The Basic Rule for Medicare Part D

You can enroll in Medicare Part D if you already have Medicare Part A or Part B. Part D is the prescription drug coverage piece of Medicare — it is not a separate program you join on its own. If you are 65 or older and signed up for Medicare, or if you are younger but may have access to for Medicare because of a disability or end-stage renal disease, you can choose a Part D plan.

The main catch is timing. You have a limited window to enroll when you first become Medicare-may be able to access, and if you miss it without a good reason, you pay a permanent penalty on your premiums for as long as you have Part D. That penalty is small — usually a few dollars per month — but it never goes away, so the enrollment important date matters more than it might seem.

Key Takeaways

  • You must have Medicare Part A or Part B before you can enroll in Part D; Part D is prescription drug coverage only and does not stand alone.
  • You have seven months to enroll starting the month you turn 65 or the month your Medicare coverage begins, and missing this window triggers a permanent penalty.
  • If you already have drug coverage through an employer or union plan, you may be able to delay Part D enrollment without penalty, but you must confirm this with your plan first.
  • Part D plans vary widely in cost, deductibles, and which drugs they cover, so comparing plans each year during open enrollment can save you money.
  • You can switch Part D plans once per year during the annual enrollment period from October 15 to December 7.

When You Turn 65 and Become Medicare-may be able to access

If you are turning 65, your enrollment window for Part D opens three months before the month you turn 65 and closes three months after. That gives you seven months total. For example, if you turn 65 in June, you can enroll from March through September. The coverage starts on the first day of the month you turn 65 if you enroll by the end of that month; if you enroll later, coverage starts the first day of the following month.

You do not have to enroll in Part D at all if you do not want it. But if you go without Part D coverage and later decide you want it, you will owe that permanent penalty unless you had other drug coverage that counted as "creditable coverage" during the time you were uninsured. Creditable coverage means coverage that is at least as good as Part D — usually an employer plan, a union plan, or TRICARE for military families.

If You Are Younger Than 65 but may have access to for Medicare

You can get Medicare before 65 if you have been receiving Social Security Disability Insurance (SSDI) for 24 months, or if you have end-stage renal disease (ESRD) or ALS. Your Part D enrollment window works the same way: seven months starting three months before the month your Medicare coverage begins.

If you are on SSDI and your benefits end — for example, because you return to work — your Medicare coverage ends too, usually after a trial work period. Part D coverage ends at the same time. You will have a new enrollment window if you become may be able to access for Medicare again later.

If You Have Drug Coverage Through Work or a Union

If your employer or union offers health insurance with prescription drug coverage, you may be able to delay Part D enrollment without triggering the permanent penalty. This is called having "creditable coverage." The key word is may — not all employer plans count as creditable, and you have to check with your plan administrator or your employer's benefits office to be sure.

Do not assume your coverage is creditable just because it covers drugs. Some plans do not meet Medicare's standard. If you are unsure, contact your employer's human resources or benefits department and ask them directly whether your plan is creditable for Medicare purposes. If it is, ask them to send you a written notice saying so — you will need this if you ever have to prove you had creditable coverage.

When you do lose that employer coverage — usually when you retire or leave the job — you have 63 days to enroll in Part D without penalty. This is called a Special Enrollment Period. If you miss this 63-day window, the penalty applies.

If You Are Already on Medicare but Have Not Enrolled in Part D

If you missed your initial enrollment window, you can still enroll in Part D, but you will owe the permanent penalty unless you had creditable coverage the whole time you were uninsured. The penalty is calculated based on how many months you went without Part D or creditable coverage.

You can enroll during the annual open enrollment period, which runs from October 15 to December 7 each year. Coverage begins January 1 of the following year. You can also enroll if you may have access to for a Special Enrollment Period — for example, if you just lost employer coverage or if you move to a different state.

How to Enroll in Part D

You can enroll through Medicare.gov, by calling Medicare at 1-800-MEDICARE, or by visiting your local Social Security office. You can also enroll through an insurance agent or broker who represents Part D plans in your area. If you need help in a language other than English, Medicare offers free interpreter services.

When you enroll, you will choose a specific Part D plan offered by a private insurance company. Medicare does not run Part D plans; private insurers do. Each plan has its own list of covered drugs, its own cost-sharing structure, and its own pharmacy network. Comparing plans before you choose is worth the time, because the difference in your out-of-pocket costs can be significant.

Special Cases: Medicaid, Dual may be able to access, and Low-Income Help

If you have both Medicare and Medicaid (called "dual may be able to access"), you are automatically enrolled in a Part D plan chosen by your state Medicaid program. You can switch to a different plan during open enrollment if you want, but you do not have to do anything to get coverage.

If your income is low, you may may have access to for the Low-Income Subsidy (LIS), which helps pay your Part D premiums and cost-sharing. You can explore for LIS through Social Security or your state Medicaid office. If you may have access to, your out-of-pocket costs are capped, and you may pay little or nothing for your prescriptions.

Frequently Asked Questions

What happens if I do not enroll in Part D when I first become may be able to access?

You can still enroll later, but you will owe a permanent penalty on your premiums unless you had creditable coverage the entire time you were uninsured. The penalty is roughly 1% of the national average Part D premium for each month you were without coverage. This penalty stays with you as long as you have Part D.

Can I switch Part D plans if I do not like mine?

Yes. You can change plans once per year during the annual open enrollment period from October 15 to December 7. Your new coverage starts January 1. If you have a may have access to life event — such as moving, losing coverage, or a major change in your health — you may be able to switch outside this window.

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

Most Part D plans have a preferred pharmacy network, and you save money by using those pharmacies. You can usually use out-of-network pharmacies, but you will pay more. Check your plan's pharmacy list before you enroll to make sure your regular pharmacy is included.

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

You can ask your doctor to prescribe a different drug that the plan does cover, or you can request an exception from the insurance company. The plan must respond to exceptions within 72 hours for urgent requests. You may have to pay out of pocket if the exception is denied and you choose to take the uncovered drug anyway.

Does Part D cover all types of drugs?

No. Part D does not cover drugs used for weight loss, most over-the-counter medications, or drugs that Medicare Part B already covers (like insulin you inject yourself, which Part B covers). Each Part D plan also has its own formulary — the list of drugs it covers — so coverage varies by plan.