Medicare supplement insurance policies, or Medigap policies, help to pay the copayments, coinsurance, and deductibles for Medicare-covered benefits under traditional Medicare (Part A and Part B services). Some Medigap policies also cover services that traditional Medicare does not cover, such as medical care when you travel outside the country. Medigap policies do not work with Medicare Advantage plans and will not help to cover Medicare Advantage enrollees’ out-of-pocket costs.