A health insurance policy that helps pay for some of the costs that Original Medicare doesn't cover.
Medicare Supplement Insurance (Medigap) is extra insurance you can buy from a private health insurance company to help pay your share of out-of-pocket costs in.
Who can buy it
You usually need to have Medicare Part A and Part B to buy a Medigap policy. People under 65 might not be able to buy a Medigap policy, or they may have to pay more.
What it covers
Medigap helps pay for out-of-pocket costs like copayments, coinsurance, and deductibles. Some Medigap policies also cover services that Original Medicare doesn't, like emergency medical care when you travel outside the U.S..
What it doesn't cover
Medigap policies generally don't cover long-term care, vision, dental, hearing aids, private-duty nursing, or prescription drugs.
Renewability
As long as you pay your premium, your Medigap policy is guaranteed renewable, which means it is automatically renewed each year.