While Original Medicare covers many health services, it doesn’t cover everything. You’ll still have to pay deductibles, co-payments, and coinsurance.
Medicare Supplement (also called Medigap) plans help fill the “gaps” in coverage by paying for some of the costs that Original Medicare doesn’t cover.
To enroll in a Medigap plan, you must be enrolled in Original Medicare, Part A and Part B, and live in the service area of the Medigap plan you want to join.
Medicare Supplement plans only work with Original Medicare. If you are enrolled in a Medicare Advantage plan, a Medigap plan can’t be used to pay for Medicare Advantage costs.