Coinsurance is the percentage of a medical bill you pay after you’ve met your deductible. If your plan has 20% coinsurance, you pay 20% of every covered medical expense and your insurance company pays the remaining 80%. This cost-sharing continues until you hit your plan’s out-of-pocket maximum, at which point your insurer covers 100% of eligible costs for the rest of the plan year.
How the Payment Sequence Works
Health insurance costs follow a predictable order. First, you pay your monthly premium just to keep your coverage active. Then, when you receive medical care, you pay the full allowed cost out of pocket until you’ve spent enough to meet your annual deductible. Once that deductible is satisfied, coinsurance kicks in and you start splitting costs with your insurer. Finally, once your total out-of-pocket spending (deductible plus coinsurance combined) reaches your plan’s annual cap, your insurance pays 100% of covered services for the remainder of the year.
Think of the deductible as the entrance fee. Coinsurance is what you pay once you’re through the door, and the out-of-pocket maximum is the ceiling that protects you from runaway costs.
Common Coinsurance Splits
The most common coinsurance arrangement is an 80/20 split, meaning your insurer pays 80% and you pay 20%. Other plans use 70/30 or 60/40 splits, where you take on a larger share of costs in exchange for lower monthly premiums. Some plans offer 90/10 coinsurance, which means smaller bills after the deductible but higher premiums up front.
The percentage listed on your plan documents is almost always your share, not the insurer’s. So “20% coinsurance” means you owe 20%.
A Real Cost Breakdown
Here’s how coinsurance plays out on an actual bill. Say you need treatment for a serious condition and the total allowable costs come to $12,000. Your plan has a $3,000 deductible, 20% coinsurance, and a $6,850 out-of-pocket maximum.
- Deductible phase: You pay the first $3,000 entirely out of pocket.
- Coinsurance phase: The remaining $9,000 is subject to your 20% coinsurance. Your share is $1,800. Your insurer pays $7,200.
- Total out-of-pocket cost: $3,000 + $1,800 = $4,800.
For a smaller expense like a $100 office visit after you’ve already met your deductible, you’d simply pay $20 (20% of $100) and your insurer would cover the other $80.
When Coinsurance Stops
Coinsurance doesn’t continue indefinitely. Every plan has an out-of-pocket maximum, and once your combined deductible payments and coinsurance reach that number, your plan covers 100% of covered costs for the rest of the plan year. For high-deductible health plans in 2026, federal rules cap out-of-pocket expenses at $8,500 for individual coverage and $17,000 for family coverage. Many employer plans set their limits below these federal caps.
This ceiling is what makes coinsurance manageable even when you’re facing major surgery or ongoing treatment. The 20% you owe on a $50,000 hospital stay would be $10,000 in theory, but your out-of-pocket maximum stops your actual cost well short of that.
In-Network vs. Out-of-Network Coinsurance
Your coinsurance percentage typically changes depending on whether you see an in-network or out-of-network provider. A plan might charge 20% coinsurance for in-network care but 40% for out-of-network care. On top of the higher percentage, out-of-network providers can bill above the amount your insurance considers “allowed,” and that difference often doesn’t count toward your out-of-pocket maximum. This is one of the fastest ways to end up with an unexpectedly large medical bill.
Services That Skip Coinsurance Entirely
Under the Affordable Care Act, most health plans must cover a set of preventive services at no cost to you. This includes immunizations, cancer screenings, blood pressure checks, and other routine preventive care. You won’t pay coinsurance or even a copay for these services when you use an in-network provider, even if you haven’t met your deductible yet. This is a notable exception to the usual payment sequence.
Coinsurance vs. Copays
Coinsurance and copays both represent your share of a medical bill, but they work differently. A copay is a flat dollar amount, like $30 for a doctor’s visit, regardless of the total cost. Coinsurance is a percentage, so your actual cost scales with the size of the bill. Many plans use both: copays for routine visits and prescriptions, coinsurance for bigger-ticket items like hospital stays, imaging, and specialist procedures.
When comparing plans, pay attention to how these interact. A plan with low coinsurance but a high deductible means you’ll pay less per visit once you clear the deductible, but it takes more spending to get there. A plan with a low deductible but higher coinsurance starts sharing costs sooner, but your share of each bill is bigger. The right balance depends on how much care you expect to use in a given year.