The three enrollment periods for Medicare are initial enrollment, special enrollment, and general enrollment. These are the only times you can sign up for Medicare or make changes to your coverage.

Medicare enrollment periods happen at the same time each year and allow multiple chances to evaluate your healthcare coverage.

Depending on your circumstances, you may need to enroll during a certain enrollment period.

Keep reading to learn more about specific Medicare enrollment periods, including the changes you can make and when your new coverage begins.

In the months before and after your 65th birthday, you have a 7-month initial enrollment period to sign up for Medicare Part A (hospital insurance) and Medicare Part B (medical insurance). This period is open:

  • 3 months before your 65th birthday month
  • the month of your 65th birthday
  • 3 months after your 65th birthday month

For example, if your birthday is August 29, 1959, your initial enrollment period runs from May 1, 2024, through November 30, 2024.

You can also sign up for a Medicare Part D (prescription drug) plan at this time. You can also buy a Medicare supplement (Medigap) plan for additional coverage.

If you miss the 7-month window of your initial enrollment period, you may have an opportunity to sign up for Medicare during a special enrollment period (SEP). You may be eligible for a SEP if:

  • You’re covered under a group health plan through your current employment, which allows you to sign up anytime outside of your initial enrollment period for Medicare parts A or B, or both. You qualify for this SEP if you or your spouse (or, if you have a disability, a family member) is working and, based on that work, you’re covered by a group health plan through the employer.
  • Your employment or the group health plan from that current employment ends, in which case you have an 8-month SEP starting the month following those terminations. COBRA and retiree health plans are not considered coverage based on current employment, so you’re not eligible for a SEP when that coverage ends.
  • You have a health savings account (HSA) with a high-deductible health plan based on your employment or spouse’s. Although you can withdraw money from your HSA after enrolling in Medicare, you should stop contributing to your HSA a minimum of 6 months before applying for Medicare.
  • You’re a volunteer serving in a foreign country, for which you may qualify for a SEP for Medicare Part A or Part B.

Medicare open enrollment is between October 15 and December 7 each year.

During open enrollment, you can change coverage within Medicare. For example, you can:

If you change your Medicare coverage during the annual open enrollment, your old coverage will end, and your new coverage will start on January 1 of the following year.

This means that if you made a change on November 3, 2024, it will take effect on January 1, 2025.

If you sign up for Medicare Part A and Medicare Part B during the first 3 months of your initial enrollment period, your coverage will start on the first day of your birthday month.

  • Example: If your 65th birthday is June 27, 2025, and you sign up for Medicare in March, April, or May 2025, your coverage will begin on June 1, 2025.

If your birthday falls on the first day of the month, your coverage starts on the first day of the month before your birthday month.

  • Example: If your 65th birthday is September 1, 2025, and you sign up for Medicare in May, June, or July 2025, your coverage will begin on August 1, 2025.

If you do not sign up for Medicare parts A and B during your initial enrollment period, here are some examples of when your coverage will start based on when you sign up:

  • If you sign up in the month of your 65th birthday or the 3 months after, your coverage will start 1 month after you sign up.
  • If you sign up more than 6 months after your 65th birthday, Part A coverage will be retroactive for 6 months.

People with certain disabilities can enroll in Medicare, even if they are under 65 years old.

If you are eligible for Medicare because you have amyotrophic lateral sclerosis (ALS), you will be automatically enrolled the first month you receive Social Security disability insurance (SSDI).

If you have end stage renal disease (ESRD), your Medicare coverage usually begins after 3 months of dialysis treatment, though you may have to complete forms to enroll.

If you have another disability and receive Social Security disability insurance (SSDI), you will be automatically enrolled after 25 months.

There are four main Medicare sign-up periods:

  1. Initial enrollment period: a 7-month period beginning 3 months before your 65th birthday month and including your 65th birthday month through 3 months after your 65th birthday month
  2. Special enrollment period: based on circumstances such as an employer-based group health plan or volunteering in a foreign country
  3. General enrollment period: January through March every year for people who missed their initial enrollment period
  4. Open enrollment period: mid-October through early December for people needing to change coverage within Medicare

You can apply for Medicare during one of those windows. Learn what documents you need to apply and how to get started.