Medicare begins the month you turn 65, but only if you have signed up on time

If you are a U.S. citizen or permanent resident, Medicare Part A (hospital insurance) and Part B (medical insurance) coverage starts on the first day of the month in which you turn 65. You do not have to wait until your birthday itself — the coverage date is automatic for that entire month. However, this only happens if you have already signed up, or if you are already receiving Social Security or Railroad Retirement Board benefits. If you have not signed up and are not yet collecting benefits, you will need to take action before your 65th birthday to avoid a gap in coverage and a permanent penalty on your Part B premiums.

The rules are different for Part D (prescription drug coverage) and Medigap or Medicare Advantage plans. Part D has its own enrollment window, and missing it carries a lifelong penalty. Medigap and Medicare Advantage plans have limited times when you can sign up without being turned down for pre-existing conditions. Understanding these separate timelines is the difference between smooth coverage and unexpected costs or gaps.

Key Takeaways

  • Part A and Part B coverage begins the first day of the month you turn 65 if you have already signed up or are receiving Social Security benefits.
  • If you are not yet receiving Social Security, you must sign up for Medicare during your Initial Enrollment Period — the three months before, the month of, and the three months after your 65th birthday — to avoid a permanent 10 percent penalty on Part B premiums.
  • Part D (prescription drug coverage) has its own enrollment window and carries a separate lifetime penalty if you miss it and go without creditable drug coverage.
  • Medigap and Medicare Advantage plans can only be purchased during certain windows; outside those windows, insurers can deny you or charge more based on health conditions.
  • You can sign up for Medicare through Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.

What happens if you are already receiving Social Security

If you are already collecting Social Security retirement or disability benefits when you turn 65, you do not need to do anything. Medicare Part A and Part B will start automatically on the first day of the month you turn 65. You will receive a Medicare card in the mail about two weeks before your coverage begins. This automatic enrollment applies whether you started Social Security at 62, at your full retirement age, or at 70.

Even though enrollment is automatic, you should still review your Medicare card when it arrives to make sure the information is correct. Check your name, date of birth, and Social Security number. If anything is wrong, contact Social Security at 1-800-772-1213 to correct it before your coverage starts.

What happens if you are not yet receiving Social Security

If you are not collecting Social Security benefits, you must sign up for Medicare yourself during your Initial Enrollment Period. This window runs for seven months: the three months before you turn 65, the month you turn 65, and the three months after. For example, if you turn 65 in June, your enrollment period runs from March through September.

During this window, you can sign up for Part A and Part B without any penalty, and you can choose a Medigap or Medicare Advantage plan without being turned down for pre-existing conditions. If you miss this window and do not sign up within three months after it closes, you will face a permanent 10 percent increase on your Part B premiums for as long as you have Medicare. This penalty is added to your monthly premium and never goes away, even if you sign up later.

You can sign up through Medicare.gov, by calling 1-800-MEDICARE, or by visiting your local Social Security office in person. The Social Security office is often the fastest route if you need to sign up quickly, because staff can process your enrollment on the spot.

Part D enrollment and the prescription drug important date

Part D (prescription drug coverage) has its own enrollment rules separate from Part A and Part B. You can sign up for Part D during your Initial Enrollment Period at the same time you sign up for Part A and Part B, or you can wait and sign up during the Annual Enrollment Period (October 15 through December 7 each year). However, if you go without creditable drug coverage — meaning coverage that is at least as good as Medicare's standard Part D plan — you will face a permanent penalty.

The penalty is 1 percent of the national average Part D premium for each month you were without coverage. If you delay signing up for Part D by two years, for example, your penalty will be roughly 24 percent of the average premium, and that penalty stays with you for life. Even if you eventually sign up, you will pay the higher amount every month. The only way to avoid this penalty is to have creditable coverage from another source — such as an employer plan or a union plan — during the time you are not enrolled in Part D.

You can enroll in Part D through Medicare.gov, through individual insurance company websites, or by calling 1-800-MEDICARE. It is worth comparing plans each year during the Annual Enrollment Period, because premiums and covered drugs change.

Medigap and Medicare Advantage timing

Medigap (supplemental insurance) and Medicare Advantage (an alternative to Original Medicare) have different enrollment rules than Part A and Part B. You have the strongest protections during your Medigap Open Enrollment Period, which is the six months after you turn 65 and sign up for Part B. During this window, insurance companies cannot turn you down or charge you more because of pre-existing conditions. After this period ends, insurers can deny your process or charge higher premiums based on your health history.

Medicare Advantage plans can be purchased during the Initial Enrollment Period (the seven-month window around your 65th birthday) or during the Annual Enrollment Period each fall. If you miss both windows, you can only switch to a different Medicare Advantage plan or to Original Medicare during the Annual Enrollment Period, and only if you already have a Medicare Advantage plan. If you have Original Medicare and miss the enrollment windows, you cannot switch to Medicare Advantage until the next Annual Enrollment Period.

What to do in the months before you turn 65

Start planning three months before your 65th birthday. Gather your documents: your Social Security number, proof of citizenship or permanent residency, and information about any current health insurance you have. If you are still working and have employer coverage, find out whether that coverage is creditable for Part D purposes — your employer's benefits office can tell you.

Visit Medicare.gov and use the Plan Finder tool to see what Part D plans, Medigap plans, and Medicare Advantage plans are available in your area. Costs and covered drugs vary widely by plan and by year, so comparing options now will save you money. If you need help understanding your choices, you can contact your State Health Insurance information Program (SHIP), which offers free counseling. Find your state's SHIP by calling 1-877-839-2675 or visiting shiptalk.org.

If you are not yet receiving Social Security, decide whether you will sign up for Social Security at the same time you enroll in Medicare, or whether you will delay Social Security and enroll in Medicare only. These are separate decisions, and you can make them independently. However, if you are working and earning above a certain amount, delaying Social Security may make sense for you — a financial advisor or your local Social Security office can help you think through the trade-offs.

Coverage gaps and what they cost

Missing your enrollment important date does not mean you lose coverage forever, but it does mean you will pay more. If you miss your Initial Enrollment Period for Part A and Part B, you can still sign up during the General Enrollment Period (January 1 through March 31 each year), but your coverage will not start until July 1 of that year. You will also face a permanent 10 percent penalty on Part B premiums.

If you miss the Part D enrollment important date, you can sign up during the Annual Enrollment Period, but you will pay the lifetime penalty. If you miss both the Initial Enrollment Period and the General Enrollment Period for Part A and Part B, you may have a gap in coverage. During that gap, you are responsible for all hospital and medical costs. If you have employer coverage, that coverage may bridge the gap, but do not assume it will — check with your employer's benefits office.

Frequently Asked Questions

Does Medicare start on my birthday or on the first of the month?

Medicare starts on the first day of the month you turn 65, not on your birthday itself. If you turn 65 on June 15, your coverage begins June 1. If you turn 65 on July 1, your coverage begins July 1.

What if I am still working at 65 — do I have to sign up for Medicare?

If you are still working and have employer coverage, you can delay signing up for Part B without penalty as long as your employer has 20 or more employees. You must sign up within eight months after your employment or coverage ends, or you will face a permanent penalty. Part A has different rules — you can delay it without penalty only in certain situations. Contact Medicare at 1-800-MEDICARE to confirm your specific situation.

Can I change my mind after I sign up for a Medicare plan?

Yes, but only during certain windows. You can switch plans during the Annual Enrollment Period (October 15 through December 7) or during the Medicare Advantage Open Enrollment Period (January 1 through March 31 if you are already in a Medicare Advantage plan). Outside these windows, you are locked into your choice unless you have a may have access to life event such as moving, losing coverage, or getting married.

What if I turn 65 while living outside the United States?

You can still sign up for Medicare, but Part B coverage may be limited outside the U.S. Part A covers inpatient hospital care in U.S. territories and some situations abroad. Part B generally does not cover care outside the U.S. Contact Medicare at 1-800-MEDICARE before your 65th birthday to discuss your situation and any supplemental coverage you might need.

Do I need to do anything if I am on Medicare Disability and turn 65?

No. Your Medicare coverage automatically converts from disability-based to age-based on the first day of the month you turn 65. Your coverage continues without interruption, and your Medicare card will be updated automatically. You do not need to sign up again.