The Basic Rule: Age 65 and Older, Plus Some Younger People

You are covered by Medicare if you are 65 or older and a U.S. citizen or permanent resident who has lived in the country for at least five years. You do not have to be retired or working — age and residency are what matter.

Some people under 65 also get Medicare. This includes people who have received Social Security Disability Insurance (SSDI) for at least 24 months, people with end-stage renal disease (permanent kidney failure requiring dialysis or transplant), and people with amyotrophic lateral sclerosis (ALS, also called Lou Gehrig's disease). These groups become covered automatically once they meet the time or diagnosis requirement — they do not have to wait until 65.

Key Takeaways

  • You become covered by Medicare automatically at 65 if you are already receiving Social Security, or you must sign up yourself if you are still working.
  • People under 65 on SSDI for 24 months, people with end-stage renal disease, and people with ALS also receive Medicare coverage.
  • Permanent residents must have lived in the United States for at least five years to be covered, and citizenship or green card status must be current.
  • If you do not sign up during your initial enrollment window around your 65th birthday, you may pay a higher premium for the rest of your life.

Automatic Enrollment at 65 If You Receive Social Security

If you are already collecting Social Security when you turn 65, Medicare enrollment happens automatically. You will receive your Medicare card in the mail about two weeks before your 65th birthday. You do not need to do anything — the Social Security Administration tells Medicare about you, and the coverage begins on the first day of the month you turn 65.

This automatic enrollment covers Medicare Part A (hospital insurance) and Medicare Part B (medical insurance). You will still need to decide whether to add prescription drug coverage (Part D) or a Medigap or Medicare Advantage plan, but the basic coverage starts without any action on your part.

Signing Up Yourself If You Are Still Working at 65

If you are still working and have not yet claimed Social Security, you must sign up for Medicare yourself. Your initial enrollment window opens three months before the month you turn 65 and closes three months after. For example, if you turn 65 in June, you can sign up from March through September.

You can sign up online at Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office. You will need your birth certificate, proof of citizenship or permanent resident status, and proof of income. If you miss this window and do not have employer coverage, you will pay a penalty on your Part B premium for as long as you have Medicare — usually 10 percent more per year of delay.

People Under 65 Who may have access to Through Disability or Illness

If you receive SSDI, you become covered by Medicare automatically after you have been on SSDI for 24 months. The 24-month waiting period begins the month your disability payments start, not the month you applied. You will receive your Medicare card automatically — no sign-up needed.

If you have end-stage renal disease, you can sign up for Medicare as soon as your doctor determines you need dialysis or a transplant, even if you are not yet on dialysis. If you have ALS, you become covered when ready upon diagnosis — there is no waiting period. For both conditions, you will need to contact Social Security or Medicare directly to enroll, since these do not happen automatically the way SSDI coverage does.

Permanent Residents and Citizenship Requirements

You must be a U.S. citizen or a lawful permanent resident (green card holder) to receive Medicare. If you are a permanent resident, you must have lived in the United States for at least five consecutive years. Time spent outside the country can break the five-year requirement, so if you travel or move abroad, the clock may restart.

If you are a permanent resident and turn 65, you will need to show your green card and proof of five years of U.S. residence when you sign up. If you are not yet a citizen or permanent resident, you are not covered by Medicare, even if you have worked and paid Medicare taxes for many years. Some states offer coverage to immigrants through Medicaid, but that is a separate program.

What Happens If You Miss Your Enrollment Window

If you turn 65 and do not sign up for Medicare Part B during your initial enrollment window, you can still sign up later during the general enrollment period, which runs from January 1 to March 31 each year. However, your coverage will not start until July 1 of that year — a gap of several months.

More importantly, you will pay a penalty. Your Part B premium increases by 10 percent for each full year you were may be able to access but not enrolled. If you delayed for three years, you pay 30 percent more every month for the rest of your life. The only way to avoid this penalty is to have had creditable coverage (such as employer health insurance) during the time you were not on Medicare.

Spouse and Family Coverage

Medicare does not cover spouses or family members based on your coverage. Each person must meet the age or disability requirement on their own. If your spouse is 62 and you are 65, your spouse is not covered by your Medicare — they must wait until they turn 65 or meet another coverage requirement.

If your spouse is also 65 or older, they sign up for their own Medicare during their own initial enrollment window. If your spouse is under 65 and has a disability, they can sign up for Medicare through SSDI or another may have access to condition, but again, this is independent of your coverage.

Frequently Asked Questions

Do I have to be a U.S. citizen to get Medicare?

No. Lawful permanent residents (green card holders) are also covered if they have lived in the United States for at least five consecutive years. You must have current immigration status — expired green cards do not count.

What if I am 65 but still working and have health insurance through my job?

You should still sign up for Medicare Part A (hospital insurance) during your initial enrollment window, even if you keep your employer plan. Part A has no premium if you or your spouse paid Medicare taxes for 10 years. Delaying Part B is usually fine if your employer has 20 or more employees, but you will owe a penalty if you delay Part B after your employer coverage ends.

Can I get Medicare if I have never worked?

Yes, if you are 65 or older and a U.S. citizen or permanent resident. You do not have to have worked or paid Medicare taxes. However, your Part A coverage may have a premium if you or your spouse did not work for at least 10 years.

When does Medicare start if I sign up at 65?

If you sign up during your initial enrollment window (three months before to three months after your 65th birthday), coverage begins on the first day of the month you turn 65. If you sign up during the general enrollment period (January 1 to March 31), coverage starts July 1 of that year.

What if I am on disability but under 24 months on SSDI?

You are not yet covered by Medicare. Once you have been on SSDI for 24 months, Medicare begins automatically. You can check your SSDI status online at ssa.gov or call Social Security at 1-800-772-1213 to confirm when your 24-month period ends.