Medigap Open Enrollment: Your One-Time Window

The six-month guaranteed-issue window

Your Medigap Open Enrollment Period is a one-time, six-month window that starts the first month you are both 65 or older and enrolled in Part B. During this window you have guaranteed issue: any insurer must sell you any Medigap (Medicare Supplement) policy it offers at its best rate, no matter your health. No medical questions, no denials, no pre-existing-condition waiting periods based on your history. This is the only time most people are guaranteed that kind of access.

Why the timing matters so much

The window is automatic and the clock cannot be paused or restarted. Because it begins when your Part B starts, choosing to delay Part B also delays this window — which is one reason the decision to enroll in or postpone Part B deserves careful thought. If you intend to pair Original Medicare with a supplement, you generally want your Part B, and therefore your Medigap window, to begin when you are ready to buy. Walk through how the dates line up in our Medicare enrollment timeline.

What happens if you miss it

Once your six months pass, in most states insurers can apply medical underwriting. They can review your health history and then charge you more, attach a waiting period, or refuse to sell you a policy at all. People who develop a health condition after their window has closed sometimes find themselves locked into their current coverage because no supplement will take them at a reasonable price. A handful of states offer continuous or annual guaranteed-issue rights, but the protections vary widely and you should not assume your state has them.

It is separate from the Annual Enrollment Period

A common mix-up: the Medigap Open Enrollment Period is not the same as the fall Annual Enrollment Period (AEP), October 15 to December 7. The AEP is a yearly window for switching Medicare Advantage and Part D plans. It does not grant Medigap guaranteed issue, and changing an Advantage plan in the fall does nothing to reopen your one-time Medigap window. They are two different things on two different schedules.

How to make the most of it

Treat this window as a hard deadline. Compare plans and lock in the supplement you want while your access is guaranteed. For a deeper look at the rules and the trade-offs, read The Medigap Open Enrollment Period: why you only get one shot and our overview of Medicare Supplement (Medigap) plans. When you are ready, the rest of the turning 65 hub walks through your full first-year plan.