<PAGE>

     EXHIBIT 4.14

     THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE
SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES ACT"), OR ANY STATE
SECURITIES LAWS.  NO SALE, TRANSFER, PLEDGE OR OTHER DISPOSITION OF THIS WARRANT
OR THE SHARES PURCHASABLE HEREUNDER SHALL BE MADE EXCEPT PURSUANT TO
REGISTRATION UNDER THE SECURITIES ACT, AND APPLICABLE STATE SECURITIES LAWS, OR
PURSUANT TO AN EXEMPTION THEREFROM UNDER SUCH ACT AND SUCH STATE LAWS AND THE
RESPECTIVE RULES AN REGULATIONS THEREUNDER.
                                          
                    --------------------------------------------
                                          
                        WARRANT TO PURCHASE COMMON STOCK OF
                                          
                                   SERACARE, INC.
                                          
                    --------------------------------------------
                                          
                               Exercisable as of the
                                          
                                 Commencement Date
                                          
                                 (as defined below)
                                          
                                     Void After
                                          
                                the Expiration Date
                                          
                                 (as defined below)
     

     1

          THIS CERTIFIES that, for value received, Brown Brothers Harriman & 
Co., or registered assigns, is entitled, subject to the terms and conditions 
set forth in this Warrant, to purchase from SERACARE, INC., a Delaware 
corporation (the "Company"), subject to adjustment as provided in paragraph 3 
of this Warrant, 13,793 fully paid and nonassessable shares of Common Stock, 
par value $.001 per share, of the Company (the "Common Stock"), at any time 
commencing on the date hereof (the "Commencement Date") and continuing up to 
5:00 p.m. New York time on the fifth anniversary of the date hereof (the 
"Expiration Date"), at a price of $.01 per share (the "Exercise Price").



                                      21
<PAGE>

     This Warrant is subject to the following provisions:

     SECTION 1.     EXERCISE OF WARRANT

     This Warrant may be exercised by the holder hereof, in whole or in part 
(but not as to a fractional share), by the presentation and surrender of this 
Warrant with the form of election to purchase attached hereto as EXHIBIT A, 
properly completed and executed by the holder by certified mail, by overnight 
courier, in person or by a legal representative or attorney duly authorized 
to do so in writing, at the principal office of the Company (or at such other 
address as the Company may designate by notice in writing to the holder 
hereof at the address of such holder appearing on the books of the Company), 
and upon payment to the Company of an amount equal to the exercise price 
multiplied by the number of shares being purchased pursuant to such exercise, 
payable by payment to the Company in cash, by certified check or by wire 
transfer.  

     The shares of Common Stock so purchased pursuant to the preceding 
paragraph shall be deemed to be issued to the holder hereof as the record 
owner of such shares as of the close of business on the date on which this 
Warrant shall have been surrendered and payment made for such shares.  
Certificates for the shares of Common Stock so purchased shall be delivered 
or mailed to the holder promptly after this Warrant shall have been so 
exercised, and, unless this Warrant has expired or has been exercised in 
full, a new Warrant identical in form but representing the number of shares 
of Common Stock with respect to which this Warrant shall not then have been 
exercised shall also be issued to the holder hereof at the expense of the 
Company.

     The Company shall pay all documentary, stamp or other transactional 
taxes attributable to the issuance or delivery of shares of capital stock of 
the Company upon exercise of this Warrant; PROVIDED, HOWEVER, that the 
Company shall not be required to pay any taxes which may be payable in 
respect of any transfer involved in the issuance or delivery of any 
certificate for such shares in a name other than that of the holder of this 
Warrant in respect of which such shares are being issued.

     SECTION 2.     REPLACEMENT.

     This Warrant is exchangeable, upon its surrender by the holder at the 
principal office of the Company, for new Warrants (containing the same terms 
as this Warrant) each representing the right to purchase such number of 
shares of common stock as shall be designated by such holder at the time of 
surrender (but not exceeding in the aggregate the remaining number of shares 
of common stock which may be purchased hereunder).  Upon receipt of evidence 
satisfactory to the Company of the loss, theft, destruction or mutilation of 
this Warrant and upon delivery of indemnity satisfactory to the Company (or, 
in the case of mutilation, upon surrender of this Warrant), the Company will 
issue to the holder a replacement Warrant (containing the same terms as this 
Warrant).  The unsecured undertaking of the original holder of this Warrant 
or any of its assigns shall constitute satisfactory indemnity for purposes of 
this paragraph. As used herein, "Warrant" shall include all new Warrants 
issued in exchange for or replacement of this Warrant.

     SECTION 3.     ADJUSTMENT OF NUMBER OF SHARES.  



                                      22
<PAGE>

     If the number of shares of Common Stock outstanding at any time 
hereafter is increased by a stock dividend payable in shares of Common Stock 
or by a subdivision or split-up of shares of Common Stock, then, following 
the record date fixed for the determination of holders of Common Stock 
entitled to receive such stock dividend, subdivision or split-up, the number 
of shares of Common Stock issuable on exercise of this Warrant shall be 
increased in proportion to such increase in outstanding shares.

     If at any time hereafter the number of shares of Common Stock 
outstanding is decreased by a combination of the outstanding shares of Common 
Stock or a reverse stock-split, following the record date for such 
combination, the number of shares of Common Stock issuable on exercise of 
this Warrant shall be decreased in proportion to such decrease in outstanding 
shares.

     If at any time hereafter any reorganization, reclassification of the 
capital stock of the Company (other than a change in par value or from par 
value to no par value or from no par value to par value or as a result of a 
stock dividend or subdivision, split-up or combination of shares), 
consolidation or merger (including a merger in which the Company is the 
surviving entity), sale or other disposition of all or substantially all of 
the Company's assets or a distribution of property to shareholders (other 
than distributions payable out of earnings or retained earnings) shall occur, 
then this Warrant shall (in lieu of or, in respect of sales of all or 
substantially all assets or distribution of property to shareholders, in 
addition to, being exercisable for shares of Common Stock) after such 
reorganization, reclassification, consolidation or merger be exercisable into 
the kind and number of shares of stock or other securities or property 
(including cash) of the company or of the corporation resulting from such 
consolidation or surviving such merger or to which such properties and assets 
shall have been sold or otherwise disposed of or distributed to which the 
holder of the number of shares of Common Stock deliverable (immediately prior 
to the time of such reorganization, reclassification, consolidation, merger, 
sale or other disposition or distribution) upon exercise of such Warrant 
would have been entitled upon such reorganization, reclassification, 
consolidation, merger, sale or other disposition or distribution.  The 
provisions of this Section shall similarly apply to successive 
reorganizations, reclassifications and other transactions contemplated above.

     All calculations under this Section 3 shall be made to the nearest cent 
($.01) or to the nearest whole share, as the case may be.

     In any case in which the provisions of this Section 3 shall require that 
an adjustment of the number of shares of Common Stock issuable upon exercise 
of this Warrant shall become effective immediately after a record date for an 
event, the Company may, until the occurrence of such event, defer issuing to 
the holder of the Warrant exercised after such record date and before the 
occurrence of such event the additional shares of capital stock issuable upon 
such exercise by reason of the adjustment required by such event over and 
above the shares of capital stock issuable upon exercise before giving effect 
to such adjustment; PROVIDED, HOWEVER, that the Company shall deliver to such 
holder a due bill or other appropriate instrument evidencing such holder's 
right to receive such additional shares upon the occurrence of the event 
requiring such adjustment.

     Whenever the number of shares of Common Stock issuable upon exercise of 
this Warrant shall be adjusted as provided in Section 3, the Company shall 
promptly thereafter file, at its principal office or at such other place as 
may be designated by the Company, a statement, signed by its president or 
chief financial officer and by its treasurer, showing in reasonable detail 
the facts requiring such adjustment and the number of shares of Common Stock 
issuable upon exercise of this Warrant that shall be in effect after such 
adjustment.  The Company shall cause a copy of such statement to be sent by 
first-class, certified 


                                      23
<PAGE>

mail, return receipt requested, postage prepaid, to each holder of this 
Warrant at such holder's address appearing in the Company's records. 

     The Company will not, by amendment of its Articles of Incorporation or 
By-laws or through any reorganization, transfer of assets, reclassification, 
merger, dissolution, issue or sale of securities or otherwise, avoid or seek 
to avoid the observance or performance of any of the terms to be observed or 
performed by the Company hereunder but will at all times in good faith assist 
in the carrying of all the provisions hereof and in the taking of all such 
actions as may be necessary or appropriate in order to protect the rights of 
the holders of this Warrant against impairment.

     SECTION 4.     FRACTIONAL SHARES.

     No fractional shares shall be issued upon exercise of this Warrant.  In 
the case of this Warrant being exercised in part only, the Company shall, 
upon such exercise, execute and deliver to the holder thereof, at the expense 
of the Company, a new Warrant or Warrants equal to the unexercised portion of 
such Warrant.  Instead of issuing any fractional shares of Common Stock that 
would otherwise be issuable upon exercise of this Warrant, the Company shall 
round off to the nearest whole number of shares of Common Stock.

     SECTION 5.     OBLIGATIONS OF THE COMPANY.

     The Company will at all times reserve, free from any preemptive rights, 
and keep available out of its authorized Common Stock, solely for the purpose 
of issue upon the exercise of Warrants as herein provided, such number of 
shares of Common Stock as shall then be issuable upon the exercise of all 
outstanding Warrants.  The Company covenants and agrees that all shares of 
Common Stock which shall be so issuable will, upon issuance, be duly 
authorized and issued, fully paid and nonassessable.  The Company will not 
take any action which results in any adjustment of the number of shares of 
Common Stock issuable upon exercise of this Warrant if the total number of 
shares of Common Stock issuable after such action upon exercise of this 
Warrant would (a) exceed the total number of shares of Common Stock then 
authorized by the Company's Articles of Incorporation in effect at such time 
or (b) would conflict with, or result in any violation of, or require the 
consent or approval (unless the same shall be obtained) of any court or 
administrative or governmental body pursuant to, or result in a breach of the 
terms, conditions, or provisions of, or constitute a default under, the 
Articles of  Incorporation or By-laws of the Company or any agreement or 
instrument to which the Company is then subject.  The Company will take all 
such action as may be necessary to assure that all such shares of Common 
Stock may be so issued without violation of any applicable requirements of 
any exchange upon which the Common Stock of the Company may be listed or in 
respect of which the Common Stock has qualified for unlisted trading 
privileges.

     The Company will not close its books against the issuance or transfer of 
any shares of Common Stock issuable upon exercise of this Warrant.

     SECTION 6.     TRANSFERABILITY.  

     This Warrant and all rights hereunder are transferable, in whole or in 
part, without charge to the holder, upon surrender of this Warrant with an 
executed Assignment in the form annexed hereto as EXHIBIT B, properly 
executed by the holder hereof and the assignee.



                                      24
<PAGE>

     If this Warrant, or any part hereof, is transferred to another holder 
and such holder shall have designated in writing the address to which 
communications with respect to this Warrant shall be mailed, all notices, 
certificates, requests, statements and other documents required to be 
delivered to the transferring holder by reason for the holding of this 
Warrant shall also be delivered to such holder.

     SECTION 7.     "PIGGYBACK" REGISTRATION RIGHTS.  

     (a)  Subject to Sections 7(b) through 7(d) below, if the Company shall 
determine to proceed with the preparation and filing of a registration 
statement under the Securities Act of 1933, as amended, in connection with 
the proposed offer and sale of any of its securities by it or any of its 
security holders, the Company will give written notice of its determination 
to the holder of this Warrant.  Upon the written request from the holder of 
this Warrant, within twenty (20) days after receipt of any such notice from 
the Company (and receipt by the Company of any information from the holder of 
this Warrant which is required to be included in a registration statement), 
the Company will, except as provided in this Section 7 and at the Company's 
expense, cause all shares of the Company's common stock issuable upon the 
exercise of this Warrant to be included in such registration statement, all 
to the extent requisite to permit the sale or other disposition by the 
prospective seller or sellers of the securities to be so registered; 
PROVIDED, HOWEVER, that nothing herein shall prevent the Company from, at any 
time, abandoning or delaying any registration. If any registration shall be 
underwritten in whole or in part, the Company may require that the securities 
requested for inclusion pursuant to this section be included in the 
underwriting on the same terms and conditions as the securities otherwise 
being sold through the underwriters.  

     (b)  Notwithstanding the foregoing, if the managing underwriter 
determines and advises in writing that the inclusion of the shares of the 
Company's common stock issuable upon the exercise of this Warrant proposed to 
be included in the underwritten public offering would interfere with the 
successful marketing of such offering, then the number of such shares that 
the managing underwriter believes may be sold in such underwritten public 
offering shall be allocated for inclusion in any registration statement in 
the following order of priority: (i) the securities being offered by the 
Company; (ii) the securities being offered by the Investors (as such term is 
defined in Section 7(c) below); (iii) the securities being offered by the 
Holders (as such term is defined in that certain Registration Rights 
Agreement dated February 13, 1998 by and between Sutro & Co. Incorporated, a 
Delaware corporation, or its permitted assigns, and the Company); (iv) the 
securities being sought to be registered by the holder of this Warrant, on a 
PRO RATA basis based upon the number of securities sought to be registered by 
such holder and the number of securities sought to be registered by all 
persons other than those identified in clauses (i) through (iii) above.

          (c)  Notwithstanding the provisions of Section 7(a), the holder of 
this Warrant shall have no rights to registration or to otherwise participate 
in any underwritten public offering of the Company's common stock effected 
pursuant to Section 2.1 of that certain Registration Rights Agreement (the 
"Senior Agreement") dated as of February 13, 1998 by and among the Company 
and the investors named therein (the "Investors") unless: (i) the managing 
underwriter of such offering shall have advised each holder of Registerable 
Securities (as such term is defined in the Senior Agreement) to be covered by 
the registration statement that the inclusion of the securities registerable 
hereunder would not, in such underwriters reasonable judgement, adversely 
effect the marketing or the selling price of the Registerable Securities to 
be covered by such registration statement; and (ii) the holders of a majority 
of the Registerable Securities to be covered by such registration statement 
shall have consented in writing to the inclusion of the securities 
registerable hereunder.



                                      25
<PAGE>

          (d)  The rights granted to the holder of the Warrant under this 
Section 7 shall terminate at such time as the shares of Common Stock issued 
pursuant to the exercise of this Warrant become freely transferable by the 
holder of such shares pursuant to Rule 144 under the Securities Act of 1933, 
as amended.

     SECTION 8.  GOVERNING LAW.

     This Warrant shall be construed and enforced in accordance with the laws 
of the State of Delaware without regard to principles of conflicts of law or 
choice of law.

     SECTION 9.     NO VOTING RIGHTS; LIMITATIONS OF LIABILITY.

     This Warrant shall not entitle the holder hereof to any voting rights or 
other rights as a stockholder of the Company.  No provision hereof, in the 
absence of affirmative action by the holder hereof to exercise this Warrant, 
and no enumeration herein of the rights or privileges of such holder shall 
give rise to any liability of such holder for the exercise price of the 
shares acquirable by exercise hereof or as a stockholder of the Company.

     SECTION 10.  NOTICES.  

     Except as otherwise expressly provided herein, all notices and 
deliveries referred to in this Warrant shall be in writing, shall be 
delivered personally, sent by registered or certified mail, return receipt 
requested and postage prepaid or sent via nationally recognized overnight 
courier or via facsimile, and shall be deemed to have been given when so 
delivered (or when received, if delivered by any other method) if sent (i) to 
the Company, at its principal executive offices and (ii) to the holder of 
this Warrant, at such holder's address as it appears in the records of the 
Company (unless otherwise indicated by any such holder).

     SECTION 11.  AMENDMENT AND WAIVER.

     Except as otherwise provided herein, the provisions of the Warrants may 
be amended and the Company may take any action herein prohibited, or omit to 
perform any act herein required to be performed by it, only if the Company 
has obtained the prior written consent of the holder of this Warrant.
                                          
                             [INTENTIONALLY LEFT BLANK]



                                      26
<PAGE>

     IN WITNESS WHEREOF, the Company has caused this Warrant to be signed by 
its duly authorized officer on this 24th day of April, 1998.
     

     SERACARE, INC.
     
     

     By: /s/ Barry D. Plost                            
        -------------------               ------------------------

          Barry D. Plost

          Chairman and Chief Executive Officer




                                      27
<PAGE>

                                                                       EXHIBIT A
                                          
                            FORM OF ELECTION TO PURCHASE
                                          
                                   SERACARE, INC.

     The undersigned holder of this Warrant (1) hereby irrevocably elects to
exercise the right to purchase hereunder ___ fully paid shares of the Common
Stock of SERACARE, INC., (2) makes payment in full of the purchase price of such
shares, (3) requests that certificates for such shares be issued in the name of
________________, and (4) if said number of shares shall not be all the shares
the holder is entitled to purchase under this Warrant, requests that a new
Warrant for the unexercised and unexpired portion of this Warrant be issued.
     

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

     Dated:               , 199
           ---------------     --
                                 


                                      28
<PAGE>

                                                                       EXHIBIT B

                                     ASSIGNMENT

          FOR VALUE RECEIVED, __________________________ hereby sells, 
assigns and transfers all of the rights of the undersigned under the attached 
Warrant with respect to the number of the shares covered thereby set forth 
below, unto:
     


      Name of Assignee              Address                 No. of Shares
      ----------------              -------                 -------------
                                                           





     

     Dated:                         Signature 
     ----------------------------   
                                    Witness
                                            -------------------------------

          Each assignee of the Warrant hereby acknowledges and agrees that 
this Warrant and the securities into which the Warrant may be exercised have 
not been registered under the Securities Act of 1933, as amended (the 
"Securities Act"), or any state securities laws and that no sale, transfer, 
pledge or other disposition of this Warrant or the shares purchasable 
hereunder shall be made except pursuant to registration under the Securities 
Act and any applicable state securities laws or pursuant to an exemption 
therefrom.



                                      29
<PAGE>

     Dated:
                                   -------------------------------------
                                   Signature of Assignee

     Dated:
                                   -------------------------------------
                                   Signature of Assignee



                                      30