A stand-alone drug plan offered by insurers and other private companies to beneficiaries that receive their Medicare Part A and/or B benefits through the Original Medicare Plan. It includes Medicare Private Fee-for-Service Plans that do not offer prescription drug coverage and Medicare Cost Plans offering Medicare prescription drug coverage. The plan was enacted as the Medicare Prescription Drug, Improvement and Modernization Act of 2003 with coverage beginning January 1, 2006.

Medicare Prescription Drug Improvement and Modernization Act of 2003, PL 108-173.

Synonyms: PL 108 173 PL 108-173 Part D, Medicare Medicare Part D