By Christian BrinkleyLicensed NC Insurance Agent, NPN 22217190, NC Life & Health · Updated October 14, 2026 · 4 min read
Medigap, also called Medicare Supplement, helps pay costs Original Medicare does not cover. But you cannot buy Medigap on the same terms whenever you want. There is a one time six month window when you have a guaranteed right to buy any Medigap plan sold in your state, no matter your health. Miss it, and buying Medigap gets harder and more expensive.
What Is the Medigap Open Enrollment Period?
Your Medigap Open Enrollment Period starts the first day of the month you turn 65 and are enrolled in Part B. It lasts six months. During this time, insurers must sell you any Medigap plan they offer in your state, even if you have health problems. They cannot charge more because of your health or turn you down.
What Does Guaranteed Issue Mean?
Guaranteed issue means the insurer must sell you the plan.
That limited exception: if you had no prior creditable coverage, the insurer can impose up to a six month waiting period for a pre existing condition. Even then, it must sell you the plan and cover other conditions right away.
Guaranteed issue is the strongest protection you get buying Medigap. It is why the six month window matters so much.
What Is Underwriting?
After your Medigap Open Enrollment Period ends, insurers in most states can use medical underwriting. They can ask about your health, review your medical history, and decide whether to sell you a plan and what to charge.
Guaranteed Issue Rights Outside Open Enrollment
Some situations give you a guaranteed issue right to buy Medigap even after your window ends. Common ones include your Medicare Advantage plan leaving your area, your employer coverage that supplemented Medicare ending, your Medigap insurer going out of business, or using your trial right: joining Medicare Advantage when first eligible and switching back to Original Medicare within the first year.
Standardized Plans
Medigap plans are standardized in most states and labeled by letter: A, B, D, G, K, L, M, and N. Plans C and F are no longer available to people who became eligible for Medicare on or after January 1, 2020.
Common Mistakes
The biggest mistake is waiting too long. People assume they can buy Medigap anytime. They try Medicare Advantage for a few years, then try to switch back and cannot pass underwriting, or the premium is far higher than at 65.
Another mistake is assuming you can switch Medigap plans freely. In most states, switching after the window requires underwriting, even to change companies for the same letter plan.
What to Do During Your Window
If you want Medigap, enroll in Part B to start the clock, then shop. Compare Plan G and Plan N from several companies.
Pick a Part D drug plan at the same time using the Medicare Plan Finder at medicare.gov, based on your actual prescriptions and pharmacy.
Getting Help
Your state SHIP program offers free, unbiased help. In North Carolina, it is called SHIIP. Counselors can explain Medigap plans, compare premiums, and clarify your state rules. You can also call 1-800-MEDICARE or talk to a local licensed insurance agent for quotes from multiple companies.
This article is general information only. It is not personal advice or a recommendation about any specific plan.
Questions people ask me about this
What is the Medigap open enrollment period?
Your Medigap Open Enrollment Period starts the first day of the month you turn 65 and are enrolled in Part B. It lasts six months. During this time, insurers must sell you any Medigap plan they offer in your state, even if you have health problems. They cannot charge more because of your health or turn you down. This window is automatic.
What does guaranteed issue mean?
Guaranteed issue means the insurer must sell you the plan. That limited exception: if you had no prior creditable coverage, the insurer can impose up to a six month waiting period for a pre existing condition. Even then, it must sell you the plan and cover other conditions right away.
What is underwriting?
After your Medigap Open Enrollment Period ends, insurers in most states can use medical underwriting. They can ask about your health, review your medical history, and decide whether to sell you a plan and what to charge.
How does premiums work?
Premiums vary by plan, company, age, and location. Companies use different pricing methods. Community rated plans charge everyone the same regardless of age. Issue age rated plans base the premium on your age when you buy, and it does not rise as you age, though it can rise with inflation.
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