What Part D is and when you can sign up

Part D is prescription drug coverage you add to Original Medicare (Parts A and B) or to a Medicare Advantage plan. It covers the cost of medications your doctor prescribes. You do not have to take it, but if you go without coverage for a long time and then sign up later, you will pay a permanent penalty on your monthly premium.

You can sign up for Part D during your Initial Enrollment Period, which starts three months before the month you turn 65 and ends three months after. If you miss this window, you can sign up during the Annual Enrollment Period from October 15 to December 7 each year, with coverage starting January 1. If you have coverage through an employer or union and lose it, you have 63 days to sign up without penalty.

Part D plans are run by private insurance companies approved by Medicare. Each plan has its own list of covered drugs, costs, and pharmacies. You choose which plan to join based on the medications you take and where you fill prescriptions.

Key Takeaways

  • Part D is optional but carries a lifetime penalty if you delay signing up after your Initial Enrollment Period ends.
  • You pick a specific Part D plan during enrollment, and different plans cover different drugs at different costs.
  • You can compare plans free using Medicare's online tool, which shows your out-of-pocket costs based on your actual medications.
  • If you have Original Medicare, you buy Part D separately; if you have Medicare Advantage, it is usually included but you should check your plan documents.
  • You can change plans once a year during the Annual Enrollment Period if your medications or costs change.

How to find and compare Part D plans

Go to Medicare.gov and use the Plan Finder tool. You will need to enter your zip code and the medications you currently take. The tool shows you every Part D plan available in your area, ranked by your estimated out-of-pocket costs for those specific drugs.

The Plan Finder tells you the monthly premium for each plan, what you pay at the pharmacy (your copay or coinsurance), and which pharmacies are in the plan's network. It also shows you the deductible — the amount you pay out of pocket before the plan starts paying — which varies by plan and can be zero.

You do not need to use the Plan Finder, but it is the fastest way to see real numbers for your situation. You can also call 1-800-MEDICARE to speak with someone who can walk you through the options, or contact Part D plans directly by phone to ask questions about specific drugs.

The difference between Original Medicare and Medicare Advantage plans

If you have Original Medicare (Parts A and B), you buy Part D as a separate policy from a private insurance company. You choose your plan, enroll, and pay the premium directly to the insurance company. You keep your Original Medicare coverage and add Part D on top of it.

If you have a Medicare Advantage plan, prescription drug coverage is usually built in, though some plans do not include it. Check your plan documents or call the plan to confirm whether Part D is included. If it is not, you can add a separate Part D plan. If your Medicare Advantage plan does include Part D, you cannot also buy a standalone Part D plan — you must use the coverage in your Advantage plan.

The choice between Original Medicare and Medicare Advantage affects which Part D plans you can choose. This is one reason to review your coverage each year during Annual Enrollment: your best plan option may change if you switch between Original Medicare and Medicare Advantage.

What Part D costs and how the coverage works

Part D costs have three main parts: the monthly premium, the deductible, and the copay or coinsurance at the pharmacy. The monthly premium is what you pay to the insurance company each month. The deductible is the amount you pay out of pocket before the plan starts to help pay for drugs. The copay or coinsurance is what you pay each time you fill a prescription.

Most plans have a coverage gap, sometimes called the "donut hole." Once you and your plan have spent a certain amount on drugs in a year, you enter the gap and pay more out of pocket until you reach catastrophic coverage. In catastrophic coverage, the plan pays most of the cost and you pay a small copay. The exact amounts change each year.

Some plans have no deductible or a low one. Some plans charge a flat copay (for example, $5 for a generic drug), while others charge coinsurance (a percentage of the drug's cost). The Plan Finder shows you the total you would pay for your medications under each plan, so you can compare the real cost, not just the premium.

How to enroll in a Part D plan

You can enroll online at Medicare.gov, by phone at 1-800-MEDICARE, or by mail. Online enrollment is the fastest: go to Medicare.gov, log into your account (or create one), find the plan you want, and complete the enrollment form. You will need your Medicare number, which is on your Medicare card.

By phone, call 1-800-MEDICARE and tell the representative which plan you want to join. They will confirm your information and enroll you. By mail, you can request an enrollment form from Medicare and mail it to the address on the form.

Once you enroll, the insurance company will send you a confirmation letter and your plan documents. Your coverage starts on the first day of the month after you enroll, unless you enroll between October 15 and December 7, in which case coverage starts January 1. Keep your confirmation letter and plan documents — you will need them to know your copays, your pharmacy network, and how to file a claim if needed.

What to do if your medications or costs change

If your doctor prescribes a new medication or stops a medication, your out-of-pocket costs under your current plan may change. You can switch to a different Part D plan once a year during the Annual Enrollment Period (October 15 to December 7). Use the Plan Finder again with your updated medication list to see if a different plan would cost less.

If a drug you take is no longer covered by your plan, or if the plan stops covering it at the same cost, you can ask your doctor for an alternative drug that is covered. You can also ask the plan to make an exception and cover the drug anyway — this is called a formulary exception. The plan may approve it, especially if you have been taking the drug for a long time and switching would harm your health.

If you cannot afford your copays, some drug manufacturers offer patient information programs that reduce or cover the cost. Your pharmacist or doctor's office can help you find these programs. Some nonprofits also help seniors pay for medications.

When to contact Medicare or your Part D plan

Contact Medicare at 1-800-MEDICARE if you have questions about whether you need Part D, when you can sign up, or how to use the Plan Finder. They can also help if you think you should have been exempt from the late enrollment penalty.

Contact your Part D plan directly if you have questions about your coverage, your copays, whether a specific drug is covered, or which pharmacies are in your network. The phone number is on your plan documents and your insurance card. You can also contact your plan if you need to file a complaint about a denied claim or a coverage decision.

Contact your doctor or pharmacist if you cannot afford a medication or if a side effect is a problem. They may know of lower-cost alternatives or programs to help you pay.

Frequently Asked Questions

Do I have to take Part D if I am on Original Medicare?

No, Part D is optional. However, if you do not sign up when you are first may be able to access and you go without coverage for more than 63 days, you will pay a permanent penalty added to your monthly premium for as long as you have Part D. The penalty is about 1% of the national average Part D premium for each month you were without coverage.

Can I change Part D plans if I do not like the one I chose?

Yes, but only during the Annual Enrollment Period from October 15 to December 7. You can switch to a different plan, and your new coverage will start January 1. If your plan stops covering a drug you need or raises your copay significantly, you may be able to switch outside the enrollment period — contact your plan to ask.

What happens if my Part D plan stops offering coverage in my area?

Medicare will notify you by mail. You will have a special enrollment period to switch to a different Part D plan without waiting for the Annual Enrollment Period. Follow the instructions in the letter Medicare sends you.

Can I use my Part D coverage at any pharmacy?

No, each Part D plan has a network of pharmacies where your copay applies. If you use an out-of-network pharmacy, you will pay more or the plan may not cover the drug at all. The Plan Finder and your plan documents show you which pharmacies are in your network. If your regular pharmacy is not in the network, you can ask your plan to add it or switch to a plan that includes it.

What if I cannot afford my Part D copays?

Talk to your doctor or pharmacist about lower-cost alternatives. Ask the drug manufacturer if they offer a patient information program. Contact your local Area Agency on Aging to learn about programs that help seniors pay for medications. Some nonprofits and community health centers also offer financial help.