Medicare Part D is not mandatory for everyone, but you face a penalty if you go without coverage when you are supposed to have it

You must enroll in Medicare Part D (prescription drug coverage) if you are on Medicare and want to avoid a late enrollment penalty — but the rule has important exceptions. If you have other drug coverage that is at least as good as Medicare's, you do not have to join Part D. If you delay enrollment without that other coverage, Medicare adds a permanent surcharge to your premium. The penalty amount depends on how long you went without coverage and changes each year.

The people who face the steepest penalties are those who drop Part D coverage and then try to rejoin later. Medicare counts every month you were without Part D or comparable coverage, and the penalty stays with you for life.

Key Takeaways

  • You must enroll in Part D when you first become may be able to access for Medicare, or during your Initial Enrollment Period, to avoid a permanent penalty.
  • If you have drug coverage through an employer, union, or retiree plan that is at least as good as Medicare Part D, you can skip Part D without penalty.
  • The late enrollment penalty is calculated based on the national average Part D premium and increases for each month you delay without creditable coverage.
  • If you lose other drug coverage, you have 63 days to enroll in Part D without triggering a penalty.
  • You can enroll, disenroll, or switch Part D plans during the Annual Enrollment Period (October 15 to December 7 each year) with no penalty.

Who must enroll in Part D

You must enroll in Part D if you are on Medicare (Part A or Part B) and do not have other drug coverage that Medicare considers creditable coverage. Creditable coverage means your current plan covers prescription drugs in a way that is at least as good as Medicare Part D. This includes drug coverage through an employer, a union, the Veterans Health Administration, TRICARE, or a state pharmacy information program.

The enrollment requirement kicks in when you first become may be able to access for Medicare. For most people, that is the month you turn 65. If you do not enroll during your Initial Enrollment Period — which runs for seven months, starting three months before the month you turn 65 — you will owe a penalty when you eventually join.

If you are already on Medicare but did not enroll in Part D at that time, you can still join during the Annual Enrollment Period, which runs from October 15 to December 7 each year. Enrollment takes effect January 1 of the following year.

When you can skip Part D without penalty

You do not have to enroll in Part D if you have creditable drug coverage through another source. The most common reason people skip Part D is that they still work and have health insurance through their employer or union. If that plan includes prescription drug coverage, you can stay on it and delay Part D enrollment without penalty — as long as your coverage remains creditable.

Before you decide to skip Part D, ask your current plan administrator whether your drug coverage is creditable. They can give you a written statement confirming it. Keep this document; you will need it if you ever want to prove you had creditable coverage when you delayed Part D enrollment.

Other sources of creditable coverage include retiree health plans, TRICARE (military coverage), the Veterans Health Administration, and some state Medicaid programs. If you are unsure whether your coverage counts, contact your plan directly or call Medicare at 1-800-MEDICARE.

What happens if you miss your enrollment window

If you do not enroll in Part D during your Initial Enrollment Period and you do not have creditable coverage, Medicare charges you a late enrollment penalty. The penalty is calculated as 1% of the national average Part D premium for each full month you were without Part D or creditable coverage. That percentage is applied to your premium every month for as long as you have Part D — it does not go away.

The national average premium changes each year, so the dollar amount of your penalty changes too. In 2024, the national average premium was around $34 per month, which means a one-year delay without creditable coverage would add roughly $4 per month to your premium permanently. A five-year delay would add roughly $20 per month. These amounts are examples; your actual penalty depends on the year you should have enrolled and the year you actually enroll.

The penalty applies even if you enroll later during a future Annual Enrollment Period. There is no way to avoid it once you have missed your Initial Enrollment Period without creditable coverage.

What to do if you lose other drug coverage

If you have creditable coverage through an employer or union and that coverage ends — because you retire, lose your job, or your employer drops the plan — you have a Special Enrollment Period of 63 days to join Part D without penalty. This 63-day window starts the day your other coverage ends.

You must enroll during this 63-day window to avoid the late enrollment penalty. If you wait until the next Annual Enrollment Period, you will owe a penalty for the months between when your coverage ended and when you enrolled in Part D.

When you enroll during your Special Enrollment Period, bring proof that your previous coverage ended — a letter from your employer, a final pay stub showing the end date of coverage, or a notice from your plan. Medicare may ask for this documentation.

How to enroll in Part D

You can enroll in Part D through Medicare.gov, by phone at 1-800-MEDICARE, or by visiting your local Social Security office. You will need your Medicare card and information about any current drug coverage you have.

When you enroll, you choose a specific Part D plan. Different plans cover different drugs and have different costs. You can compare plans on Medicare.gov using the Plan Finder tool, which shows you the estimated cost of your current medications under each plan in your area.

If you enroll during the Annual Enrollment Period (October 15 to December 7), your coverage starts January 1. If you enroll during your Initial Enrollment Period or a Special Enrollment Period, your coverage start date depends on when you enroll.

Changing or dropping Part D coverage

Once you are enrolled in Part D, you can switch to a different Part D plan or drop coverage altogether during the Annual Enrollment Period each year. Any changes you make during this period take effect January 1 of the next year.

If you drop Part D coverage and do not have creditable coverage elsewhere, you will owe a late enrollment penalty if you rejoin later. The penalty is based on how long you were without Part D or creditable coverage. For this reason, most people who are on Medicare should keep Part D coverage even if they do not use it much, or make sure they have creditable coverage through another plan.

If you want to drop Part D because the cost is too high or the plan does not cover your drugs well, talk to Medicare or a counselor at your State Health Insurance information Program (SHIP) before you make a final decision. They can help you find a plan that works better for you.

Frequently Asked Questions

Do I have to enroll in Part D if I am still working and have employer health insurance?

No, if your employer plan includes drug coverage that is creditable, you can delay Part D enrollment without penalty. However, when you do retire or lose that coverage, you will have only 63 days to enroll in Part D before a penalty applies. Get written confirmation from your employer that your drug coverage is creditable, and keep it for your records.

What is the late enrollment penalty and how long does it last?

The late enrollment penalty is 1% of the national average Part D premium for each full month you were without Part D or creditable coverage. It is added to your premium every month for the rest of your time on Medicare. The penalty does not expire, and there is no way to remove it once it has been applied.

Can I enroll in Part D anytime, or only during certain periods?

You can enroll during your Initial Enrollment Period (seven months starting three months before you turn 65), the Annual Enrollment Period (October 15 to December 7 each year), or a Special Enrollment Period if you lose other coverage. Outside these windows, you cannot enroll unless you may have access to for a Special Enrollment Period.

What happens if I drop Part D and then want to rejoin later?

You can rejoin during the next Annual Enrollment Period, but you will owe a late enrollment penalty for every month you were without Part D or creditable coverage. The penalty is permanent and stays on your premium for life. It is usually better to stay enrolled in Part D even if you do not use it much.

How do I know if my current drug coverage is creditable?

Contact your plan administrator or employer benefits department and ask them directly. They should provide a written statement confirming whether your coverage is creditable under Medicare rules. Keep this document in case you need to prove you had creditable coverage when you delayed Part D enrollment.