Glossary
Medigap (Medicare Supplement Insurance)
Extra insurance bought from a private company to help pay your share of costs in Original Medicare.
Medigap, also called Medicare Supplement Insurance, is extra insurance sold by private companies to help cover your share of costs in Original Medicare, such as coinsurance, copayments, and deductibles. It works alongside Original Medicare rather than replacing it, and it does not include drug coverage, so Part D is bought separately. Medigap is sold in standardized types named by letters, and the same letter covers the same things whichever company sells it. Where companies differ is price and service. Medigap spreads costs differently over a year than Medicare Advantage does: you pay a steady monthly premium in exchange for smaller and more predictable bills when care happens, and you keep the freedom to use any provider who accepts Medicare. This matters to you because of timing. There is a one-time Medigap open enrollment period, six months long, that begins when you are 65 or older and enrolled in Part B, during which your health history cannot be used to refuse you or raise your price. Outside that window, in most states, it can. Your State Health Insurance Assistance Program counselor can walk through what is sold in your state, free of charge.