You get exactly one Medigap open enrollment period: the 6 months starting the month you’re 65 or older and enrolled in Medicare Part B.
During that window, insurers must sell you any Medigap policy they offer, at standard rates, regardless of your health. After it closes, in most states they can decline you or charge more based on medical underwriting.
Unlike Medicare’s annual enrollment, this window never repeats. Here’s how to use it, as of August 2026.
Why does this window matter so much?
Medigap (Medicare Supplement) policies pay the out-of-pocket costs Original Medicare leaves behind — deductibles, the 20% coinsurance, hospital copays. They’re guaranteed renewable for life once issued.
But outside protected windows, Medigap is one of the few corners of health insurance where pre-existing conditions still count. An applicant with diabetes, heart disease, or a cancer history can be denied outright or quoted a much higher premium. During your open enrollment period, none of that applies:
- No health questions can be used against you
- No denial, no rate-up for health
- At most, a waiting period of up to 6 months for pre-existing conditions — and prior "creditable coverage" (like an employer plan) reduces or eliminates even that
When exactly does your window run?
It starts the first month you have both: age 65+ and Part B. Common scenarios:
| Situation | Window |
|---|---|
| Enroll in Part B at 65 | Your 65th-birthday month + 5 more months |
| Worked past 65 with employer coverage, delayed Part B | Starts when Part B finally begins — no penalty for the wait |
| Under 65 on Medicare via disability | No federal window; many states grant one (and you get the regular window at 65) |
The trap: taking Part B at 65 while still on employer coverage burns the window — it runs whether or not you buy Medigap. If you’re working past 65 with group coverage, delaying Part B usually preserves both the window and avoids the Part B late enrollment penalty.
How do you choose during the window?
- Pick the plan letter (standardized nationally, except in a few states): Plan G is the most comprehensive available to new enrollees; Plan N trades small copays for lower premiums. Benefits are identical across insurers for the same letter.
- Compare only price and pricing method among insurers for that letter: community-rated, issue-age-rated, or attained-age-rated policies age very differently in cost.
- Use Medicare.gov’s Medigap finder or your State Health Insurance Assistance Program (SHIP) for local rates — SHIP counseling is free.
Note the fork in the road: Medigap pairs with Original Medicare. If you choose Medicare Advantage instead, you don’t need (and can’t use) Medigap. Switching from Advantage back to Original Medicare later usually means facing Medigap underwriting — another reason this first window is the decision point.
What if you missed the window?
Guaranteed-issue rights still arise in specific situations — your Advantage plan leaves your area, an employer plan ends, a trial right after first joining Advantage, and others. A few states (New York and Connecticut among them) require insurers to accept applicants year-round. Everyone else applies subject to underwriting: you can still be approved, just not guaranteed. If premiums are the obstacle, check whether a Medicare Savings Program route fits instead.
FAQ
Does the window apply per insurer?
No — it’s one clock covering all insurers and all plan letters.
Can I switch Medigap plans later?
Yes, but in most states the new insurer can underwrite you. Buy the plan you actually want the first time.
Is Plan F still available?
Only to those first eligible for Medicare before 2020. New enrollees look at G and N.
Do Medigap plans cover drugs?
No. Pair Medigap with a standalone Part D plan.