Original Medicare pays for many, but not all, health care services and supplies. A Medicare Supplement Insurance policy (or “Medigap” policy), sold by private companies, helps pay some of the health care costs (or “gaps”) that Original Medicare doesn’t cover – like copayments, coinsurance, and deductibles.
Some Medigap policies also offer coverage for 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, Medicare will pay its share of the Medicare-approved amount for covered health care costs. Then, your Medigap policy pays its share.
A Medigap policy is different from a Medicare Advantage Plan (like an HMO or PPO) because those plans are ways to get your Medicare benefits, while a Medigap policy only supplements your Original Medicare benefits. It’s illegal for an insurance company to sell a Medigap policy to anyone who is still enrolled in a Medicare Advantage Plan. If you have a Medicare Advantage Plan and want to return to Original Medicare, you can buy a Medigap policy that will start when your coverage begins under Original Medicare.