Medigap (Medicare Supplement Insurance)
Medigap is Medicare Supplement Insurance sold by private companies that helps pay some of the health care costs Original Medicare does not cover — like copayments, coinsurance, and deductibles. Medigap works only with Original Medicare, not with Medicare Advantage.
What it means
- Medigap policies are standardized (Plans A, B, C, D, F, G, K, L, M, N) so the same lettered plan covers the same benefits, regardless of the insurer. - You must have both Part A and Part B to buy a Medigap policy, and you pay the insurer a monthly premium in addition to your Part B premium. - The best time to buy Medigap is during your one-time 6-month Medigap Open Enrollment Period, which begins the first month you have Part B and are 65 or older. During this window insurers cannot deny coverage or charge more due to health. - Outside that window, in most states insurers can use medical underwriting.
Action steps
1. Enroll in Part B first — your Medigap Open Enrollment Period starts the month Part B begins. 2. Compare the standardized letter plans at medicare.gov/medigap-supplemental-insurance-plans to see which benefits matter to you. 3. Get quotes from multiple insurers for the same lettered plan; benefits are identical, but premiums vary. 4. Buy during your 6-month Open Enrollment window to lock in guaranteed-issue protections.
Deadlines
- Medigap Open Enrollment Period: the 6-month window that starts the first month you are both 65+ and enrolled in Part B.
Answers in this topic
Questions
- Can I be denied Medigap coverage?
- During your 6-month Medigap Open Enrollment Period, insurers cannot deny you or charge more due to health. Outside that window (and outside a guaranteed-issue right), most states allow medical underwriting.
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Last verified: 2026-07-18