<PAGE>   1
                                                                    EXHIBIT 4.14


                                AMENDMENT NO. 12


        THIS AMENDMENT NO. 12, dated as of June 30, 2001 (the "Amendment")
relating to the Credit Agreement referenced below, by and among NATIONAL MEDICAL
CARE, INC., a Delaware corporation, certain subsidiaries and affiliates party to
the Credit Agreement and identified on the signature pages hereto, and BANK OF
AMERICA, N.A., (formerly known as NationsBank, N.A), as Paying Agent for and on
behalf of the Lenders. Terms used but not otherwise defined shall have the
meanings provided in the Credit Agreement.

                               W I T N E S S E T H

        WHEREAS, a $2.5 billion credit facility has been extended to National
Medical Care, Inc. and certain subsidiaries and affiliates pursuant to the terms
of that Credit Agreement dated as of September 27, 1996 (as amended and
modified, the "Credit Agreement") among National Medical Care, Inc., the other
Borrowers, Guarantors and the Lenders identified therein, and NationsBank, N.A.,
as Paying Agent.

        WHEREAS, the Company has requested the modification of certain covenants
and certain other changes to the Credit Agreement more fully set forth herein;

        WHEREAS, the requested consents and modifications described herein
require the consent of the Required Lenders; and

        WHEREAS, the Required Lenders have consented to the requested
modifications on the terms and conditions set forth herein and have authorized
the Paying Agent to enter into this Amendment on their behalf to give effect to
this Amendment.

        NOW, THEREFORE, IN CONSIDERATION of these premises and other good and
valuable consideration, the receipt and sufficiency of which is hereby
acknowledged, the parties hereto agree as follows:

        1.      The Credit Agreement is amended and modified in the following
respects:

                1.1     Section 8.1 is hereby amended by deleting clause (f)
        therefrom in its entirety and substituting the following clause in its
        place as a new clause (f):

                        (f)     in addition to other Indebtedness permitted by
                this Section 8.1,

                                (A)     other Funded Debt of Holdings and its
                        Foreign Subsidiaries in an aggregate amount not to
                        exceed $200 million (or the approximate Dollar
                        Equivalent thereof on the date on which the amount
                        thereof is fixed, to the extent that any such
                        Indebtedness is issued in Foreign Currency) and

                                (B)     other Funded Debt of Holdings and its
                        Foreign Subsidiaries in an aggregate amount not to
                        exceed $400 million at any time outstanding;

                provided, however that (i) neither the Company nor any of its
                Subsidiaries shall have any obligation with respect to any such
                Funded Debt; (ii) no more than $50 million of the Funded Debt
                permitted by subclause (B) may be incurred, created or assumed
                by


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                Holdings (except as a Guaranty Obligation) and (iii) no more
                than $250 million in aggregate principal amount of Funded Debt
                permitted by subclause (B) may be guaranteed by Holdings.

                1.2     Section 8.1 is hereby further amended by deleting clause
        (j) therefrom in its entirety and inserting the following in its place:

                        (j) [INTENTIONALLY OMITTED];

                1.3     Section 8.4(d) is hereby amended by deleting the
        reference to "$400,000,000" in subclause (B) thereof and inserting a
        reference to "$600 million" in its place.

                1.4     It is hereby understood and agreed that the acquisition
        by Holdings and its Subsidiaries of Everest Healthcare Services
        Corporation on January 5, 2001 shall be deemed to have occurred in
        calendar year 2000 for purposes of Section 8.4(d), as a permitted use of
        the proceeds of the Equity Transactions occurring during 2000, as
        contemplated by Amendment No. 10 to the Credit Agreement.

        2.      The Lenders hereby waive compliance with the provisions of the
Credit Agreement as in effect before the execution and delivery of this
Amendment to the extent, and only to the extent, that any transaction or action
of any member of the Consolidated Group have been consented to hereby or would
have been permitted by the provisions of the Credit Agreement, as amended
hereby.

        3.      The effectiveness of this Amendment is subject to receipt by the
Paying Agent of the following:

                (i)     copies of this Amendment executed by the Company and the
        other members of the Consolidated Group identified on the signature
        pages hereto,

                (ii)    the consent of the Required Lenders; and

                (iii)   an amendment fee in an amount equal to seven and
        one-half basis points (0.075%) of the aggregate amount of Commitments
        held by the Lenders consenting to this Amendment for the ratable benefit
        of such consenting Lenders.

        4.      Except as modified hereby, all of the terms and provisions of
the Credit Agreement (and Exhibits and Schedules) remain in full force and
effect.

        5.      The Credit Parties hereby affirm (i) the representations and
warranties set out in Section 6 of the Credit Agreement are true and correct as
of the date hereof (except those which expressly relate to an earlier period)
and (ii) no Default or Event of Default presently exists.

        6.      The Company agrees to pay all reasonable costs and expenses of
the Paying Agent in connection with the preparation, execution and delivery of
this Amendment, including without limitation the reasonable fees and expenses of
Moore & Van Allen, PLLC.

        7.      This Amendment may be executed in any number of counterparts,
each of which when so executed and delivered shall be deemed an original and its
shall not be necessary in making proof of this Amendment to produce or account
for more than one such counterpart.


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        8.      This Amendment, and the Credit Agreement as amended hereby,
shall be governed by and construed and interpreted in accordance with the laws
of the State of New York.

                  [Remainder of Page Intentionally Left Blank]



                                       3
<PAGE>   4


        IN WITNESS WHEREOF, each of the parties hereto has caused a counterpart
of this Amendment to be duly executed and delivered as of the date first above
written.


BORROWERS:                      NATIONAL MEDICAL CARE, INC.,
                           a Delaware corporation

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

                           FRESENIUS MEDICAL CARE AG

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

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

                           NMC DO BRASIL LTDA.,
                           a Brazil corporation

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

                           NATIONAL MEDICAL CARE OF SPAIN, S.A.,
                           a Spanish corporation

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

                           NATIONAL MEDICAL CARE OF TAIWAN, INC.,
                           a Delaware corporation

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

                           NMC CENTRO MEDICO NACIONAL, LDA.,
                           a Portuguese corporation

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


<PAGE>   5

                           FRESENIUS MEDICAL CARE ARGENTINA, S.A.,
                           as successor by merger to
                           NMC DE ARGENTINA, S.A.,
                           an Argentine corporation

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

                           FRESENIUS USA, INC.,
                           a Massachusetts corporation

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

                           FRESENIUS MEDICAL CARE DEUTSCHLAND GmbH,
                           a German corporation

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

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

                           FRESENIUS MEDICAL CARE GROUPE FRANCE
                           (formerly known as Fresenius Groupe France S.A.),
                           a French corporation

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

                           FRESENIUS MEDICAL CARE HOLDING, S.p.A.,
                           an Italian corporation

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

                           FRESENIUS MEDICAL CARE ESPANA S.A.,
                           a Spanish corporation

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


<PAGE>   6

                           FRESENIUS MEDICAL CARE MAGYAROSZA KfG,
                           a Hungarian corporation

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

                           BIO-MEDICAL APPLICATIONS OF ALABAMA, INC.

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

                           BIO-MEDICAL APPLICATIONS OF FLORIDA, INC.

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

                           BIO-MEDICAL APPLICATIONS OF GEORGIA, INC.

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

                           BIO-MEDICAL APPLICATIONS OF INDIANA, INC.

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

                           BIO-MEDICAL APPLICATIONS OF KENTUCKY, INC.

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

                           BIO-MEDICAL APPLICATIONS OF LOUISIANA, INC.

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



<PAGE>   7


                           BIO-MEDICAL APPLICATIONS OF MARYLAND, INC.

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

                           BIO-MEDICAL APPLICATIONS OF
                             MASSACHUSETTS, INC.

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

                           BIO-MEDICAL APPLICATIONS OF
                             NORTH CAROLINA, INC.

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

                           BIO-MEDICAL APPLICATIONS OF OHIO, INC.

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

                           BIO-MEDICAL APPLICATIONS OF PENNSYLVANIA, INC.

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

                           BIO-MEDICAL APPLICATIONS OF
                             SOUTH CAROLINA, INC.

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

                           BIO-MEDICAL APPLICATIONS OF TEXAS, INC.

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



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                           BIO-MEDICAL APPLICATIONS OF VIRGINIA, INC.

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

                           LIFECHEM, INC.,
                           a Delaware corporation

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

GUARANTORS:                FRESENIUS MEDICAL CARE HOLDINGS, INC.,
                           a New York corporation formerly known as WRG-NY

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

                           NATIONAL MEDICAL CARE, INC.,
                           a Delaware corporation

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

                           BIO-MEDICAL APPLICATIONS MANAGEMENT CO.,
                           INC., a Delaware corporation

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

                           FRESENIUS MEDICAL CARE AG,
                           a German corporation

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

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



<PAGE>   9


                           FRESENIUS USA, INC.,
                           a Massachusetts corporation

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

                           FRESENIUS MEDICAL CARE DEUTSCHLAND
                           GmbH, a German corporation

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

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

                           FRESENIUS MEDICAL CARE GROUPE FRANCE, a
                           French corporation (formerly known as
                           Fresenius Groupe France S.A.)

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

                           FRESENIUS SECURITIES, INC.,
                           a California corporation

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

                           NEOMEDICA, INC.,
                           a Delaware corporation

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

                           FMC FINANCE S.A.,
                           a Luxembourg corporation

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



<PAGE>   10


                           FMC TRUST FINANCE S.a.r.l. LUXEMBOURG,
                           a Luxembourg corporation

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


                           QCI HOLDINGS, INC.,
                           a Delaware corporation

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


                           SRC HOLDINGS, INC.,
                           a Delaware corporation

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



PAYING AGENT:              BANK OF AMERICA, N.A. (formerly known as NationsBank,
                           N.A.), as Paying Agent for and on behalf of the
                           Lenders

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




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                           CONSENT TO AMENDMENT NO. 12


Bank of America, N.A. (formerly known as NationsBank, N.A.),
  as Paying Agent
101 N. Tryon Street, 15th Floor
NC1-001-15-04
Charlotte, North Carolina 28255
Attn:  James D. Young, Agency Services

        Re:     Credit Agreement dated as of September 27, 1996 (as amended and
                modified, the "Credit Agreement") among National Medical Care,
                Inc., the other Borrowers, Guarantors and Lenders identified
                therein and NationsBank, N.A. (now known as Bank of America,
                N.A.), as Paying Agent. Terms used but not otherwise defined
                shall have the meanings provided in the Credit Agreement.

                Amendment No. 12 dated June 30, 2001 (the "Subject Amendment")
                relating to the Credit Agreement

Ladies and Gentlemen:

        This should serve to confirm our receipt of, and consent to, the Subject
Amendment. We hereby authorize and direct you, as Paying Agent for the Lenders,
to enter into the Subject Amendment on our behalf in accordance with the terms
of the Credit Agreement upon your receipt of such consent and direction from the
Required Lenders, and agree that Company and the other Credit Parties may rely
on such authorization.

                                            Sincerely,



                                            -----------------------------
                                                   [Name of Lender]

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