Medicare Part D is an insurance plan that covers some of the cost of your prescription drugs.
Original Medicare does not pay for any of your prescription medication.
There are two ways to get Part D: purchase a standalone plan or receive it through a Medicare Advantage plan.
What does Medicare Part D cover?
The list of drugs covered on each Part D plan is called a formulary.
Plans place the drugs they cover into different lists, called tiers, on the formulary.
Both brand-name prescription drugs and generic drugs are included. Your plan’s formulary will include at least 2 drugs in the most commonly prescribed categories and classes.
Your plan may change its drug list during the year if drug therapies change, new drugs are released, or new medical information becomes available.
However, your plan’s provider will have to give you at least 30 days notice unless the FDA says the drug is unsafe or the medication’s producer stops making it.

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What drugs are not covered by Part D?
These drugs are not covered under any prescription drug plan:
- Weight loss or weight gain drugs
- Any drugs for hair growth
- Fertility drugs
- Drugs for erectile dysfunction
- Any over-the-counter drugs
Drugs that are covered by every Medicare Part D plan
Each Part D plan is required to cover all drugs in the following categories:
- HIV/AIDS treatment
- Antidepressants
- Antipsychotic medications
- Anticonvulsive treatments for seizure disorders
- Immunosuppressants
- Anticancer drugs (unless they are being covered under Part B)
Nearly every vaccine is covered under Part D unless they are paid for by Part B.
Costs associated with Part D
How much your premium is will depend on where you live. However, there are some costs you can compare when shopping plans:
- Premium
- Deductible
- Copays
- Late enrollment fee
Your initial enrollment period spans the three months before you turn 65 and the three months after your 65th birthday. If you miss this time period, you will pay the late enrollment fee for Part D.
Part D’s penalty is 1% of the national base premium per consecutive month that you went without coverage and then rounded to the nearest 10 cents. The national base premium is $32.74 per month in 2020. If you went an entire year without coverage, your late fee would be an additional $3.90 per month.