Medicare Part D is prescription drug coverage. Medicare Part D plans (PDP) help pay for medications prescribed by a doctor. Part D plans are offered by private insurance companies approved by Medicare. The types of drugs covered is decided by the U.S. government. Beyond that list, every Medicare Part D plan covers a different set of drugs. When choosing a Part D plan, you need to make sure it covers the drugs you take. Most Medicare Advantage (Part C) plans already include Part D prescription drug coverage, combined into a single plan with hospital and medical. Another option is to have a separate Part D plan in addition to Original Medicare, a Medicare Supplement Insurance plan, or a Private Fee-For-Service plan.