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What is the Medicare Initial Enrollment Period?

It is the seven month window around your 65th birthday. Sign up in the three months before your birthday month and your coverage starts with no gap.

Updated September 3, 2026 · 3 min read · by Gerino Alejos

Your Initial Enrollment Period is the seven month window built around your 65th birthday. It is the first and cleanest chance you get to join Medicare. When you sign up inside it decides when your coverage starts.

How the seven months are counted

• The three months before your birthday month.
• Your birthday month.
• The three months after your birthday month.

So if you turn 65 in June, your window runs March 1 through September 30.

Why the three months before your birthday matter most

Sign up during the three months before your birthday month and your coverage begins on the first day of your birthday month. You are covered from the day you become eligible, with no gap.

Sign up during your birthday month or in the three months after, and coverage begins on the first day of the month after you sign up. In the meantime you are eligible but not covered.

The first of the month birthday rule

If your birthday falls on the first day of a month, Medicare treats you as turning 65 in the month before. Your whole seven month window moves back by one month.

It is a small rule that moves every date on your calendar. Check it if you were born on the first.

What you can do during this window

• Sign up for Part A, the hospital part, and Part B, the part that pays for doctor visits and outpatient care.
• Join a Medicare Advantage plan, a private plan that delivers your Medicare benefits. See what an Advantage plan is.
• Join a standalone Part D drug plan, a separate plan that only covers prescriptions.
• Buy a Medicare Supplement policy with no health questions asked.

That last one deserves attention. A Medicare Supplement, also called Medigap, pays the share of the bill that Medicare leaves to you. Your Medigap open enrollment runs six months from when Part B begins. During it, no company in Texas can turn you down or charge you more for your health history. That protection does not come back. Read all the enrollment windows to see how they overlap, and why that six month window matters more than any other.

Choosing between the two paths, a supplement or an Advantage plan, is the real work of this window. Talk it through with a licensed agent. Enter your ZIP code and we call you back.

If you are still working

You may be able to skip this window with no penalty, but only if your coverage from work qualifies. The number of employees at your company decides it. Read the rules for working past 65 before you let the window close.

What to do, in order

1. Count back three months from your birthday month and put that date on a calendar now.
2. Decide before that date whether you want the supplement path or the Advantage path, because your Medigap protection runs on its own clock.
3. Apply for Part A and Part B through Social Security. It takes about 15 minutes.
4. Choose your drug coverage or your Advantage plan in the same sitting, not months later.

The application is short. The decision underneath it is the part worth talking through with someone. Call our McAllen office at (956) 687 3334, or enter your ZIP code in the plan pricing box on this page.

Gerino Alejos

Licensed insurance agent · License 3128710 · NPN 18243381

Owner of McAllen Insurance Group, an independent agency on North 10th Street in McAllen. Works with clients across Hidalgo, Cameron and Starr counties on Medicare, Marketplace health, life and auto coverage. Se habla español.