Not to be confused with Medicare Part D for prescription drug coverage, the Medicare Supplement or Medigap Plan D used to be a fairly popular plan many years ago. And while it is trying to make a comeback due to recent MACRA legislation, availability is still quite limited. Plan D may not be the most robust of the Medicare supplement plans, but it still offers excellent coverage and is generally one of the most cost-effective plans of choice. In fact, Plan D covers most of the same benefits as Plan C, with the exception of only the Part B deductible.