LANTHEUS HOLDINGS, INC.

                               POWER OF ATTORNEY

Know all by these presents, that the undersigned hereby constitutes and appoints
each of the President, Treasurer, each Assistant Treasurer, Secretary and each
Assistant Secretary of Lantheus Holdings, Inc. (the "Company"), acting singly or
together and with full power of substitution, as the undersigned's true and
lawful attorney-in-fact with full power and authority to act in the name of and
for and on behalf of the undersigned to:

     (1)   prepare, execute in the undersigned's name and on the undersigned's
           behalf, and submit to the U.S. Securities and Exchange Commission
           (the "SEC") a Form ID, including amendments thereto, and any other
           documents necessary or appropriate to obtain codes and passwords
           enabling the undersigned to make electronic filings with the SEC of
           reports required by Section 16(a) of the Securities Exchange Act of
           1934 or any rule or regulation of the SEC;

     (2)   execute for and on behalf of the undersigned, in the undersigned's
           capacity as an officer and/or director of Company, Forms 3, 4 and 5
           in accordance with Section 16(a) of the Securities Exchange Act of
           1934 and the rules thereunder;

     (3)   do and perform any and all acts for and on behalf of the undersigned
           which may be necessary or desirable to obtain and maintain the
           undersigned's filings codes, complete and execute any such Form 3, 4
           or 5, complete and execute any amendment or amendments thereto, and
           timely file such form with the SEC and any stock exchange or similar
           authority; and

     (4)   take any other action of any type whatsoever in connection with the
           foregoing which, in the opinion of such attorney-in-fact, may be of
           benefit to, in the best interest of, or legally required by or of,
           the undersigned, it being understood that the documents executed by
           such attorney-in-fact on behalf of the undersigned pursuant to this
           Power of Attorney shall be in such form and shall contain such terms
           and conditions as such attorney-in- fact may approve in such
           attorney-in-fact's discretion.

The undersigned hereby grants to each such attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all that such attorney-in-fact, or such
attorney-in-fact's substitute or substitutes, shall lawfully do or cause to be
done by virtue of this power of attorney and the rights and powers herein
granted.  The undersigned acknowledges that the foregoing attorneys-in-fact, in
serving in such capacity at the request of the undersigned, are not assuming,
nor is the Company assuming, any of the undersigned's responsibilities to comply
with Section 16 of the Securities Exchange Act of 1934.

This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4 and 5 with respect to the
undersigned's holdings of, and transactions in, securities issued by the
Company, unless earlier revoked by the undersigned in a signed writing delivered
to the foregoing attorneys-in-fact.

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IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of the date written below.

                                 /s/ Robert J. Marshall, Jr.
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                                         Signature

                                 Robert J. Marshall, Jr.
                                 -----------------------------------
                                         Print Name

                                 9/27/18
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                                         Date