You enroll in Part D through Medicare, not through your doctor or pharmacy

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 sign up for it through your pharmacy or doctor — you enroll through Medicare directly, either online at Medicare.gov, by phone, or in person at a Social Security office.

Most people enroll during their Initial Enrollment Period, which is the seven-month window that starts three months before the month you turn 65. If you miss this window, you can still enroll during the yearly Annual Enrollment Period (October 15 to December 7 each year), but you may pay a penalty on your premiums for as long as you have Part D coverage.

If you already have prescription drug coverage through an employer or union, you may not need to enroll right away — but you should check whether your coverage is considered "creditable" (as good as or better than Medicare Part D). If it is not, you should enroll in Part D to avoid the penalty.

Key Takeaways

  • You enroll in Part D through Medicare.gov, by calling 1-800-MEDICARE, or at your local Social Security office during your Initial Enrollment Period (seven months starting three months before you turn 65).
  • Part D plans vary widely in cost and which drugs they cover, so comparing plans before you enroll helps you find one that matches your prescriptions and budget.
  • If you miss your Initial Enrollment Period and do not have other creditable drug coverage, you will pay a permanent penalty added to your Part D premium.
  • You can change Part D plans once a year during the Annual Enrollment Period (October 15 to December 7), or when ready if you lose other drug coverage.
  • Part D covers most prescription drugs, but each plan has its own formulary (list of covered drugs), and some drugs may require prior approval from your plan before the pharmacy will fill them.

Understanding the three ways to enroll

The fastest way to enroll is online at Medicare.gov. Go to the "Sign Up for Medicare" section, create a Medicare.gov account if you do not have one, and follow the steps to compare and choose a Part D plan. You can see the cost and coverage for each of your current medications before you enroll, which helps you pick the plan that works best for your budget and prescriptions.

If you prefer to enroll by phone, call 1-800-MEDICARE (1-800-633-4227). A Medicare representative can walk you through your options and help you enroll over the phone. The line is open 24 hours a day, seven days a week. Have your Medicare card and a list of your current medications ready when you call.

You can also enroll in person at your local Social Security office. Find the office nearest you at ssa.gov/locator. Bring your Medicare card and a list of your medications. Social Security staff can help you compare plans and complete your enrollment.

What happens after you enroll

Once you enroll, your Part D plan coverage begins on the first day of the following month. For example, if you enroll in November, your coverage starts December 1. Your plan will send you a membership card in the mail — keep it with you when you pick up prescriptions.

Before your coverage starts, review the plan's formulary (the official list of drugs it covers). You can find this on the plan's website or by calling the plan's customer service number, which will be on your membership card. If one of your current medications is not on the formulary, contact the plan to ask about coverage options — some drugs can be added to the formulary, or the plan may cover a similar drug instead.

When you fill a prescription at the pharmacy, show your Part D membership card. The pharmacy will check your coverage and tell you what you owe. Most plans have a deductible (an amount you pay before the plan starts paying), and then you pay a copay or coinsurance for each prescription.

How Part D plans differ and what to compare

No single Part D plan covers every drug or costs the same for every person. Plans differ in their monthly premium, deductible, copays, and which drugs they cover. A plan that is cheapest for one person may be expensive for another, depending on which medications they take.

Before you enroll, use the Medicare Plan Finder tool on Medicare.gov. Enter your medications, and the tool will show you the estimated yearly cost (premium plus out-of-pocket costs) for each plan in your area. This is the single best way to compare plans based on your actual prescriptions.

Pay attention to whether your preferred pharmacy is in the plan's network. Some plans charge more if you use an out-of-network pharmacy, and some do not cover mail-order prescriptions. If you use a specific pharmacy regularly, check that it is in-network before you enroll.

The penalty for missing your enrollment important date

If you do not enroll in Part D during your Initial Enrollment Period and you do not have other creditable drug coverage, Medicare charges you a late enrollment penalty. This penalty is added to your Part D premium for as long as you have Part D coverage — it does not go away after a few years.

The penalty is calculated based on how many months you went without Part D or creditable coverage. The longer you wait, the higher the penalty. For example, if you are six months late, your penalty will be higher than if you are one month late.

The only way to avoid the penalty is to have had creditable drug coverage (through an employer, union, Veterans Affairs, or another source) during the time you were not enrolled in Part D. If you did have creditable coverage, you will need to show proof of it when you enroll. Ask your former employer or coverage provider for a letter stating that your coverage was creditable.

When you can change your Part D plan

You can change Part D plans once a year during the Annual Enrollment Period, which runs from October 15 to December 7. Any changes you make take effect January 1 of the following year. This is the time to switch if your current plan no longer covers your medications well or if you find a cheaper option.

You can also change plans when ready if you have a may have access to life event, such as losing your job, moving to a different state, or losing other drug coverage. You have 63 days from the date of the event to enroll in a new plan. Contact Medicare to report the event and enroll.

If you are in a Medicare Advantage plan that includes drug coverage (Part C), you can switch to Original Medicare plus a standalone Part D plan during the Annual Enrollment Period. You can also switch from Original Medicare plus Part D to a Medicare Advantage plan with drug coverage during this same window.

What to ask your doctor before you enroll

Before you choose a Part D plan, talk to your doctor or pharmacist about your medications. Ask whether any of your prescriptions are likely to change in the coming year — if you are starting a new medication or stopping one, that affects which plan is cheapest for you.

Ask your doctor whether there are generic versions of your medications available. Generic drugs are usually much cheaper than brand-name drugs, and most Part D plans cover them. If your doctor prescribes a brand-name drug, ask whether a generic would work just as well.

If you take a medication that is expensive or not commonly prescribed, ask your doctor whether the plan you are considering covers it. Some plans require prior authorization before they will pay for certain drugs — this means the plan must approve the prescription before the pharmacy fills it. Your doctor's office can usually handle this, but it is good to know in advance.

Frequently Asked Questions

Do I have to enroll in Part D if I already take very few medications?

If you are on Original Medicare and do not have other drug coverage, you should still enroll in Part D even if you take few medications. If you do not enroll during your Initial Enrollment Period, you will pay a penalty later if you ever do enroll. The penalty is permanent, so it is better to enroll now and pay a low premium than to wait and face a higher cost later.

What if my Part D plan stops covering one of my medications?

Plans can change their formulary each year. If your plan stops covering a drug you need, you can ask your plan for a coverage exception — sometimes the plan will cover it anyway, or cover a similar drug instead. If the plan says no, you can switch to a different Part D plan during the next Annual Enrollment Period, or when ready if you can show the change caused a hardship.

Can I use my Part D coverage at any pharmacy?

Most Part D plans have a network of pharmacies where you pay the lower copay amount. If you use an out-of-network pharmacy, you may pay more or the plan may not cover the drug at all. Check your plan's pharmacy network before you fill a prescription at a new pharmacy.

What if I cannot afford my Part D premiums or copays?

If your income is low, you may may have access to for Extra Help, a federal program that pays Part D premiums and reduces copays. You can explore through Social Security (ssa.gov/benefits/medicare) or by calling 1-800-MEDICARE. Extra Help is based on income and has no asset limit, so even people with savings may may have access to.

Do I need to re-enroll in Part D every year?

No. Once you enroll in a Part D plan, your coverage continues automatically each year unless you change plans or lose Medicare coverage. However, you should review your plan each October during the Annual Enrollment Period to make sure it still covers your medications at a good price, because plans change their formularies and premiums every year.