Medicare glossary
Coinsurance
Coinsurance is your share of a cost expressed as a percentage, paid after you've met your deductible. Under Original Medicare Part B, you typically pay 20% coinsurance for many covered services.
Because Original Medicare's 20% coinsurance has no annual limit on its own, costs can add up for major care. That's a key reason people add a Medicare Supplement (which covers much of the coinsurance) or choose a Medicare Advantage plan (which replaces coinsurance with set copays and caps yearly costs).
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