What Is Coinsurance? And How It Affects Your Bills

You met your deductible. Great. Now insurance pays for everything, right? Not quite. Most plans still require you to pay a percentage of each bill. That percentage is your coinsurance, and it can add up fast if you need expensive care.

How Coinsurance Works

Coinsurance kicks in after you've met your deductible. If your plan has 20% coinsurance, you pay 20% of covered services and the insurer pays 80%. This is the most common split, though it varies by plan and service type.

Here's a real example. You've already met your $1,500 deductible. You need a procedure that costs $10,000 at the negotiated rate. With 20% coinsurance, you pay $2,000 and the insurer covers $8,000. That $2,000 counts toward your out-of-pocket maximum.

Coinsurance by Plan Tier

ACA Marketplace plans use metal tiers that roughly correspond to how costs are split. Bronze plans cover about 60% of costs (you pay 40%). Silver plans cover 70%. Gold covers 80%. Platinum covers 90%. These are averages across all your care for the year, not exact coinsurance rates for every service, but they give you a useful ballpark.

In-Network vs. Out-of-Network Coinsurance

Most plans charge different coinsurance rates depending on whether you use an in-network or out-of-network provider. A plan might charge 20% coinsurance in-network but 40% or even 50% for out-of-network care. Worse, out-of-network costs sometimes don't count toward your out-of-pocket maximum at all. That means there's no ceiling on what you could owe for out-of-network services.

The No Surprises Act, effective since January 2022, does protect you in specific situations. If you go to an in-network hospital but get treated by an out-of-network doctor you didn't choose (an anesthesiologist, for example), the law limits what you can be charged to in-network rates.

When Coinsurance Stops

Coinsurance payments stop once you reach your out-of-pocket maximum. For 2026, ACA plans cap this at $10,150 for individuals and $20,300 for families. After that, the plan covers 100% of in-network covered services for the rest of the plan year. This is why the out-of-pocket max matters more than the coinsurance rate if you're expecting a major surgery or expensive treatment.

Coinsurance vs. Copay

People mix these up constantly. A copay is a fixed dollar amount ($26 for a doctor visit, for instance). Coinsurance is a percentage. With a copay, you know exactly what you'll owe before you walk in. With coinsurance, your cost depends on the total bill. Twenty percent of a $500 lab bill is $100. Twenty percent of a $50,000 hospital stay is $10,000.

Many plans use both. You might pay a $26 copay for a routine office visit but 20% coinsurance for surgery. Both copays and coinsurance count toward your annual out-of-pocket maximum.