Coinsurance
Updated for plan year 2026
In plain terms
Coinsurance is the share of a covered service's cost you pay as a percentage, after you've met your deductible. If your coinsurance is 20 percent, the plan pays 80 percent of the allowed amount and you pay the rest. Unlike a flat copay, coinsurance scales with the price of the care, so a major procedure costs you more than a minor one. You keep paying your percentage until your spending reaches the out-of-pocket maximum, after which the plan covers 100 percent of covered care.
A plain example
Your plan pays 80 percent and you pay 20 percent coinsurance after the deductible. You've already met your deductible, then have an outpatient procedure with a $5,000 allowed cost. Your share is 20 percent, or $1,000, and the plan pays the other $4,000. If you'd had a $500 service instead, your 20 percent would be just $100.
Why it matters
Coinsurance is why an unmet deductible isn't the end of your costs. On a big hospital bill, 20 percent of the allowed amount can still run into thousands. It's also the main difference between metal tiers: a gold plan's lower coinsurance trades a higher premium for smaller bills when you need care.
A common point of confusion
Coinsurance and copays are not the same. A copay is a fixed dollar amount set in advance; coinsurance is a percentage that rises with the cost of the service, so you don't know the exact figure until the bill arrives.