Definition. The part of a covered service's cost you pay after any deductible, usually stated as a percentage (Part B) or a set daily amount (Part A hospital and skilled nursing stays).
What it means
Coinsurance is different from a copayment, which is a flat dollar amount. Under Original Medicare in 2026:
- Part B: usually 20% of the Medicare-approved amount for doctor visits, outpatient care and medical equipment, after the $283 deductible. Many preventive services cost $0 when the provider accepts assignment.
- Part A hospital: $434 a day for days 61 to 90 of a benefit period, and $868 a day for lifetime reserve days.
- Skilled nursing facility: $217 a day for days 21 to 100.
Original Medicare has no out-of-pocket maximum. Medigap policies pay all or part of this coinsurance, depending on the plan letter. Medicare Advantage plans set their own copays and coinsurance and must cap in-network costs (at most $9,250 in 2026).
Sources
- CMS — 2026 Medicare Parts A & B premiums and deductibles
- Medicare.gov — Medicare costs
- Medicare.gov — Choosing a Medigap policy (PDF)
Frequently asked questions
What's the difference between coinsurance and a copay?
Coinsurance is a percentage of the cost, such as 20% of the Medicare-approved amount. A copay is a set dollar amount per service. Original Medicare mostly uses coinsurance; Medicare Advantage and Part D plans often use copays.
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