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Medicare Part D -

Prescription Drug Coverage

Medicare Part D, the prescription drug benefit, is the part of Medicare that covers most outpatient prescription drugs. Part D is offered through private companies either as a stand-alone plan, for those enrolled in Original Medicare, or as a set of benefits included with your Medicare Advantage Plan.

Unless you have creditable drug coverage and will enroll during your Special Enrollment Period, you should enroll in Part D when you first get Medicare. If you delay enrollment, you may face gaps in coverage and enrollment penalties that will last the lifetime of your coverage. 

Medicare defines creditable drug coverage as an insurance plan that is expected to pay on average as much as the standard Medicare prescription drug coverage.

Part D Coverage

Each Part D plan has a list of covered drugs, called its formulary. If the drug you need is not on the formulary, you may request an exception, pay out of pocket, or file an appeal.

A drug category is a group of drugs that treat the same symptoms or have similar effects on the body.


All Part D plans must include at least two drugs from most categories and must cover all drugs available in the following categories:

  • HIV/AIDS treatments

  • Antidepressants

  • Antipsychotic medications

  • Anticonvulsive treatments for seizure disorders

  • Immunosuppressant drugs

  • Anticancer drugs (unless covered by Part B)


Part D plans must also cover most vaccines, except for vaccines covered by Part B.


Drugs used to treat weight loss or gain, over-the-counter drugs, and some others are explicitly excluded from Medicare coverage by law.

Note: For certain drugs or under specific circumstances, your drugs may be covered by Part A or Part B.

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