How Part D enrollment works

Medicare Part D is prescription drug coverage you add to Original Medicare (Parts A and B) or to a Medicare Advantage plan. You do not enroll in Part D through Medicare directly — instead, you choose a plan offered by a private insurance company that has a contract with Medicare, then that company handles your enrollment.

The process depends on when you first become may be able to access for Medicare. If you sign up during your initial enrollment period, you can avoid a late penalty. If you miss that window, you can still enroll, but you may pay more for coverage for as long as you have Part D.

Part D plans change every year — the drugs they cover, the pharmacies in their network, and the costs all shift on January 1. Even if you already have Part D, you need to review your plan each fall to see if it still fits your needs and budget.

Key Takeaways

  • You enroll in Part D through a private insurance company, not directly through Medicare, by visiting Medicare.gov, calling 1-800-MEDICARE, or working with a licensed insurance agent.
  • Your initial enrollment period is the three months before, the month you turn 65, and the three months after — missing this window triggers a permanent penalty on your premiums.
  • Part D plans cover different drugs at different costs, so you should use the Medicare Plan Finder tool to compare plans based on the specific medications you take.
  • Open enrollment runs from October 15 to December 7 each year, and any changes you make take effect on January 1.
  • If you have limited income, you may pay little or nothing for Part D premiums and out-of-pocket costs through the Low-Income Subsidy program.

When you can enroll in Part D

Your initial enrollment period is seven months long: the three months before the month you turn 65, the month you turn 65, and the three months after. If you enroll during this window, your coverage starts the first day of the month you turn 65 (or the first day of the month after you enroll, whichever is later). For example, if you turn 65 in June, you can enroll anytime from March through September, and coverage would start June 1.

If you miss your initial enrollment period and do not have other creditable prescription drug coverage (coverage as good as or better than Part D), you will pay a late enrollment penalty for as long as you have Part D. The penalty is 1% of the national average Part D premium for each month you were not enrolled. In 2024, that penalty was roughly $1 per month of delay, but the amount changes yearly. This penalty is added to your premium every month.

If you already have Part D, you can change plans or drop coverage during open enrollment, which runs from October 15 through December 7 each year. Any changes take effect on January 1. You can also switch plans if you move to a new state, lose your current coverage, or may have access to for a Special Enrollment Period due to a life event like retirement or loss of employer coverage.

How to find and compare Part D plans

Start by listing the prescription drugs you take, including the dose and how often you take them. You will need this list to compare plans accurately. The Medicare Plan Finder tool at Medicare.gov lets you enter your medications and see which plans cover them, what your out-of-pocket costs would be at different pharmacies, and whether your doctors and pharmacies are in each plan's network.

Part D plans fall into a few categories. A stand-alone Prescription Drug Plan (PDP) works with Original Medicare. A Medicare Advantage plan with Part D (often called MA-PD) combines medical coverage and drug coverage in one plan. Some people with Original Medicare choose not to add Part D if they have other coverage or do not take regular medications, though this can trigger the late penalty if they enroll later.

When you compare plans, look at the monthly premium, the deductible (the amount you pay before the plan starts to help), copayments or coinsurance for each drug, and whether your pharmacy is in the plan's network. Costs can vary widely — one plan might charge $5 for a generic drug while another charges $50 for the same medication. The Plan Finder shows you the total estimated cost for your specific drugs under each plan.

Steps to enroll in Part D

You have three main ways to enroll: online at Medicare.gov, by phone at 1-800-MEDICARE (1-800-633-4227), or in person with a licensed insurance agent or at your local Social Security office.

Online enrollment: Go to Medicare.gov, log in or create an account, and select "Enroll in a plan." The Plan Finder will walk you through comparing plans and choosing one. Once you select a plan, you complete the enrollment form on that plan's website or through Medicare. Enrollment usually takes 15 to 30 minutes.

Phone enrollment: Call 1-800-MEDICARE and tell the representative you want to enroll in Part D. They can answer questions about plans, help you compare options, and submit your enrollment. The call may take 30 to 45 minutes. Have your medications and pharmacy information ready.

In-person enrollment: A licensed insurance agent can walk you through your options and help you enroll. You can find agents through Medicare.gov or by calling 1-800-MEDICARE. Some agents work for specific insurance companies, while others are independent and can show you plans from multiple companies. There is no cost to work with an agent — they are paid by the insurance companies.

After you enroll, the insurance company will send you a confirmation letter with your member ID, plan details, and coverage start date. Keep this letter. You should receive your insurance card in the mail before your coverage starts, but you can use the member ID number to fill prescriptions at the pharmacy right away.

What happens if you have low income

If your income is at or below 150% of the federal poverty level, you may be able to get help paying for Part D premiums and out-of-pocket costs through the Low-Income Subsidy (LIS) program, also called "Extra Help." In 2024, that income limit was roughly $1,500 per month for an individual, but the limit changes yearly and varies by state.

You can explore for LIS through Social Security by visiting your local office, calling 1-800-772-1213, or explore online at ssa.gov. You can also explore through your state Medicaid office. The process asks about your income, resources (savings and investments), and citizenship. If you are approved, Social Security will send you a notice showing your subsidy amount. You do not need to do anything else — the insurance company will automatically explore the subsidy to your account.

With LIS, you typically pay $0 to $5 per prescription, and the program covers most or all of your Part D premium. Some people with LIS are automatically enrolled in a plan if they do not choose one themselves; Social Security will tell you if this applies to you.

What to do after you enroll

Once your Part D coverage starts, make sure your pharmacy has your correct member ID and date of birth. Test your coverage by filling a prescription early if you can, so you know what your copayment will be and whether there are any problems. If a drug is not covered or costs more than you expected, ask your doctor or pharmacist about alternatives, or contact your plan to ask about an exception.

Keep track of your out-of-pocket spending throughout the year. Part D has a coverage gap (sometimes called the "donut hole") where you pay a larger share of drug costs after you and your plan have spent a certain amount. In 2024, the gap started after $5,850 in total drug costs. Once your out-of-pocket spending reaches $8,550, catastrophic coverage kicks in and you pay only a small copayment for the rest of the year. Your plan's materials will explain how the gap works for your specific plan.

In October, review your current plan using the Plan Finder again. Your medications may have changed, plan costs may have shifted, or a better option may have become available. If you want to switch plans, you must do so during open enrollment (October 15 to December 7). If you do not make a change, your current plan will automatically renew for the next year.

Common reasons Part D enrollment gets delayed

Many people delay enrolling because they think they do not take enough medications to need Part D, or because they are still working and have employer coverage. If your employer coverage ends, you have 63 days from the date it ends to enroll in Part D without triggering the late penalty — this is called a Special Enrollment Period. Get written proof from your employer of when coverage ended, because you will need it if you enroll later.

Others delay because they are confused about whether they need Part D if they have Medicare Advantage. If you choose a Medicare Advantage plan, most include Part D automatically, but some do not. Check your plan documents or call the plan to confirm. If your Medicare Advantage plan does not include drug coverage and you do not enroll in a stand-alone Part D plan, you will face the late penalty.

Some people think they can enroll anytime because Medicare is federal. In fact, enrollment periods are strict, and missing your initial period costs you permanently. The only exceptions are Special Enrollment Periods for specific life events (like moving, losing coverage, or becoming may be able to access for Medicaid) and the annual open enrollment window in the fall.

Frequently Asked Questions

What if I do not take any prescription medications right now?

You should still enroll in Part D during your initial enrollment period to avoid the late penalty. Even if you do not fill prescriptions now, you may need medications later, and the penalty applies for the entire time you have Part D. The premium for a plan with no usage may be low, and it protects you from a much larger penalty down the road.

Can I change Part D plans in the middle of the year?

No, unless you may have access to for a Special Enrollment Period. These include moving to a new state, losing your current coverage, becoming may be able to access for Medicaid or Extra Help, or having a major life change. If none of these explore, you must wait until open enrollment in October to switch plans. If your medication or situation changes urgently, contact your current plan to see if they can make an exception or adjust your coverage.

What if my doctor prescribes a drug that my Part D plan does not cover?

Ask your doctor if there is a similar drug on your plan's formulary (the list of covered drugs) that would work for you. If not, you can request a coverage exception from your plan, which your doctor must submit in writing. The plan has 72 hours to respond. You can also appeal if the plan denies your request. In the meantime, you may have to pay out of pocket or wait until January 1 to switch to a plan that covers the drug.

Do I have to use the pharmacy in my Part D plan's network?

Most plans charge much less if you use an in-network pharmacy. You can use an out-of-network pharmacy, but you will pay more and may have to pay upfront and file for reimbursement. Check your plan's pharmacy directory before you enroll to make sure your regular pharmacy is included. If it is not, you can choose a different plan during open enrollment.

What if I cannot afford my Part D premiums and copayments?

Contact your plan's customer service to ask about patient information programs, which some drug manufacturers offer for free or low-cost medications. Also look into whether you may have access to for the Low-Income Subsidy program through Social Security. If your income is low enough, the subsidy can reduce or eliminate your premiums and copayments. You can explore anytime during the year.