Coinsurance
The percentage of covered medical expenses you share with your insurer after reaching your deductible.
Actuarial & Contractual Mechanics
After meeting your deductible, coinsurance splits covered expenses as a fixed percentage between you and your insurer (typically 80% paid by insurer, 20% by you) until you reach your out-of-pocket maximum. See how coinsurance alters real hospital invoices with our Out-of-Pocket Cost Calculator and review network rules in HMO vs. PPO.
After meeting her $2,000 deductible, Maria needs an outpatient knee surgery costing $5,000. Under an 80/20 plan, her insurer pays 80% ($4,000) and Maria pays 20% ($1,000).
On large hospital bills, a 20% coinsurance share can easily exceed $15,000 without an annual stop-loss cap. Review policy mechanics in our Health Insurance Basics Guide and check Does Health Insurance Cover Out-of-Network ER Visits?.
Frequently Asked Questions About Coinsurance
Clear definitions, policy implications, and related coverage calculators.