When and how you enroll in Medicare depends on whether you're turning 65 or becoming may be able to access due to disability or end-stage renal disease

Most people become may be able to access for Medicare at 65. You do not automatically get Medicare on your birthday — you must take action during your enrollment window. The timing matters because late enrollment can cost you more in premiums for the rest of your life.

If you are already receiving Social Security benefits when you turn 65, Medicare Part A and Part B will be enrolled automatically. If you are not yet receiving Social Security, you must enroll yourself. People who become may be able to access before 65 due to disability or end-stage renal disease follow a different timeline.

You can enroll online through Medicare.gov, by phone, by mail, or in person at a Social Security office. The method you choose does not change your coverage date — what matters is when you submit your enrollment.

Key Takeaways

  • Your Initial Enrollment Period is the seven-month window that includes your 65th birthday month, three months before, and three months after — missing this window can trigger permanent premium penalties.
  • If you are still working and have health insurance through your employer, you may be able to delay Part B enrollment without penalty if your employer has 20 or more employees.
  • You can enroll online at Medicare.gov, by calling 1-800-MEDICARE, by mail using the enrollment form, or at your local Social Security office.
  • People approved for Social Security Disability Insurance (SSDI) are automatically enrolled in Medicare after 24 months of receiving disability payments.
  • Changing your mind after enrollment is possible during the Annual Enrollment Period (October 15 to December 7 each year) or if you have a may have access to life event.

Your Initial Enrollment Period and why it matters

Your Initial Enrollment Period is a seven-month window: three months before the month you turn 65, the month you turn 65, and three months after. If your birthday is March 15, your window runs from December through June. You can enroll at any point during this window, and your coverage will begin on the first day of your birth month or the first day of the month after you enroll, whichever is later.

If you miss your Initial Enrollment Period, you will pay a permanent 10% increase to your Part B premium for as long as you have Medicare. This penalty is added to your monthly bill and does not go away. The only exception is if you had creditable coverage (health insurance through an employer or union) and did not need Medicare during that time. You must prove you had that coverage when you eventually enroll.

People who become may be able to access for Medicare before 65 due to disability have a different window: they can enroll three months before they become may be able to access, the month they become may be able to access, and three months after.

Enrolling if you are already receiving Social Security

If you are already collecting Social Security retirement or disability benefits when you turn 65, Social Security will automatically enroll you in Medicare Part A and Part B about three months before your 65th birthday. You will receive a Medicare card in the mail. You do not need to do anything.

You will still need to make a choice about Part D (prescription drug coverage) and Medigap or Medicare Advantage if you want that coverage. Part D has its own enrollment important date: you must enroll during your Initial Enrollment Period or during the Annual Enrollment Period (October 15 to December 7), or you will pay a permanent penalty on your Part D premiums. Medigap and Medicare Advantage have different rules — Medigap has a six-month open enrollment period after you turn 65 and enroll in Part B, while Medicare Advantage can be changed during the Annual Enrollment Period.

Enrolling if you are not yet receiving Social Security

If you are not receiving Social Security when you turn 65, you must enroll in Medicare yourself. You can do this online, by phone, by mail, or in person. Start the process at least two months before your 65th birthday to make sure your coverage begins on time.

Online: Go to Medicare.gov and click "Sign up for Medicare." You will need your Social Security number and birth date. The online process takes about 10 minutes. You can upload documents or mail them later if needed.

By phone: Call 1-800-MEDICARE (1-800-633-4227). Representatives are available Monday through Friday, 8 a.m. to 8 p.m. Eastern time, and Saturday 9 a.m. to 1 p.m. Eastern time. Have your Social Security number and birth date ready. The call takes about 15 minutes.

By mail: read the "process for Enrollment in Part A and/or Part B" (form CMS-40B) from Medicare.gov. Fill it out, sign it, and mail it to your local Social Security office. Mail enrollment takes two to four weeks, so send it early.

In person: Visit your local Social Security office. Bring your Social Security card, birth certificate, and proof of citizenship or legal residency. You can find your office at ssa.gov/locator.

If you are still working and have employer health insurance

If you are still working at 65 and your employer has 20 or more employees, you may be able to delay Part B enrollment without paying a penalty. This is called the Special Enrollment Period for people with group health plan coverage. You must enroll in Part A (hospital insurance) at 65, but you can wait to enroll in Part B until you leave your job or your employer coverage ends.

When you do enroll in Part B, you have eight months from the date your employer coverage ends to sign up without penalty. If you wait longer than eight months, you will pay the 10% permanent premium increase for each year you delayed.

To use this exception, your employer coverage must be based on your current employment — coverage you had before you retired does not count. You will need to show proof of your employer coverage when you enroll in Part B. Your employer's human resources department can provide a letter stating the coverage dates and number of employees.

Automatic enrollment for people on disability

If you receive Social Security Disability Insurance (SSDI), you will be automatically enrolled in Medicare Part A and Part B after you have been receiving disability payments for 24 months. You do not need to explore or take any action. Medicare will begin on the 25th month of your disability payments.

You will receive your Medicare card in the mail about three months before your coverage begins. Like people turning 65, you will still need to choose Part D coverage and decide whether you want Medigap or Medicare Advantage.

If you have end-stage renal disease (ESRD) or ALS (amyotrophic lateral sclerosis), you become may be able to access for Medicare when ready, not after a waiting period. You should enroll as soon as you receive your diagnosis.

Choosing your coverage after enrollment

Enrolling in Medicare Part A and Part B is only the first step. You also need to decide about prescription drug coverage (Part D) and supplemental coverage (either Medigap or Medicare Advantage). These choices have their own enrollment important date and rules.

Part D (prescription drugs): You must enroll during your Initial Enrollment Period or during the Annual Enrollment Period (October 15 to December 7). If you do not enroll when you are first may be able to access and you go without Part D coverage, you will pay a permanent penalty on your Part D premiums when you eventually enroll. The penalty is about 1% of the national average Part D premium for each month you were without coverage.

Medigap: You have a six-month open enrollment period starting the month you turn 65 and enroll in Part B. During this time, insurance companies cannot deny you coverage or charge you more based on your health. After this period ends, you may face medical underwriting and higher premiums.

Medicare Advantage: You can enroll during your Initial Enrollment Period or during the Annual Enrollment Period. If you choose Medicare Advantage and later want to switch to Original Medicare and Medigap, you have limited windows to do so without facing underwriting.

What to do if you miss your enrollment important date

If you miss your Initial Enrollment Period, you can still enroll, but you will pay a permanent 10% increase to your Part B premium. The only way to avoid this penalty is to prove you had creditable coverage (employer or union health insurance) during the time you were not enrolled in Medicare.

You can enroll during the General Enrollment Period, which runs January 1 to March 31 each year. Your coverage will begin July 1. This is slower than enrolling during your Initial Enrollment Period, when coverage can begin as early as the first of your birth month.

If you had a may have access to life event — such as loss of employer coverage, divorce, or death of a spouse — you may have a Special Enrollment Period that allows you to enroll without penalty. You must report the life event to Medicare within 60 days. Call 1-800-MEDICARE to report it.

Frequently Asked Questions

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

You must enroll in Part A at 65 even if you are still working. However, if your employer has 20 or more employees and you have health insurance through that employer, you can delay Part B enrollment without penalty. When your employment ends or your coverage stops, you have eight months to enroll in Part B without penalty.

What happens if I enroll late?

If you enroll after your Initial Enrollment Period ends, you will pay a permanent 10% increase to your Part B premium for as long as you have Medicare. This penalty does not expire. The only exception is if you had credible employer or union coverage during the time you were not enrolled.

Can I change my mind after I enroll?

Yes. You can make changes during the Annual Enrollment Period (October 15 to December 7 each year). If you have a may have access to life event such as loss of coverage or a move, you may have a Special Enrollment Period outside the annual window. Call 1-800-MEDICARE to report a life event.

How long does it take to get my Medicare card after I enroll?

If you enroll online or by phone, you will receive your card in the mail within two to four weeks. If you enroll by mail, allow four to six weeks. If you need coverage to start sooner, you can use your enrollment confirmation number as proof of coverage until your card arrives.

What if I'm not a U.S. citizen?

You must be a U.S. citizen or a lawful permanent resident who has lived in the United States for at least five years to enroll in Medicare. When you enroll, you will need to provide proof of citizenship or legal residency, such as a passport, birth certificate, or green card.