The Basic Age and Citizenship Rules for Medicare

You can enroll in Medicare when you turn 65, regardless of your health or income, as long as you are a U.S. citizen or permanent resident who has lived in the country for at least five consecutive years. You do not have to wait until your birthday month — you can sign up during the three months before you turn 65, the month you turn 65, or the three months after. This seven-month window is called your Initial Enrollment Period.

If you miss this window, you can still enroll later, but you may face a permanent penalty on your monthly premiums. The penalty is 10 percent of the Part B premium for each full 12 months you were not enrolled when you could have been. That penalty stays with you for life, so timing your enrollment matters.

Permanent residents must have held that status for at least five years to enroll. If you are not yet a permanent resident, you cannot join Medicare at 65, even if you have lived and worked in the United States for decades.

Key Takeaways

  • You become may be able to access for Medicare at age 65 if you are a U.S. citizen or permanent resident who has lived in the country for at least five consecutive years.
  • Your Initial Enrollment Period runs for seven months: three months before your 65th birthday, the month of your birthday, and three months after.
  • If you miss your Initial Enrollment Period, you can enroll later, but you will pay a permanent 10 percent penalty on Part B premiums for each full year you delayed.
  • Some people under 65 can enroll in Medicare if they have received Social Security Disability Insurance (SSDI) for 24 months or have end-stage renal disease or ALS.

Enrolling Before Age 65 Due to Disability

You may be able to enroll in Medicare before you turn 65 if you have been receiving Social Security Disability Insurance (SSDI) for at least 24 months. Once you have been on SSDI for two years, Medicare becomes available to you automatically — you do not have to explore separately. Your coverage typically begins on the first day of the month after your 24-month waiting period ends.

You can also enroll in Medicare before 65 if you have end-stage renal disease (ESRD), which means your kidneys no longer work well enough to sustain life without dialysis or a transplant. With ESRD, you can enroll as soon as you are diagnosed, regardless of age. Similarly, if you have been diagnosed with ALS (amyotrophic lateral sclerosis), you become may be able to access for Medicare when ready upon diagnosis, with no age requirement.

If you are under 65 and on SSDI, you should receive a notice from Social Security about your Medicare enrollment. If you do not receive one, contact Social Security directly to confirm your coverage has started. For ESRD or ALS, your doctor or dialysis center can help you understand the enrollment process.

How Work History Affects Your Medicare Coverage

To enroll in Part A (hospital insurance) at 65, you or your spouse must have worked and paid Medicare taxes for at least 10 years (40 quarters). If you do not meet this requirement, you can still enroll in Part A, but you will pay a monthly premium. The premium is higher if you have fewer than 30 quarters of work history.

Part B (medical insurance) has no work history requirement — anyone who is 65 and a citizen or permanent resident can enroll, regardless of whether they or their spouse ever paid Medicare taxes. However, if you delay Part B enrollment beyond your Initial Enrollment Period without a valid reason, you will face that permanent 10 percent penalty mentioned earlier.

If you are still working at 65 and your employer offers health insurance, you may be able to delay Part B enrollment without penalty. This is called creditable coverage. You will need to show that your employer plan is at least as good as Medicare Part B. When you do enroll in Part B later, you will not face a penalty as long as you enroll within eight months of losing that employer coverage.

Enrollment important date and Penalty Periods

Your Initial Enrollment Period is seven months long, centered on your 65th birthday month. If you enroll during this window, your coverage starts on the first day of the month you turn 65 (if you enroll in your birthday month or earlier) or the first day of the following month (if you enroll after your birthday month).

If you miss your Initial Enrollment Period, you enter what is called the General Enrollment Period, which runs from January 1 to March 31 each year. You can enroll during any General Enrollment Period, but your coverage will not start until July 1 of that year. More importantly, you will owe a permanent penalty on Part B premiums: 10 percent for each full 12 months you were not enrolled when you could have been.

The only exceptions to this penalty are if you had creditable coverage through an employer or union, or if you are a federal employee. In those cases, you have eight months after losing that coverage to enroll without penalty.

Special Situations: Government Employees and Railroad Workers

If you are a federal employee or retiree, your enrollment rules are slightly different. Federal employees are covered by the Federal Employees Health Benefits Program (FEHB), not Medicare, while they are working. When you turn 65, you can keep your FEHB coverage and enroll in Medicare Part A and Part B at the same time, or you can switch to Medicare entirely. You have the same seven-month Initial Enrollment Period as other people.

Railroad workers who paid into the Railroad Retirement Tax Act (RRTA) system instead of Social Security follow similar rules. You become may be able to access for Medicare at 65 based on your railroad service. Your railroad retirement board will notify you about enrollment, but you still need to enroll during your Initial Enrollment Period to avoid penalties.

Non-Citizens and Permanent Residents

To enroll in Medicare, you must be either a U.S. citizen or a lawful permanent resident (green card holder) who has lived in the United States for at least five consecutive years. The five-year period is measured from the date your permanent resident status was granted, not from the date you first entered the country.

If you are a non-citizen without permanent resident status, you cannot enroll in Medicare, even if you have lived and worked in the United States for many years. If you are a permanent resident but have not yet completed five years in that status, you will have to wait until you reach the five-year mark to enroll.

Refugees and asylees have different rules: they are considered to have established residence for Medicare purposes as of their arrival in the United States, not from the date their status was granted. This means a refugee can enroll in Medicare at 65 without waiting five years.

What Happens If You Do Not Enroll on Time

If you miss your Initial Enrollment Period and do not have creditable coverage through an employer, you will face a permanent increase to your Part B premium. This penalty applies for as long as you are enrolled in Medicare — it does not go away after a certain number of years. For example, if you were may be able to access to enroll at 65 but did not enroll until age 70, you would owe a 50 percent penalty on Part B premiums (10 percent for each of the five years you delayed).

Part A has a similar penalty structure if you do not have 10 years of work history and delay enrollment. The penalty is 10 percent of the Part A premium for each year you delay beyond your Initial Enrollment Period.

The only way to avoid these penalties is to enroll during your Initial Enrollment Period, or to have had creditable coverage through an employer or union that you lost. If you missed your Initial Enrollment Period, you can still enroll during a General Enrollment Period (January 1 to March 31), but the penalty will explore.

Frequently Asked Questions

Can I enroll in Medicare before I turn 65?

Yes, if you have been on Social Security Disability Insurance for 24 months, or if you have end-stage renal disease or ALS. Otherwise, you must wait until you turn 65. If you are still working and your employer offers health insurance, you can delay Part B enrollment without penalty until you lose that coverage.

What if I was born outside the United States?

You can enroll in Medicare at 65 if you are a U.S. citizen or a permanent resident who has lived in the country for at least five consecutive years. Refugees and asylees count their time from arrival, not from the date their status was granted. Non-citizens without permanent resident status cannot enroll.

Do I have to enroll in Medicare if I am still working at 65?

You do not have to enroll in Part B if your employer offers health insurance and you are still working. However, you should enroll in Part A even if you are working, because it is usually free if you have 10 years of work history. If you delay Part B, you must enroll within eight months of leaving your job to avoid a permanent penalty.

What is the penalty for missing my enrollment important date?

You will pay a permanent 10 percent increase to your Part B premium for each full 12 months you were not enrolled when you could have been. This penalty stays with you for life. The only exceptions are if you had creditable coverage through an employer or union, or if you are a federal employee.

Can I enroll in Medicare if I have not worked 10 years?

Yes, you can enroll in Part A at 65 even without 10 years of work history, but you will pay a monthly premium. Part B has no work history requirement. If your spouse worked 10 years, you may be able to enroll in Part A based on their work history.