Part D enrollment happens during specific windows, and missing your important date can cost you more later

Medicare Part D is prescription drug coverage you add to Original Medicare (Parts A and B) or to a Medicare Advantage plan. You enroll through insurance companies that offer Part D plans, not through Medicare directly — though Medicare.gov helps you compare plans and find which companies serve your area.

The main enrollment window is October 15 through December 7 each year. Coverage starts January 1 of the following year. If you miss this window, you can still enroll during your birthday month (the month you turn 65), but only if you are new to Medicare. After that, you face a late penalty on your premiums for as long as you have Part D coverage, unless you had other creditable drug coverage.

The process itself takes about 15 minutes: you pick a plan, give the insurance company your information, and they send you a confirmation. You do not need to contact Medicare.

Key Takeaways

  • The yearly enrollment window runs October 15 through December 7, with coverage starting January 1.
  • You enroll directly with insurance companies offering Part D plans in your area, not with Medicare.
  • If you miss the October-December window and are not new to Medicare, you will pay a permanent penalty on your premiums.
  • You can compare plans and see which ones cover your specific medications on Medicare.gov before you choose.
  • If you have other drug coverage (from an employer or union), you may not need Part D, but you should check whether it is creditable.

When you can enroll in Part D

The Initial Enrollment Period is the seven-month window that includes the month you turn 65, the three months before, 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 month after, depending on when you sign up. This is the only time you can enroll without a penalty if you do not already have Part D.

The Annual Enrollment Period runs October 15 through December 7 every year. Anyone with Medicare can switch plans or enroll in Part D during this time. Your new coverage takes effect January 1. If you already have Part D and want to stay with the same plan, you do not need to do anything — your coverage continues automatically.

If you miss both windows, you can only enroll during a Special Enrollment Period, which applies to specific situations: you lose other drug coverage, you move out of your plan's service area, your plan leaves the market, or you may have access to for Extra Help (a program that pays Part D costs for people with low income). You have 63 days from the event to enroll.

How to find and compare Part D plans

Go to Medicare.gov and use the Plan Finder tool. You will need your Medicare number (on your red, white, and blue Medicare card) and a list of your current medications, including the dose and how often you take them. The tool shows you every Part D plan available in your ZIP code, what each plan costs, and whether each one covers your drugs.

Part D plans vary widely in monthly premium, deductible, and how much you pay for each drug. Some plans have no deductible. Some charge a flat copay for each prescription; others use a tiered system where generic drugs cost less than brand-name drugs. A plan that is cheapest for one person may cost much more for another, depending on which drugs they take.

The Plan Finder shows you the estimated total cost for your medications under each plan for the year. Use this number to compare, not just the monthly premium. A plan with a higher premium might save you money overall if your drugs are cheaper under that plan.

Enrolling directly with an insurance company

Once you choose a plan, you enroll with the insurance company that offers it, not with Medicare. You can enroll online on the company's website, by phone, or by mail. The insurance company's phone number and website are listed on the Plan Finder results page.

You will need your Medicare number, date of birth, and contact information. The company will ask whether you have other drug coverage and whether you want automatic payments set up. Enrollment takes about 15 minutes by phone or online.

After you enroll, the insurance company sends you a confirmation letter with your plan details, member ID number, and the date your coverage starts. Keep this letter. You will need the member ID to fill prescriptions at the pharmacy.

What happens if you miss the 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, you will owe a late enrollment penalty for as long as you have Part D. The penalty is roughly 1% of the national average Part D premium for each month you were without coverage. In 2024, this is about $1 per month for each month late, but the amount changes yearly.

The penalty is added to your monthly Part D premium. It does not go away if you switch plans later. The only way to avoid it is to show that you had creditable coverage — meaning drug coverage as good as Part D — from an employer, union, Veterans Affairs, or another source during the time you were not enrolled in Part D.

If you had a gap in coverage and now want to enroll, you can do so during the next Annual Enrollment Period (October 15 through December 7) or if you may have access to for a Special Enrollment Period. The penalty applies from the month your coverage ended until the month your new Part D coverage starts.

Creditable coverage and when you might not need Part D

If you have drug coverage from a current or former employer, a union, Veterans Affairs, or another source, that coverage may be creditable — meaning it is at least as good as Part D. If it is creditable, you do not have to enroll in Part D right away. You can enroll later without a penalty, as long as you enroll within 63 days of losing that coverage.

Your employer or union should tell you in writing whether your coverage is creditable. The notice usually arrives in October or November. If you are not sure, contact your benefits administrator or your former employer's benefits office. Do not assume your coverage is creditable without confirmation in writing.

If you lose creditable coverage and do not enroll in Part D within 63 days, you will owe the late penalty. The 63-day clock starts the day your other coverage ends, not the day you find out it ended.

Extra Help paying for Part D

Extra Help is a federal program that pays Part D premiums, deductibles, and copays for people with limited income and resources. Your income limit depends on whether you live alone, are married, or support dependents. In 2024, the limit for a single person is roughly $21,000 per year, but this changes yearly and varies by state.

You can explore for Extra Help through Social Security (online at ssa.gov, by phone at 1-800-772-1213, or in person at your local Social Security office) or through your state Medicaid office. If you may have access to, Social Security will send you a notice and a list of plans available to you. You can then enroll in any Part D plan on that list.

If you receive Extra Help, you pay little to nothing for your prescriptions, depending on the plan you choose. Some plans charge $0 copays for all drugs. You should still compare plans because they cover different drugs and have different copays, even with Extra Help.

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 drugs have generic versions (which usually cost less) and whether your doctor would be willing to prescribe a generic if your plan covers it but not the brand name. Ask whether any of your drugs require prior authorization — meaning the insurance company must approve it before the pharmacy fills it — because some plans require this and others do not.

If you take a medication that is very expensive or not commonly prescribed, ask your doctor which plans in your area are most likely to cover it. Your doctor's office may have a list of plans they work with frequently.

When to contact Medicare or your insurance company

Contact Medicare (1-800-MEDICARE or Medicare.gov) if you have questions about whether you need Part D, whether you have a Special Enrollment Period, or how to use the Plan Finder. Contact your Part D insurance company if you have questions about a specific plan, how to enroll, or what your coverage will cost.

If you enroll and then realize you chose the wrong plan, you have until December 31 to switch to a different plan during the Annual Enrollment Period. If you enroll outside the Annual Enrollment Period (for example, during a Special Enrollment Period), you usually cannot switch plans until the next Annual Enrollment Period, unless you may have access to for another Special Enrollment Period.

Frequently Asked Questions

Do I have to enroll in Part D when I turn 65?

You do not have to, but if you do not have other creditable drug coverage and you wait, you will owe a late penalty. The penalty applies for as long as you have Part D. If you have drug coverage from an employer or union, check whether it is creditable before you decide.

Can I change my Part D plan after I enroll?

Yes, during the Annual Enrollment Period (October 15 through December 7). If you enroll outside this window, you usually cannot switch plans until the next Annual Enrollment Period, unless you have a may have access to event like moving or losing other coverage.

What if my medication is not covered by the plan I chose?

Contact your insurance company and ask about your options. Some plans will cover a drug if your doctor requests an exception. You can also switch to a different plan during the Annual Enrollment Period if you find one that covers your medication at a lower cost.

Do I need to enroll in Part D if I have a Medicare Advantage plan?

Most Medicare Advantage plans include drug coverage, so you do not need separate Part D. Check your plan documents to confirm. If your Medicare Advantage plan does not include drug coverage, you can enroll in Part D during the Annual Enrollment Period.

What happens if I do not use my Part D coverage?

You still pay the monthly premium. If you do not think you will need prescriptions, you can skip Part D during your Initial Enrollment Period, but you will owe a late penalty if you enroll later. If your situation changes and you need medications, you can enroll during the Annual Enrollment Period or a Special Enrollment Period.