Coinsurance
The percentage of costs you share with your insurer after meeting your deductible — for example, you pay 20%, your insurer pays 80%.
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.
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 — 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.
What's better — 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.
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