Medicare Initial Enrollment Period

Your Medicare initial enrollment period lasts seven months. It begins three months before the month you turn 65, includes your birth month and extends three months after that. You may be automatically enrolled in Medicare Part A and B if you already receive Social Security benefits.

Rachel Christian, writer and researcher for RetireGuide
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APA Christian, R. (2022, April 21). Medicare Initial Enrollment Period. Retrieved May 19, 2022, from

MLA Christian, Rachel. "Medicare Initial Enrollment Period.", 21 Apr 2022,

Chicago Christian, Rachel. "Medicare Initial Enrollment Period." Last modified April 21, 2022.

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What Is the Initial Enrollment Period for Medicare?

The initial enrollment period is the first time you are eligible to sign up for Medicare.

You can join Medicare Part A and Part B during this time, or select a Medicare Advantage (Part C) plan.

The Medicare initial enrollment period lasts seven months and it:
  • Begins three months before your birthday month.
  • Includes the month you turn 65.
  • Ends three months after your birthday month.

Social Security will mail you sign-up instructions when your initial enrollment period begins. You must enroll in Medicare through the Social Security Administration.

After enrolling, you will receive your Medicare benefits through the U.S. Centers for Medicare & Medicaid Services.

If you already receive Social Security benefits, the Social Security Administration will automatically enroll you at age 65 for Original Medicare (Part A and Part B).

After your initial enrollment period, there are specific times each year when you can change Medicare plans, known as open enrollment periods.

Terry Turner, senior financial writer and financial wellness facilitator, explains the initial enrollment period for Medicare.

When Does Medicare Coverage Begin?

The start of your Original Medicare coverage depends on when you sign up during the initial enrollment period.

When Does Medicare Part A and Part B Coverage Begin?
If You Sign UpCoverage Begins
Three months before your 65th birthdayThe first day of your birthday month
During your birthday monthThe first day of the month after your birthday month
The month after your birthdayThree months after your birth month
Two months after your birth monthFive months after your birth month
Three months after your birth monthSix months after your birth month

Keep in mind that if you miss your initial enrollment period and try to sign up for Medicare later, your coverage may be delayed and cost more money.

However, if you’re still working at 65 and have health insurance through your employer, you may be able to delay Medicare enrollment without this penalty.

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When Can You Sign up for Medicare Advantage or Part D?

If you want to enroll in a Medicare Advantage plan (Part C) — an alternative to Original Medicare that is administered by private companies — you must sign up on your own.

The same applies for Medicare Part D prescription drug coverage.

When You Can Sign Up for Medicare Advantage or Part D
You’re Turning 65
You can enroll during the seven-month window that begins three months before you turn 65, includes your birth month and extends three months after that. If you sign up for a Medicare Advantage plan during this time, you can drop it at any point during the following 12 months and return to Original Medicare.
You Have a Disability and Are Under 65
Your Medicare coverage begins 24 months after you first start receiving Social Security disability benefits or Railroad Retirement Board disability benefits. Your sign-up time extends through the 28th month after you first begin receiving disability benefits.
You Have a Disability and You Turn 65
During this time, you can sign up for a Medicare Advantage or Part D plan. If you already have a Part C or Part D plan, you can switch to a different one. You have a seven-month period to do so. It begins three months before you turn 65, includes your birth month and extends three months after that.

Enrollment in a Medicare Supplement Plan

There are different rules for enrolling in a supplemental insurance plan, also known as Medigap.

According to Centers for Medicare & Medicaid Services, the best time to buy a Medigap policy is the first six months after the month you turn 65.

For example, if you turn 65 in June and enroll in Part B the same month, you should buy a Medigap policy between June and November.

You must be enrolled in Medicare Part B to sign up for a Medigap policy.

John Clark, licensed insurance advisor and owner of Senior Solutions Insurance Agency, explains why you should sign up for a Medicare Supplement plan during the initial enrollment period.

After this six-month window, your Medigap options may be limited and policies may cost more.

Keep in mind that some states may have additional Medigap policy open enrollment periods.

Last Modified: April 21, 2022

6 Cited Research Articles

  1. AARP. (2020, March 25). Do I have to enroll in Medicare at age 65 if I am already collecting Social Security? Retrieved from
  2. (2019, September). Understanding Medicare Advantage & Prescription Drug Plan Enrollment Periods. Retrieved from
  3. (n.d.). Part A & Part B sign up periods. Retrieved from
  4. (n.d.). When can I buy Medigap? Retrieved from
  5. (n.d.). When will my coverage start? Retrieved from
  6. Social Security Administration. (n.d.). Medicare Benefits. Retrieved from