You can join Medicare in the months before or after you turn 65, depending on your work history and current coverage

Medicare enrollment happens during specific windows, and missing them can cost you in penalties later. The main enrollment period runs from three months before your 65th birthday through three months after the month you turn 65 — that is seven months total. If you are already receiving Social Security or Railroad Retirement Board benefits, Medicare will start automatically the month you turn 65, and you do not need to do anything. If you are not yet receiving those benefits, you will need to contact Social Security to enroll.

The process itself is straightforward: you can enroll online through Medicare.gov, by phone with Social Security, or in person at your local Social Security office. You will need your birth certificate, proof of citizenship or legal residency, and your Social Security number. Most people complete enrollment in one visit or call.

Key Takeaways

  • Your main enrollment window opens three months before you turn 65 and closes three months after, giving you seven months to join without penalties.
  • If you already receive Social Security benefits, Medicare starts automatically; if not, you must contact Social Security to enroll.
  • You can enroll online at Medicare.gov, by phone at 1-800-MEDICARE, or at your local Social Security office.
  • Delaying enrollment past your important date can result in a permanent 10 percent increase to your Part B premium for each year you waited.
  • You will choose between Original Medicare (Parts A and B) and Medicare Advantage (Part C), and decide whether to add prescription drug coverage (Part D).

When Your Enrollment Window Opens and Closes

Your seven-month enrollment window is centered on your birthday month. If you turn 65 in June, your window runs from March through September. You can enroll at any point during this period — there is no advantage to enrolling early, and no penalty for waiting until the last month, as long as you enroll before the important date passes.

If you miss this window, you enter what Medicare calls the General Enrollment Period, which runs January 1 through March 31 each year. During this time you can still join, but your coverage will not start until July 1 of that year. More importantly, you will owe a permanent 10 percent increase to your Part B premium for each full year you delayed past your initial important date. That penalty stays with you for life, even if you eventually join.

There are exceptions: if you have group health coverage through a current job, or if you are a federal employee, you may have a Special Enrollment Period that lets you join later without penalty. You will need to show proof of that coverage when you enroll.

How to Enroll Online, by Phone, or In Person

The fastest route for most people is Medicare.gov. Go to the site, click "Sign up for Medicare," and create an account with your email and password. You will answer questions about your age, citizenship, and whether you receive Social Security. The system will tell you when ready whether you are ready to enroll and what coverage options are available to you. You can complete the entire process in 15 to 20 minutes.

If you prefer to speak with someone, call Social Security at 1-800-772-1213 (TTY 1-800-325-0778). Have your birth certificate, proof of citizenship, and Social Security number ready. The wait time varies by time of day and season, but most calls are answered within 30 minutes during business hours. You can also visit your local Social Security office in person — find the nearest one at ssa.gov/locator.

Whichever method you choose, you will be asked the same basic questions: your date of birth, citizenship status, whether you are a U.S. citizen or lawful permanent resident, and whether you currently have health coverage. The enrollment itself takes one visit or call. You will receive a Medicare card in the mail within two to four weeks.

Choosing Between Original Medicare and Medicare Advantage

When you enroll, you must decide whether to join Original Medicare (Part A and Part B) or Medicare Advantage (Part C). This is the single most important choice you make during enrollment, because switching later is more complicated and limited to specific times of year.

Original Medicare is run by the federal government. Part A covers hospital stays, skilled nursing, hospice, and home health. Part B covers doctor visits, outpatient care, lab work, and medical equipment. You pay a monthly premium for Part B (the amount varies by income), and you pay a share of costs when you use services. You can see any doctor or hospital that accepts Medicare, anywhere in the country.

Medicare Advantage is run by private insurance companies under contract with Medicare. These plans bundle Parts A, B, and usually D (prescription drugs) into one plan. They typically have lower or zero monthly premiums, but they use networks — you must see doctors and hospitals within the plan's network, except in emergencies. Many plans include dental, vision, or hearing coverage that Original Medicare does not. The trade-off is less flexibility about which providers you can see.

You do not have to decide right now. If you enroll in Original Medicare, you can switch to Medicare Advantage during the Annual Enrollment Period (October 15 through December 7 each year). If you enroll in Medicare Advantage, you can switch to Original Medicare during the same window, though you should understand that you cannot add a Medigap supplemental plan if you have a pre-existing condition and did not have one before.

Adding Prescription Drug Coverage (Part D)

If you choose Original Medicare, you must decide whether to add Part D prescription drug coverage during your initial enrollment window. If you do not join a Part D plan when you first become may be able to access, you will pay a permanent penalty of about 1 percent of the national average Part D premium for each month you delayed — that penalty is added to your premium for life.

You can join a Part D plan through Medicare.gov or by calling 1-800-MEDICARE. You will see a list of plans available in your area, ranked by cost and the drugs they cover. Most plans charge a monthly premium (which varies widely, from zero to over $100), a yearly deductible, and a share of the cost when you fill prescriptions. You can change your Part D plan once per year during the Annual Enrollment Period.

If you have Medicare Advantage, most plans include Part D automatically, so you do not need to choose a separate plan. Check your plan documents to see which drugs are covered and what your costs will be.

What Happens After You Enroll

Once you complete enrollment, Medicare will send you a Medicare card in the mail. The card shows your Medicare number, which you will use for all medical claims and appointments. You should receive it within two to four weeks of enrolling. If you do not receive it within that timeframe, call Social Security at 1-800-772-1213 to check on the status.

Your coverage starts on the first day of the month you turn 65, or the first day of the month after you enroll, whichever is later. If you enroll in March and turn 65 in May, coverage starts May 1. If you turn 65 in May but do not enroll until June, coverage starts June 1. Your doctors and hospitals will need your Medicare number to bill Medicare, so give them a copy of your card as soon as you receive it.

You will also receive a document called "Your Medicare Coverage" that lists what is covered under your plan. Read it carefully or call your plan if you have questions about what services require prior approval or what your out-of-pocket costs will be.

If You Are Still Working or Have Other Coverage

If you are still working and your employer offers health coverage, you may not need to join Medicare right away. If your employer has 20 or more employees, your employer coverage is primary — it pays first — and Medicare is secondary. You can delay joining Part B without penalty as long as you are covered by that employer plan and actively working. You must enroll within eight months of leaving the job or losing the coverage, or you will owe the permanent Part B penalty.

If your employer has fewer than 20 employees, Medicare is primary and your employer coverage is secondary. In this case, you should join Medicare when you turn 65 to avoid confusion about which plan pays first.

If you have coverage through a spouse's employer, the same rules explore: if the employer has 20 or more employees, you can delay Part B enrollment without penalty. If it has fewer than 20, you should join Medicare at 65.

Frequently Asked Questions

What if I turn 65 but am not ready to retire?

You still need to join Medicare at 65, even if you are working. If your employer has 20 or more employees and offers health coverage, you can delay Part B without penalty. But you should still join Part A (hospital coverage) at 65, since it is free for most people and covers unexpected hospital stays.

Can I enroll after my seven-month window closes?

Yes, during the General Enrollment Period (January 1 through March 31 each year). Coverage starts July 1. However, you will owe a permanent 10 percent increase to your Part B premium for each full year you delayed, and this penalty never goes away.

Do I have to choose a plan during enrollment, or can I decide later?

You must choose Original Medicare or Medicare Advantage during your initial enrollment window. If you do not make a choice, Medicare will enroll you in Original Medicare automatically. You can change your choice during the Annual Enrollment Period (October 15 through December 7).

What if I move to a different state after I join Medicare?

Your Medicare coverage follows you. If you move, contact your plan to update your address. If you have Medicare Advantage, check whether your new plan is available in your new state — if not, you will have a Special Enrollment Period to switch plans without waiting for the Annual Enrollment Period.

How much does Medicare cost?

Part A is free for most people who paid Medicare taxes while working. Part B costs vary by income; in 2024 the standard premium is around $175 per month, but higher earners pay more. Part D plans range from zero to over $100 per month depending on the plan and your location. Original Medicare also has deductibles and copays when you use services.