Lantheus (LNTH) S-8 Registration of securities for employees

Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in this Registration Statement onForm S-8 of our report dated February 20, 2019, relating to the financial statements of Lantheus Holdings, Inc. and its subsidiaries, appearing in the Annual Report onForm 10-K of Lantheus Holdings, Inc. and its subsidiaries for the year ended December 31, 2018.

/s/ Deloitte & Touche LLP

Boston, Massachusetts

July 31, 2019