A Medicare Supplement Insurance (Medigap) policy helps pay some of the health care costs that Original Medicare doesn't cover, like:

  • Copayments
  • Coinsurance
  • Deductibles

Medigap policies are sold by private companies.

Some Medigap policies also cover services that Original Medicare doesn't cover, like medical care when you travel outside the U.S. If you have Original Medicare and you buy a Medigap policy, here's what happens:

  • Medicare will pay its share of the Medicare-approved amount for covered health care costs.
  • Then, your Medigap policy pays its share.

Source: https://www.medicare.gov/supplements-other-insurance/whats-medicare-supplement-insurance-medigap