A Medicare Supplement (also known as Medigap) policy is an insurance policy that helps supplement Original Medicare and is sold by private companies. A Medicare Supplement policy can help pay some of the remaining health care costs that Original Medicare doesn't pay for covered services and supplies, like co-insurance, co-payments and deductibles. Original Medicare pays for much but not all, of the cost for covered health care services and supplies.

​

Every Medicare Supplement policy must follow federal and state laws designed to protect you, and they must clearly identify as "Medicare Supplement Insurance." Insurance companies can sell you only a "standardized" policy identified in most states by letters A through D, F, G, and K through N. All policies offer the same basic benefits, but some offer additional benefits so you can choose which one meets your needs. In Massachusetts, Minnesota, and Wisconsin, Medicare Supplement policies are standardized in a different way.