Medicare Part D is optional prescription drug coverage offered through private Medicare-approved plans. You can get it either as a separate Medicare drug plan that adds coverage to Original Medicare, or as part of a Medicare Advantage Plan or other Medicare health plan.
How Part D works
Each Part D plan has its own rules, costs, and list of covered drugs, called a formulary. That means two plans can cover different drugs and charge different amounts, so it is important to compare plans before you enroll.
In general, plans must cover a wide range of prescription drugs, but the exact drugs, pharmacies, and cost-sharing can still vary by plan. If a plan does not cover a drug you need, you or your prescriber may be able to ask for an exception.
Important coverage rule
If you join a Medicare Advantage Plan that does not offer drug coverage, in most cases you cannot add a separate Medicare drug plan. That is one reason to check drug coverage before you enroll in a Medicare health plan.
Do you need Part D if you do not take prescriptions now?
Medicare says you should still consider drug coverage even if you do not take prescription drugs now. One reason is to help you avoid a late enrollment penalty if you join a plan later. A delay in coverage can also limit your choices when you finally want to enroll.
Simple comparison
| How you get drug coverage | What to know |
|---|---|
| Separate Part D plan | Adds drug coverage to Original Medicare and some other coverage types. |
| Bundled with Medicare Advantage or another health plan | Drug coverage is included in the plan if the plan offers it. |
Checklist before you enroll
- Confirm whether you want separate Part D coverage or bundled coverage through another plan.
- Check the plan’s formulary to see whether it covers the prescriptions you use.
- Review pharmacy network rules and expected out-of-pocket costs.
- Make sure you understand whether your current health plan allows a separate drug plan.
FAQ
Is Part D required? No. It is optional.
Do all Part D plans cost the same? No. Costs and covered drugs vary by plan.
Why consider Part D early? Medicare says even people who are not taking prescription drugs now should consider coverage to avoid a late enrollment penalty later.
Check existing coverage before you enroll
To join a separate Part D plan, you need Part A or Part B and must meet the plan’s enrollment rules. A Part D late enrollment penalty may apply after a gap of 63 consecutive days or more without Part D or other creditable prescription coverage after your initial enrollment opportunity. People who qualify for Extra Help do not pay this penalty. Creditable coverage is expected to pay, on average, at least as much as Part D.
Ask your current benefits administrator for your coverage notice before changing employer or union insurance. Enrolling in Part D can affect that other coverage, including coverage for dependents. Keep the notice with your records.
Related coverage questions
- Medicare Part D Costs: Premiums, Deductibles and Annual Limits
- How to Compare Medicare Part D Plans
- Creditable Coverage: Part D Notices and Part B Enrollment Rules
When you can enroll or change coverage
For a separate Part D plan, you need Part A or Part B, residence in the plan’s service area and an enrollment period that applies to you. When first eligible at 65, the usual window spans the three months before your birthday month through the three months after it. Disability and other eligibility situations have different timing.
Annual Open Enrollment runs October 15–December 7, with changes generally starting January 1. January–March Medicare Advantage Open Enrollment is for current Advantage members; someone returning to Original Medicare can also join Part D. It is not a general switching window for people already in standalone Part D. A qualifying move or other event may provide a Special Enrollment Period; confirm its exact deadline.
Steps for switching a separate Part D plan
- Check your permitted enrollment period and the new plan’s current costs, network and coverage rules.
- Enroll through Medicare.gov, the plan or 1-800-MEDICARE.
- Keep the confirmation and verify the effective date.
- When the new coverage starts, the old drug coverage ends; a separate cancellation is normally unnecessary.
Before changing employer or retiree coverage, ask the benefits administrator about consequences. Dropping coverage without a replacement can cause a gap and potential late penalties.