What is Medicare Part D?

Understand what Medicare Part D covers, what it costs and how it works with your Medicare coverage.

Page last updated on: 7/13/26

What is Medicare Part D?

Part D differs from other parts of Medicare because it helps cover prescription drug costs, unlike Original Medicare.

How does Medicare Part D work?

If you already have Medicare Parts A and B, you have two options for Part D coverage:

  • You can choose a Medicare Advantage plan (Part C) that includes prescription drug coverage (MAPD). MAPD plans are offered through a private insurance company, like Priority Health.
  • You can enroll in a stand-alone Medicare Part D prescription drug plan (PDP).

Who is eligible?

To get Medicare prescription drug coverage (Part D), you must be enrolled in Medicare Part A, Part B or both. If you have Original Medicare, you can enroll in a separate Part D drug plan.

If you choose a Medicare Advantage plan, prescription drug coverage is usually included, but it's important to check your plan's details because not all Medicare Advantage plans offer drug coverage.

When can I enroll?

The sooner you apply for Part D, the better. Ideally, this is done during your initial enrollment period.

If you choose not to enroll in a Medicare Part D prescription drug plan when you're first eligible, and you don't have other prescription drug coverage that is considered as good as Medicare's coverage (called creditable coverage), you may have to pay a late enrollment penalty.

This penalty is added to your monthly Part D premium and usually lasts for as long as you have Medicare prescription drug coverage. The amount is calculated by taking 1% of the national base beneficiary premium for each month you were eligible for Part D but did not enroll. The longer you wait, the higher the penalty may be.

If you take prescription drugs, you should consider Medicare Part D prescription drug coverage. Original Medicare (Parts A and B) doesn't cover most drugs. If you don't have a Medicare Part D plan or other drug coverage, you'll pay for your drugs out of your pocket, which can really add up.

Part D may help lower your prescription drug costs and help protect you against higher costs in the future.

No. Medicare Part D monthly premiums, copayments and deductibles vary from one insurer to the next. 

You can check if your drugs are covered by using the Priority Health formulary, a list of approved drugs. You can also see your estimated drug costs by plan. If your prescription drugs are not in the formulary, Priority Health Medicare members can request an exception.

In 2026, your annual out-of-pocket costs for covered Medicare Part D prescription drugs are capped at $2,100. After you reach that limit, you will pay $0 for covered Part D prescriptions for the remainder of the calendar year.

Before reaching the cap, what you pay for your medications depends on your plan. Drugs are grouped into different tiers, and each tier has its own cost. You may pay either a copay (a set amount) or coinsurance (a percentage of the drug's cost) when you fill a prescription.

What is Medigap?

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See how Medigap works

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