Coinsurance
The percentage of costs you share with your insurer after meeting your deductible, for example, you pay 20%, your insurer pays 80%.
Last reviewed August 23, 2026
Definition
Coinsurance is the percentage of covered healthcare costs that you pay after meeting your deductible, with your insurer paying the remaining percentage. Common splits are 80/20 (insurer pays 80%, you pay 20%) or 70/30.
Unlike a copay (a fixed dollar amount), coinsurance is a percentage, so your share scales with the cost of the service. A 20% coinsurance on a $10,000 surgery means you owe $2,000; on a $500 procedure, you owe $100.
The sequence for a typical health insurance claim:
1. You pay 100% until you meet your deductible
2. After the deductible, you pay your coinsurance percentage (e.g., 20%) and the insurer pays the rest (80%)
3. Once you reach your out-of-pocket maximum, the insurer pays 100%
Coinsurance is one of the most important cost drivers for major medical events. A 20% coinsurance on a $50,000 hospitalization is $10,000, which is why the out-of-pocket maximum exists as a backstop.
Coinsurance is one of the lines on an Explanation of Benefits that is most often misread as a bill. How to read an EOB covers the difference.
Examples
After meeting your $1,500 deductible, you have a $5,000 procedure. With 20% coinsurance, you pay $1,000 (20% of $5,000); your insurer pays $4,000.
Your plan is 70/30. You've met your deductible. A $300 specialist visit costs you $90 (30% of $300).
You've met both your deductible and your $6,000 out-of-pocket max. All remaining covered services this year are 100% covered by insurance, and coinsurance no longer applies.
Frequently asked questions
When does coinsurance apply?
Coinsurance applies after you've met your deductible. Before meeting the deductible, you pay 100% of covered costs. After meeting the out-of-pocket max, you pay 0%.
Is coinsurance the same for all services?
No. Plans can have different coinsurance rates for different services, for example, 20% for primary care but 30% for out-of-network specialists. Always check your plan's Summary of Benefits.
Which is better, a copay or coinsurance?
Copays are predictable (fixed dollar amounts). Coinsurance is unpredictable but may be cheaper for low-cost services. For expensive care (surgeries, hospitalizations), coinsurance can be significantly higher than a flat copay. Plans with copays for common services and coinsurance for major care offer a balance of predictability and protection.
Related terms
Deductible
The amount you pay out of pocket for covered services before your insurance begins to pay.
Premium
The recurring payment you make, monthly, quarterly, or annually, to maintain an insurance policy.
Out-of-pocket maximum
The most you'll ever pay in a plan year for covered services, after which your insurance pays 100%.
Copay
A fixed dollar amount you pay for a specific healthcare service, like $25 for a doctor visit, regardless of the total bill.
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