When and how to sign up for Medicare

You can sign up for Medicare starting three months before the month you turn 65. The enrollment window lasts seven months total — three months before, the month you turn 65, and three months after. If you miss this window, you may pay a penalty for as long as you have Medicare, so timing matters.

You have three main ways to sign up: online at Medicare.gov, by phone at 1-800-MEDICARE (1-800-633-4227), or in person at your local Social Security office. Online is fastest — you can complete it in about 15 minutes if you have your Social Security number and birth date ready. The phone line has wait times but staff can answer questions as you go. In-person enrollment at Social Security takes longer but works well if you need help understanding your options.

You do not have to wait until you turn 65 to start learning about your choices. Many people spend weeks comparing plans before they enroll, and that is the right approach. The enrollment window is firm, but your research window can start much earlier.

Key Takeaways

  • Your enrollment window opens three months before you turn 65 and closes three months after — missing it can cost you in penalties for years.
  • You can enroll online at Medicare.gov, by phone at 1-800-MEDICARE, or at your local Social Security office.
  • You will choose between Original Medicare (Parts A and B) and Medicare Advantage, and decide whether to add prescription drug coverage (Part D).
  • If you are still working and have health insurance through your job, you may be able to delay enrollment without penalty — ask your employer's benefits office.
  • Once you enroll, your coverage starts the first day of the month you turn 65 or the first day of the month after you sign up, whichever is later.

What you need before you enroll

Gather these documents before you start: your Social Security number, your birth date, your citizenship or immigration status, and information about any current health coverage (employer insurance, COBRA, or other plans). If you are enrolling by phone or in person, also have your address and phone number ready.

If you have employer health insurance through a current job, write down the name of your employer and your plan name. You will need this to tell Medicare whether you want to keep that coverage or switch. If you are on COBRA or a spouse's plan, note the plan name and when your coverage ends.

You do not need to bring original documents to Medicare.gov — the system will ask you to confirm information, not upload files. If you enroll by phone or in person, staff may ask you to verify details but will not ask for documents on the spot.

Choosing between Original Medicare and Medicare Advantage

This is your biggest decision. Original Medicare is run by the federal government and covers hospital stays (Part A) and doctor visits (Part B). You can see any doctor or hospital that accepts Medicare. You pay a monthly premium for Part B, and you pay a share of costs when you use care — a deductible, then coinsurance or copays.

Medicare Advantage is sold by private insurance companies and includes Parts A, B, and usually prescription drug coverage (Part D) all in one plan. Most Advantage plans have a $0 or low monthly premium, but you must use doctors and hospitals in the plan's network. You typically pay a copay for each visit instead of coinsurance. Advantage plans often include dental, vision, or hearing benefits that Original Medicare does not.

Original Medicare gives you more freedom to choose providers. Medicare Advantage usually costs less upfront but limits where you can go. Neither is "better" — it depends on your doctors, your budget, and how much care you expect to need. If your current doctor accepts Medicare, call their office and ask whether they accept Original Medicare, Medicare Advantage plans, or both. That answer often decides which route makes sense for you.

Adding prescription drug coverage

If you choose Original Medicare, you must decide separately whether to add Part D (prescription drug coverage). You do this at the same time you enroll in Parts A and B. If you choose Medicare Advantage, most plans include Part D automatically, though a few do not — check the plan details.

Part D is optional, but if you do not sign up when you first become may be able to access and you go without coverage for more than 63 days, you will pay a penalty for as long as you have Medicare. The penalty is about 1% of the national average Part D premium for each month you were without coverage. If you do not take any prescription drugs now, you can still enroll in Part D later without penalty — the penalty only applies if you go without coverage and then enroll later.

Part D plans vary widely in which drugs they cover and how much you pay. If you take regular medications, use the Medicare Plan Finder tool at Medicare.gov to see which plans cover your drugs at the lowest cost. You can also call 1-800-MEDICARE and ask a representative to look up your medications in different plans.

Supplemental insurance (Medigap)

If you choose Original Medicare, you may want to add Medigap (also called Supplemental insurance). Medigap is sold by private insurance companies and covers costs that Original Medicare does not — deductibles, coinsurance, and copays. It is separate from Medicare itself and separate from Part D.

Medigap is optional. Some people find that the extra premium is worth it because they know their out-of-pocket costs are capped. Others prefer to pay less upfront and accept higher costs when they use care. There is no penalty for not buying Medigap, but there is a penalty for buying it late — if you wait more than six months after you enroll in Part B, insurance companies can charge you more or deny you coverage entirely.

You do not need Medigap if you choose Medicare Advantage, because Advantage plans already limit your out-of-pocket costs. In fact, you cannot buy Medigap and Medicare Advantage at the same time.

What happens after you enroll

Once you submit your enrollment, Medicare will send you a confirmation letter in the mail within two weeks. 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. For example, if you turn 65 on June 15 and enroll on May 20, your coverage starts June 1. If you turn 65 on June 15 and enroll on July 10, your coverage starts August 1.

Medicare will mail you a Medicare card before your coverage starts. Do not wait for the card to start using your benefits — your coverage is active even if the card has not arrived. If you need to see a doctor before the card comes, tell the office your Social Security number and birth date, and they can look up your Medicare information.

If you enrolled in a Medicare Advantage plan or Part D, your insurance company will also send you a welcome packet with your plan details, pharmacy network, and doctor network. Read this carefully and call the plan's customer service number if you have questions before your coverage starts.

Special situations: still working, losing employer coverage, or on disability

If you are still working and your employer has 20 or more employees, you can delay enrolling in Medicare Part B without penalty as long as you have health insurance through your job. You must enroll within eight months after your employment or employer coverage ends, or you will pay a penalty. Tell your employer's benefits office that you are turning 65 so they know not to drop you from their plan.

If you are losing employer coverage — through retirement, job loss, or COBRA expiration — you have a special enrollment period. You can enroll in Medicare without penalty for two months after your coverage ends. This gives you time to switch to Medicare even if you miss your initial enrollment window.

If you are on Social Security Disability Insurance (SSDI) and turn 65, you will be automatically enrolled in Original Medicare Parts A and B. You do not have to do anything, but you should still choose Part D if you take medications, because automatic enrollment does not include it.

Frequently Asked Questions

What if I miss my enrollment window?

You can still enroll after your window closes, but you will pay a penalty. For Part B, the penalty is 10% of the standard premium for each full year you were without coverage. For Part D, it is about 1% of the national average premium per month. These penalties are permanent — you pay them for as long as you have Medicare. You can enroll during the General Enrollment Period (January 1 to March 31 each year), and your coverage will start July 1.

Can I change my mind after I enroll?

Yes, during the Annual Enrollment Period (October 15 to December 7 each year), you can switch between Original Medicare and Medicare Advantage, change your Part D plan, or add or drop Medigap. If you just enrolled and want to change your plan within the first three months, you can also make one change during that time. Outside these windows, changes are limited to people with certain life events (moving, losing coverage, getting married).

Do I have to enroll if I am still working?

No, if your employer has 20 or more employees and you have health insurance through that job, you can delay Medicare enrollment. You must enroll within eight months after you stop working or lose that coverage. If you do not enroll within that window, you will pay a penalty.

How much does Medicare cost?

Costs vary by plan and change each year. Original Medicare Part B has a standard monthly premium (around $165 in 2024, but this changes yearly), plus deductibles and coinsurance when you use care. Medicare Advantage plans often have $0 premiums but charge copays. Part D premiums range from $0 to over $100 per month depending on the plan. Call 1-800-MEDICARE for current costs for plans in your area.

What if I do not have a Social Security number?

You can still enroll in Medicare if you are a U.S. citizen or permanent resident without a Social Security number. You will need to provide your citizenship or immigration status and other identifying information. Call 1-800-MEDICARE to enroll by phone, or visit your local Social Security office in person — online enrollment requires a Social Security number.