Coinsurance

The percentage of covered medical costs you pay after meeting your deductible, with your insurance plan covering the remainder.

Coinsurance is the cost-sharing arrangement that kicks in after you've met your deductible. Once you've paid your deductible for the year, covered medical expenses are split between you and your insurer at a set percentage — commonly 80/20, meaning your insurance pays 80% and you pay 20%. If you receive a $2,000 medical bill after meeting your deductible on an 80/20 plan, you owe $400 and your insurance covers $1,600. This sharing continues until you hit your annual out-of-pocket maximum, at which point your insurance covers 100% of additional covered costs for the rest of the plan year.

Coinsurance is distinct from a copay, though both are forms of cost-sharing. A copay is a fixed dollar amount ($30 for a primary care visit) regardless of the actual service cost. Coinsurance is a percentage of the actual cost — so the amount you pay varies with the cost of the service. Some plans use copays for common services like office visits and prescriptions, and coinsurance for larger expenses like hospitalizations and imaging. Others use coinsurance throughout. Understanding which structure your plan uses matters when estimating out-of-pocket costs for a planned procedure.

Coinsurance percentages vary by plan tier and provider network. In-network coinsurance on a mid-tier employer plan is commonly 20–30%; out-of-network coinsurance is often 40–50% or higher, and some plans offer no out-of-network coverage at all except in emergencies. The combination of your deductible, coinsurance rate, and out-of-pocket maximum defines the complete range of your financial exposure for a given plan year — from minimum (just routine copays in a healthy year) to maximum (hitting the out-of-pocket ceiling after a major illness or surgery).

When comparing health plans during open enrollment, the coinsurance rate is one of three numbers to evaluate together with the deductible and out-of-pocket maximum. A plan with a low deductible but high coinsurance can result in higher total costs than a plan with a moderate deductible and low coinsurance, depending on your utilization level. Modeling a few scenarios — a healthy year, a moderate-utilization year, and a high-utilization year that hits the out-of-pocket max — helps reveal which plan is actually cheaper across a realistic range of outcomes.

Coinsurance vs. Copay: Key Differences

  • Copay: fixed dollar amount per visit or service, predictable, often doesn't require meeting deductible first — e.g., $30 every primary care visit.
  • Coinsurance: percentage of actual cost, variable, applies after deductible is met — e.g., 20% of a $5,000 hospital bill = $1,000 your cost.
  • Some plans use copays for some services and coinsurance for others — e.g., copays for office visits and Rx, coinsurance for hospitalization and surgery.
  • Both copays and coinsurance count toward your out-of-pocket maximum, though plans vary on whether copays count — read your plan documents carefully.

How to Calculate Your Exposure

Your worst-case annual medical cost is your out-of-pocket maximum. To estimate a realistic mid-range scenario: add your expected annual premium cost to your estimated cost-sharing for anticipated services. If you expect two specialist visits at 20% coinsurance after a $1,500 deductible, and each specialist charges $400 (billed), you'd pay the first $1,500 in deductible, then 20% of remaining costs. Model your total insurance cost (premium + expected out-of-pocket) and compare across the plan options available to you — not just the premium headline.

In-Network vs. Out-of-Network Coinsurance

Health plans set different coinsurance rates for in-network and out-of-network providers. In-network providers have negotiated rates with your insurer, so the 'allowed amount' is pre-set and your coinsurance applies to that negotiated rate. Out-of-network providers bill at their own rates, and your insurer may apply coinsurance to a 'usual and customary' amount that's lower than the actual bill — leaving you responsible for both the coinsurance percentage and the difference between the billed amount and what the insurer considers reasonable. Out-of-network coinsurance exposure can be significantly higher than in-network, and some plans (HMOs, EPOs) cover out-of-network care only in emergencies.

Example

After meeting her $1,500 deductible, an employee has an MRI that costs $2,000. Her plan has 20% coinsurance. She pays $400 (20% × $2,000); her insurance pays $1,600. If she later has surgery costing $8,000 (after deductible), she owes $1,600 in coinsurance — bringing her year-to-date cost-sharing to $2,000 plus the deductible. Her out-of-pocket maximum is $4,000, so any further covered costs that year are 100% covered by insurance.