Medigap plans are private health insurance policies that help with your Original Medicare costs. Medigaps only work with Original Medicare; not Medicare Advantage plans. If you have a Medigap policy, Original Medicare pays its share of your care first, and then Medigap pays part or all of the remaining costs. Medigaps cover costs such as deductibles, coinsurances, and copayments. Medigaps may also cover some health care that Medicare doesn’t cover at all, such as additional days of inpatient hospital care.

Medigap plans are organized by letter—labeled A, B, C, D, F, G, K, L, M and N. Each lettered policy is standardized, meaning all policies labeled with the same letter have the same benefits no matter which company provides them. For example, Medigap policy G offered by company 1 provides the exact same benefits as Medigap policy G offered by company 2, even though the premiums may be different.