Medigap Open Enrollment Period: Guaranteed Issue Rights and Pre-Existing Conditions

The Medigap Open Enrollment Period is the most important window most new Medicare beneficiaries don't fully understand. It's a one-time, 6-month window during which every Medigap insurer must sell you any plan they offer — regardless of your health, medical history, or pre-existing conditions.

Once this window closes, buying a Medigap plan gets significantly harder and potentially more expensive.

When the Window Opens

Your Medigap Open Enrollment Period starts the first month you are both:

1. Enrolled in Medicare Part B, and
2. Age 65 or older

It runs for exactly six months from that date. If your Part B effective date is July 1, your Medigap window runs from July 1 through December 31.

There's no way to reopen this window. Unlike the Annual Enrollment Period for Medicare Advantage and Part D, Medigap Open Enrollment happens once.

What Guaranteed Issue Means

During these six months, insurers are legally required to:

• Sell you any Medigap plan they offer in your state — you pick the plan letter (G, N, etc.), not them
• Charge you the same price as a healthy applicant of the same age in the same area
• Ignore your medical history completely — no health questionnaire, no pre-existing condition exclusions, no denial
• Cover pre-existing conditions immediately or, at most, impose a 6-month waiting period (and only if you didn't have at least 6 months of prior creditable coverage)

After the window closes, most states let insurers use medical underwriting. That means they can ask about your health history, deny coverage, or charge significantly higher premiums based on conditions like diabetes, heart disease, or cancer history.

Guaranteed Issue Rights Outside Open Enrollment

There are limited situations where federal law gives you guaranteed issue rights to buy a Medigap plan outside your initial Open Enrollment Period:

• Your Medicare Advantage plan leaves your area or stops participating in Medicare
• Your Medigap insurer goes bankrupt or commits fraud
• You joined a Medicare Advantage plan when first eligible for Medicare and want to switch back to Original Medicare within the first 12 months
• You lose employer/union coverage that supplemented Medicare

In these situations, you can buy Medigap Plans A, B, C, F, K, or L without medical underwriting (the specific plans available depend on the triggering event). But this is a narrower set of plans than the full menu available during your initial open enrollment.

Pre-Existing Conditions: The Waiting Period Rule

If you buy a Medigap plan during your Open Enrollment Period, the insurer can impose a waiting period of up to 6 months for pre-existing conditions — but only if you had a break in creditable health coverage of 63 days or more in the 6 months before your Medigap policy started.

If you had continuous coverage (employer plan, Medicare Advantage, or another Medigap plan) with no gap exceeding 63 days, the pre-existing condition waiting period is waived entirely. Your Medigap plan covers everything from day one.

This is another reason the transition from employer coverage to Medicare needs to be carefully timed. A gap in coverage doesn't just expose you to medical bills — it can delay your Medigap benefits for pre-existing conditions.

Which Medigap Plans Are Available

Medigap plans are standardized by letter. The most popular options in 2026:

Plan G — the most comprehensive plan available to new enrollees. Covers everything except the annual Part B deductible ($283 in 2026). After you pay that deductible, you have zero out-of-pocket costs for Part B services.

Plan N — lower premiums than Plan G, but you pay up to $20 for some office visits and up to $50 for emergency room visits that don't result in admission. Also requires you to pay the Part B deductible and any Part B excess charges.

Plans C and F are only available to people who became eligible for Medicare before January 1, 2020.

Don't Wait Until You Need It

The biggest mistake is assuming you can buy Medigap later if your health changes. By then, the open enrollment window is closed, and an insurer can deny you coverage entirely based on the very condition that made you want the plan.

The Medicare Enrollment Guide includes the full Medigap plan comparison, state-by-state variations in guaranteed issue rules, and a timeline for coordinating your Medigap purchase with Part B enrollment.

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