Medicare Supplement insurance (Medigap)
is private insurance that pays for health expenses that Original Medicare does not cover (copayments, coinsurance, deductibles). Medigap policies are sold by private companies.
When you have Original Medicare and you purchase a Medigap policy, Medicare will pay for 80% of Medicare-approved health expenses. Then, your Medigap policy will supplement the 20% gap in coverage by paying its share.
You pay the private insurance company a monthly premium for your Medigap policy. You pay this premium in addition to the monthly Part B premium that you pay to Medicare. You can buy a Medigap policy from any insurance company that’s licensed in your state to sell one.