ANNEX I-B if when this Warrant is exercised the shares issuable upon such
exercise are registered for public resale under the Act, and (iii) the payment
to the Company of an amount in each case equal to the then-applicable Exercise
Price per share multiplied by the number of Shares then being purchased, by: (A)

<PAGE>

check made payable to the Company drawn on a United States bank and for United
States funds, and/or (B) delivery to the Company of evidence of cancellation of
indebtedness of the Company to such Holder, and/or (C) any combination thereof.

                  (d)      NET ISSUE ELECTION. In lieu of exercising this
Warrant pursuant to Section 1(c) hereof, the Holder may elect to receive,
without the payment by the Holder of any additional consideration, shares of
Common Stock of the Company equal to the value of this Warrant or any portion
hereof (the "NET EXERCISE") by the surrender of this Warrant or such portion
hereof to the Company at the principal office of the Company together with a
completed Exercise Notice with the net exercise election therein properly
initialed. Thereupon, the Company will issue to the Holder such number of fully
paid and nonassessable shares of Common Stock of the Company as is computed
using the following formula:

             X = Y (A-B)
                 -------
                    A

             where:

             X = The number of Shares to be issued to the Holder pursuant to
                 this Section 1(d).

             Y = The number of Shares covered by this Warrant in respect of
                 which the Net Exercise election is made pursuant to this
                 Section 1(d).

             A = The average of the closing prices of one share of Common
                 Stock of the Company for the five (5) days immediately
                 preceding, and not including, the date on which this Warrant
                 is so exercised, on which five days the Company's Common
                 Stock was traded on Nasdaq or such other stock exchange upon
                 which its Common Stock is then traded.

             B = The Exercise Price in effect under this Warrant at the time
                 the Net Exercise election is made pursuant to this Section
                 1(d).

         To the extent legally required, the Holder will pay in cash the par
value of any shares purchased by such Net Exercise.

                  (e)      ISSUANCE OF NEW WARRANT. In the event of any exercise
of the purchase right represented by this Warrant, certificates for the Shares
so purchased will be delivered to the Holder within ten (10) business days after
receipt of such payment and, unless this Warrant has been fully exercised or has
expired, a new Warrant representing the portion of the Shares, if any, with
respect to which this Warrant will not then have been exercised will also be
issued to the Holder within such ten (10) business day period, a "BUSINESS DAY"
being defined for purposes hereof as a day when U.S. national banks are open for
business.

         2.       ADJUSTMENTS TO WARRANT. The number and kind of securities
purchasable upon the exercise of this Warrant, and the Exercise Price, will be
subject to adjustment from time to time upon the occurrence of certain events,
as follows:

                  (a)      RECLASSIFICATION, REORGANIZATION, CONSOLIDATION OR
MERGER. In case of any reclassification of the Company's Common Stock, or any
reorganization, consolidation or merger of the Company with or into another
corporation (other than a merger or reorganization with respect to which the
Company is the continuing corporation and which does not result in any
reclassification of the Company's Common Stock), the Company, or such successor
corporation, as the case may be, will execute and deliver


                                      -2-
<PAGE>

to Holder a new warrant in substitution for this Warrant which will provide that
the Holder will have the right to exercise such new warrant and upon such
exercise to receive, in lieu of each share of Common Stock previously issuable
upon exercise of this Warrant, the number and kind of securities, money and
property receivable upon such reclassification, reorganization, consolidation or
merger by a holder of shares of Common Stock of the Company for each share of
Common Stock otherwise issuable hereunder. Such new Warrant will provide for
adjustments which will be as nearly equivalents as may be practicable to the
adjustments provided for in this Section 2 including, without limitation,
adjustments to the Exercise Price and to the number of shares issuable upon
exercise of this Warrant. The provisions of this Section 2(a) will similarly
apply to successive reclassifications, reorganizations, consolidations or
mergers.

                  (b)      SPLIT, SUBDIVISION OR COMBINATION OF SHARES. If the
Company at any time while this Warrant remains outstanding and unexpired splits,
subdivides or combines its Common Stock, the number of shares for which this
Warrant is exerciseable will thereafter be adjusted to take account of such
split, subdivision or combination, and the Exercise Price will be
proportionately decreased in the case of a split or subdivision or
proportionately increased in the case of a combination. Any adjustment under
this Section 2(b) will become effective when the split, subdivision or
combination becomes effective.

                  (c)      STOCK DIVIDENDS. If the Company at any time while
this Warrant remains outstanding and unexpired pays a dividend with respect to
its Common Stock payable in shares of its Common Stock, securities convertible
into or exchangeable for its Common Stock ("CONVERTIBLE SECURITIES"), or options
to purchase Convertible Securities or its Common Stock, as applicable
("OPTIONS"), the Exercise Price will be adjusted from and after the date of
determination of the stockholders entitled to receive such dividend or
distribution, to that price determined by multiplying the Exercise Price in
effect immediately prior to such date of determination by a fraction (i) the
numerator of which will be the total number of shares of Common Stock
outstanding immediately prior to such dividend or distribution, and (ii) the
denominator of which will be the total number of shares of Common Stock
outstanding immediately after such dividend or distribution (including shares of
Common Stock issuable upon exercise, conversion or exchange of any Options or
Convertible Securities issued as such dividend or distribution), and the number
of shares for which this Warrant will be exerciseable will also be
proportionately adjusted. If the Options or Convertible Securities issued as
such dividend or distributions by their terms provide, with the passage of time
or otherwise, for any decrease in the consideration payable to the Company, or
any increase in the number of shares issuable upon exercise, conversion or
exchange thereof (by change of rate or otherwise), the Exercise Price will, upon
any such decrease or increase becoming effective, be reduced or increased to
reflect such decrease or increase as if such decrease or increase became
effective immediately prior to the issuance of the Options or Convertible
Securities as the dividend or distribution, and the number of shares for which
this Warrant is exerciseable will also be proportionately adjusted. Any
adjustment under this Section 2(c) will become effective on the record date or,
if there is no record date, on the date of issuance.

                  (d)      ADJUSTMENT OF NUMBER OF SHARES. Upon each adjustment
in the Exercise Price pursuant to this Section 2, the number of shares issuable
upon exercise of this Warrant will be adjusted to the number obtained by
dividing the then outstanding Aggregate Exercise Price by the Exercise Price
immediately after such adjustment.

         3.       LEGENDS; TRANSFERABILITY OF WARRANT; REGISTRATION ON FORM S-3;
                  RULE 144.

                  (a)      LEGENDS. Any certificate for shares issued upon
exercise hereof prior to the registration of the shares for public resale, as
set forth in Section 3(c) hereof, will be imprinted with a legend in
substantially the form set forth in the Exercise Notice.


                                      -3-
<PAGE>

                  (b)      TRANSFERABILITY OF WARRANT. Subject to compliance
with applicable securities laws, this Warrant may be transferred in the same
manner as a negotiable instrument transferable by endorsement and delivery, by
execution and delivery of a completed Assignment Form attached hereto as Annex
II.

                  (c)      REGISTRATION ON FORM S-3; RULE 144. The resale of
shares issued upon exercise hereof will be in compliance with all applicable
securities laws. Reference is made to the provisions of Section 3(c) of the
Bridge Loan Agreement with respect thereto.

         4.       MISCELLANEOUS. No fractional shares will be issued in
connection with any exercise hereunder, but in lieu of such fractional shares
the Company will make a cash payment therefor upon the basis of the Exercise
Price then in effect. The terms and provisions of this Warrant will inure to the
benefit of, and be binding upon, the Company and the Holder and their respective
successors and assigns of the Holder and of the Company. This Warrant will be
governed by and construed under the laws of the State of California, without
regard to that body of law pertaining to conflict of laws or choice of law. The
titles of the sections and subsections of this Warrant are for convenience only
and are not to be considered in construing this Warrant.

                         CALYPTE BIOMEDICAL CORPORATION


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

WARRANT ACCEPTED AND AGREED:

TRILOBITE LAKES CORP.

By:
   ------------------------------------
Name:
     ----------------------------------
Title:
      ---------------------------------
Date signed:  March _, 2000


                                      -4-
<PAGE>

                                    ANNEX I-A

                               NOTICE OF EXERCISE

                              (BRIDGE LOAN WARRANT)

                     (USE THIS FORM IF WARRANT IS EXERCISED
              BEFORE SHARES HAVE BEEN REGISTERED FOR PUBLIC RESALE)

                              DATE: ________, _____

Calypte Biomedical Corporation

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

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

                  Re:      COMMON STOCK WARRANT NOTICE OF EXERCISE

Ladies/Gentleman:

         On this date, the undersigned ________________________________________,
as the Holder of, and as defined in, that certain Warrant (the "WARRANT") dated
as of March 2, 2000 from the Company to the original holder of such Warrant,
hereby acquires from CALYPTE BIOMEDICAL CORPORATION, a Delaware corporation (the
"COMPANY"), an aggregate of ________ shares (the "RESTRICTED SECURITIES") of the
Common Stock of the Company by exercise of the Warrant hereby for such number of
shares.

         1.       INVESTMENT INTENT. The undersigned represents and warrants
that:

                  (a)      The Restricted Securities have been acquired by the
undersigned for investment and not with a view to the sale or other distribution
thereof within the meaning of the Securities Act of 1933, as amended (the
"SECURITIES ACT"), and the undersigned has no present intention of selling or
otherwise disposing of all or any portion of the Restricted Securities.

                  (b)      The undersigned has acquired the Restricted
Securities for the undersigned's own account and no one else has any beneficial
ownership in the Restricted Securities.

         2.       RESTRICTIONS ON TRANSFER. The undersigned understands that:

                  (a)      In reliance upon the representations and warranties
set forth herein, the Restricted Securities have not been registered with the
Securities and Exchange Commission (the "SEC"), and accordingly may not be
offered, sold or otherwise transferred except in compliance with the Securities
Act (including any exemptions from registration thereunder);

                  (b)      The undersigned must bear the economic risk of the
undersigned's investment in the Restricted Securities indefinitely unless the
Restricted Securities are registered pursuant to the Securities Act or, in the
opinion of counsel in form and substance satisfactory to the Company, an
exemption from the registration requirement is available;

                  (c)      The undersigned cannot be assured that any exemption
from the registration requirement will be available should the undersigned
desire to transfer the Restricted Securities, and therefore, the undersigned may
not be able to dispose of or otherwise transfer the Restricted Securities, under
the circumstances, in the amounts, or at the time proposed by the undersigned;

<PAGE>

                  (d)      Rule 144 promulgated under the Securities Act, which
provides for certain limited, routine sales of unregistered securities, is not
presently available with respect to the Restricted Securities, and the Company
is under no obligation to furnish the information that might be necessary to
enable the undersigned to sell any of the Restricted Securities under Rule 144;
and

                  (e)      Only the Company may file a registration statement
with the SEC, and unless otherwise required to do so pursuant that certain
Investors' Rights Agreement, as may be amended from time to time, between the
Company and certain security holders of the Company dated of even date with or
after the date of the Warrant: (i) the Company is under no obligation to do so
with respect to the Restricted Securities; nor (ii) does the Company have any
obligation to file any other disclosure statement with the SEC with respect
thereto.

         3.       LEGEND AND STOP-TRANSFER ORDERS. The undersigned understands
that, if required by applicable federal securities laws at the date of issuance
of the Restricted Securities, certificates or other instruments representing any
of the Restricted Securities acquired by the undersigned will bear a legend
substantially similar to the following, in addition to any other legends
required by federal or state laws, or by any contractual agreement binding upon
the undersigned with respect to the Restricted Securities:

         THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE
         SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"), OR UNDER THE SECURITIES
         LAWS OF CERTAIN STATES. THESE SECURITIES ARE SUBJECT TO RESTRICTIONS ON
         TRANSFERABILITY AND RESALE AND MAY NOT BE TRANSFERRED OR RESOLD EXCEPT
         AS PERMITTED UNDER THE ACT AND THE APPLICABLE STATE SECURITIES LAWS,
         PURSUANT TO REGISTRATION OR EXEMPTION THEREFROM. INVESTORS SHOULD BE
         AWARE THAT THEY MAY BE REQUIRED TO BEAR THE FINANCIAL RISKS OF THIS
         INVESTMENT FOR ANY INDEFINITE PERIOD OF TIME. THE ISSUER OF THESE
         SECURITIES MAY REQUIRE AN OPINION OF COUNSEL IN FORM AND SUBSTANCE
         SATISFACTORY TO THE ISSUER TO THE EFFECT THAT ANY PROPOSED TRANSFER OR
         RESALE IS IN COMPLIANCE WITH THE ACT AND ANY APPLICABLE STATE
         SECURITIES LAWS.

         The undersigned agrees that, to ensure and enforce compliance with the
restrictions imposed by applicable law and those referred to in the foregoing
legend, or elsewhere herein, the Company may issue appropriate "stop transfer"
instructions to its transfer agent, if any, with respect to any certificate or
other instrument representing Restricted Securities, or if the Company transfers
its own securities, that it may make appropriate notation to the same effect in
the Company's records.

         4.       REPRESENTATIONS AND WARRANTIES. The undersigned represents and
warrants that:

                  (a)      The undersigned has had access to all information
regarding the Company, its present and prospective business, assets, liabilities
and financial condition that the undersigned considers important to making the
decision to invest in the Restricted Securities. The undersigned has had ample
opportunity to ask questions of and receive answers from the Company's
representatives concerning this investment and to obtain any and all documents
requested in order to supplement or verify any of the information supplied.

                  (b)      The undersigned recognizes that the investment in the
Restricted Securities involves special and substantial risks. The undersigned
recognizes (i) the highly speculative nature of the investment, (ii) the
financial hazards involved, (iii) the lack of liquidity of the Restricted
Securities and the restrictions


                                      -2-
<PAGE>

upon transferability thereof, (iv) the qualifications and backgrounds of the
principals of the Company, and (v) the tax consequences of investment in
Restricted Securities, among other matters.

                  (c)      The undersigned is capable of evaluating the merits
and risks of an investment in the Restricted Securities and is financially
capable of bearing a total loss of this investment.

                  (d)      The undersigned either (i) has a preexisting personal
or business relationship with the Company or its principals or (ii) by reason of
the undersigned's business or financial experience, has the capacity to protect
the undersigned's own interests in connection with this transaction.

                  (e)      The offer and sale of the Restricted Securities was
not accomplished by the publication of any advertisement.

                  (f)      The undersigned's address is:
                                                        ------------------------

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

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

                  (g)      NET EXERCISE ELECTION: If applicable, the undersigned
elects to purchase the Securities by Net Exercise (as defined in the Warrant),
by INITIALING in the following space (please initial ONLY if Net Exercise
chosen): ___________.

PRINTED NAME IF INDIVIDUAL :
                            ----------------------------------------------------

--------------------------------------------
                 Signature

Date signed:  _____________, _________
Address:
        ------------------------------------

        ------------------------------------
Social Security Number:
                       ---------------------

PRINTED NAME IF CORPORATE/PARTNERSHIP/TRUST:

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

By:
   -----------------------------------------
Name:
     ---------------------------------------
Title:
      --------------------------------------
Date signed:  _____________, _________
Address:
        ------------------------------------

--------------------------------------------
Taxpayer Identification Number:
                               -------------


                                      -3-
<PAGE>

                                    ANNEX I-B

                               NOTICE OF EXERCISE

                              (BRIDGE LOAN WARRANT)

                     (USE THIS FORM IF WARRANT IS EXERCISED
              AFTER SHARES HAVE BEEN REGISTERED FOR PUBLIC RESALE)

                              DATE: ________, _____

Calypte Biomedical Corporation

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

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

                  Re:      COMMON STOCK WARRANT NOTICE OF EXERCISE

Ladies/Gentleman:

         On this date, the undersigned ________________________________________,
as the Holder of, and as defined in, that certain Warrant (the "WARRANT") dated
as of March 2, 2000 from the Company to the original holder of such Warrant,
hereby acquires from CALYPTE BIOMEDICAL CORPORATION, a Delaware corporation (the
"COMPANY"), an aggregate of ________ shares (the "SECURITIES") of the Common
Stock of the Company by exercise of the Warrant hereby for such number of
shares.

         NET EXERCISE ELECTION: If applicable, the undersigned elects to
purchase the Securities by Net Exercise (as defined in the Warrant), by
INITIALING in the following space (please initial ONLY if Net Exercise chosen):
___________.

PRINTED NAME IF INDIVIDUAL :
                            ----------------------------------------------------

--------------------------------------------
                Signature
Date signed:  _____________, _________
Address:
        ------------------------------------

--------------------------------------------
Social Security Number:
                       ---------------------

PRINTED NAME IF CORPORATE/PARTNERSHIP/TRUST:

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

By:
   -----------------------------------------
Name:
     ---------------------------------------
Title:
      --------------------------------------
Date signed:  _____________, _________
Address:
        ------------------------------------

--------------------------------------------
Taxpayer Identification Number:
                               -------------

<PAGE>

                                    ANNEX II

                                 ASSIGNMENT FORM

                              (BRIDGE LOAN WARRANT)

                         CALYPTE BIOMEDICAL CORPORATION
                              COMMON STOCK WARRANT

  (To assign the foregoing Warrant, execute this form and supply the required
 information) (Do not use this form to exercise the Warrant to purchase shares.)

FOR VALUE RECEIVED, the foregoing Warrant for Common Stock of CALYPTE BIOMEDICAL
CORPORATION and all rights evidenced thereby are hereby assigned to:

(PLEASE PRINT NAME OF ASSIGNEE)
                                ------------------------------------------------
whose address is (PLEASE PRINT)
                                ------------------------------------------------


Date:___________________, __________

Assigning Holder's Printed Name:
                                ------------------------------------------------
Assigning Holder's SIGNATURE:
                                ------------------------------------------------
Assigning Holder's Address:
                                ------------------------------------------------


NOTE: The signature to this Assignment must correspond with the name as it
appears on the face of the assigned Warrant, without any change. Officers of
corporations and those acting in a fiduciary or other representative capacity
should file with this Assignment proper evidence of authority to assign the
foregoing Warrant.