Coinsurance is your share of the costs for covered health care services. It is calculated as a percentage (for example, 20%) of the allowable amount for the service. You pay the coinsurance amount plus your plan deductible (if not already satisfied).
As an example, if your health insurance allowed amount for an office visit is $100, and you’ve met your deductible, your coinsurance payment of 20% would be $20. If you had not met your deductible, you would need to pay the full amount for service provided: $100.