Medicare Supplement Insurance, also known as Medigap plans, help fill "gaps" in Original Medicare and are sold by private insurance companies. Original Medicare pays for much, but not all, of the cost for covered health care services and supplies. A Medicare Supplement Insurance (Medigap) policy can help pay some of the remaining health care costs, like co-payments, co-insurances and deductibles.

A Medigap policy is different from a Medicare Advantage Plan. Those plans are ways to get Medicare benefits, while a Medigap policy only supplements your Original Medicare benefits. You pay a private insurance company a monthly premium for your Medigap policy. You pay this monthly premium in addition to the monthly Part B premium that you pay to Medicare.

Medigap policies generally don't cover long-term care, vision or dental care, hearing aids, eyeglasses, or private-duty nursing.