Co-insurance is your share of the costs of a covered health care service, calculated as a percent (for example, 20%) of the eligible charge for the service. You pay co-insurance plus any deductibles you owe. For example, if your health plan’s eligible charge for an office visit is $100 and you’ve met your deductible, your co-insurance payment of 20% would be $20. The health insurance or plan pays the rest of the eligible charge.

A co-payment is a fixed amount (for example, $15) you pay for a covered health care service. The amount can vary by the type of covered health care service.