What happens when you sign up for Part D

Part D is prescription drug coverage you add to Original Medicare (Parts A and B). When you sign up, you choose a plan run by a private insurance company, and that company covers some or all of your prescription costs depending on which plan you pick and what drugs you take.

You do not have to sign up for Part D — it is optional. But if you wait to join after your initial window closes, you will pay a penalty on your monthly premium for as long as you have Medicare, even if you sign up years later. The penalty is roughly 1 percent of the national average Part D premium for each month you were not covered.

Most people sign up during their initial enrollment period, which is the seven months that starts three months before the month you turn 65. You can also sign up during the annual open enrollment period, which runs from October 15 to December 7 each year, and coverage starts January 1.

Key Takeaways

  • You can sign up for Part D online through Medicare.gov, by phone at 1-800-MEDICARE, or in person at a local Social Security office.
  • Your initial enrollment period is seven months long — three months before the month you turn 65, the month you turn 65, and three months after.
  • Part D plans vary widely in cost and which drugs they cover, so comparing plans before you choose matters because you can only switch once a year.
  • If you miss your initial enrollment period and do not have other creditable drug coverage, you will pay a penalty added to your premium for the rest of your time on Medicare.
  • You can change Part D plans once per year during the annual open enrollment period from October 15 to December 7.

Where to sign up for Part D

You have three main routes to sign up: online, by phone, or in person.

Online through Medicare.gov: Go to Medicare.gov, click "Sign up for Medicare," and follow the steps. You will need your Social Security number, date of birth, and contact information. The site will show you all Part D plans available in your area and let you compare costs and which drugs each plan covers. This is the fastest route if you are comfortable using a computer.

By phone: Call 1-800-MEDICARE (1-800-633-4227). A representative will walk you through the plans available where you live and help you choose one. The line is open 24 hours a day, seven days a week. Have your Social Security number and information about any medications you take ready before you call.

In person: Visit your local Social Security office. You can find the nearest one at ssa.gov/locator. Bring your Social Security card, proof of citizenship or legal residency, and a list of your current medications. Staff there can help you compare plans and sign up on the spot.

What information you will need to have ready

Before you start the sign-up process, gather these documents and details so you do not have to stop halfway through.

You will need your Social Security number, date of birth, and contact information (address, phone number, email). You will also need to know your current medications — the name of each drug, the dose, and how often you take it. This helps the system show you which plans cover your specific drugs and at what cost.

If you have other insurance that covers prescriptions — through a current or former employer, a union, TRICARE, or the VA — have that information ready too. Some of these plans are considered "creditable coverage," which means you will not face a penalty if you delay joining Part D. The insurance company will tell you whether your coverage is creditable.

How to compare Part D plans before you choose

Part D plans differ in monthly premium, which drugs they cover, and how much you pay at the pharmacy. Picking the wrong plan can cost you hundreds of dollars a year, so comparing before you sign up matters.

Use the Medicare Plan Finder tool at Medicare.gov. Enter your medications, and the tool will show you every Part D plan in your area, ranked by estimated yearly cost. The cost includes your monthly premium plus what you will pay out of pocket for your drugs. Plans are color-coded: green means lower cost, yellow means medium, and red means higher.

Look at the formulary — the list of drugs each plan covers. Some plans cover all your medications; others might not cover one or two. If a plan does not cover a drug you need, you can ask the plan to make an exception, but that takes time and is not always approved. It is safer to pick a plan that already covers what you take.

Also check the pharmacy network. Each plan has a list of pharmacies where you pay the negotiated price. If you use a pharmacy outside the network, you pay more or the plan does not cover it at all. Make sure your regular pharmacy is in the plan's network.

The enrollment steps once you have chosen a plan

Once you have decided which plan to join, the actual sign-up takes about 15 minutes online or over the phone.

If you are signing up online at Medicare.gov, you will enter your personal information, confirm your medications, select your plan, and review a summary before you submit. You will get a confirmation number on screen — write it down. Medicare will send you a welcome packet in the mail with your member ID card, which you will need at the pharmacy.

If you are signing up by phone or in person, the representative will enter your information into the system while you are on the call or in the office. You will still receive your member ID card by mail. Coverage usually starts on the first day of the following month if you sign up before the 15th of the current month; if you sign up after the 15th, coverage starts the first day of the month after that.

What to do if you miss your initial enrollment period

If you did not sign up during your initial seven-month window and you do not have other creditable drug coverage, you have missed the main enrollment period. You can still join during the annual open enrollment period (October 15 to December 7), but you will owe a late penalty.

The penalty is calculated as 1 percent of the national average Part D premium for each full month you were not covered. As of 2024, the national average premium is around $34 per month, so the penalty might be roughly 34 cents per month of delay — but this amount changes each year. Once you join, this penalty is added to your monthly premium permanently.

If you have creditable coverage through an employer, union, TRICARE, or the VA, you do not owe a penalty when you eventually join Part D, as long as you sign up within 63 days of losing that coverage. Get a letter from your former plan stating that your coverage was creditable, because you will need to show it to Medicare.

Changing your Part D plan after you sign up

You can change to a different Part D plan once per year during the annual open enrollment period. This is useful if your medications change, your plan's costs go up, or you find a better option.

To switch plans, go to Medicare.gov, call 1-800-MEDICARE, or visit your local Social Security office between October 15 and December 7. Tell them you want to change plans and which new plan you want to join. Your new coverage will start January 1. Your old plan coverage ends December 31.

If you have a life-changing event — you move to a different state, lose employer coverage, or become may be able to access for Medicaid — you may be able to change plans outside the annual period. Call 1-800-MEDICARE to ask whether your situation qualifies.

Frequently Asked Questions

Can I sign up for Part D before I turn 65?

Yes. Your initial enrollment period starts three months before the month you turn 65. You can sign up as early as that three-month mark, and coverage can start as early as the month you turn 65. Signing up early means you will not miss the important date and avoid the late penalty.

What if I am already on Medicare but never signed up for Part D?

You can join during the annual open enrollment period from October 15 to December 7, and coverage will start January 1. If you missed your initial enrollment period, you will owe a late penalty added to your monthly premium. The penalty is roughly 1 percent of the national average Part D premium for each month you were not covered.

Do all Part D plans cover the same drugs?

No. Each plan has its own formulary — the list of drugs it covers. Some plans cover most common medications; others might not cover certain drugs. Before you sign up, use the Medicare Plan Finder to check whether your specific medications are covered by the plan you are considering.

What happens if my plan stops covering one of my medications?

You can ask the plan for an exception, which sometimes is approved. You can also switch to a different Part D plan during the annual open enrollment period if you find one that covers the drug you need. If you need the medication urgently and your plan denies the exception, talk to your doctor about whether a similar drug on your plan's formulary might work for you.

Can I sign up for Part D if I am still working and have employer health insurance?

Yes, but check whether your employer plan includes creditable drug coverage first. If it does, you do not have to join Part D right away — you can wait without penalty as long as you sign up within 63 days of losing that coverage. If your employer plan does not cover prescriptions, you should join Part D during your initial enrollment period to avoid the late penalty.