100 coinsurance in health insurance means you pay 100% of covered costs after meeting your deductible until reaching your out-of-pocket maximum. This is the highest coinsurance percentage possible.
| Percentage | Your Responsibility | Insurer's Responsibility |
|---|---|---|
| 100% | All costs after deductible | None until out-of-pocket max |
| 80/20 | 20% of costs | 80% of costs |
| 70/30 | 30% of costs | 70% of costs |
This structure is rare but may appear in certain plans or for specific services. For example, some high-deductible plans might use 100 coinsurance for non-network services, forcing members to pay the full billed amount. Other plans might apply it to experimental treatments not fully covered by the insurer.
I once reviewed a plan that had 100 coinsurance for out-of-network emergency care. This meant if you were treated at an out-of-network hospital in an emergency, you'd pay the entire bill after your deductible, even if the insurer later negotiated a lower rate with the provider.
Many people confuse coinsurance with premium conversion or assume all plans have the same coinsurance structure. In reality, coinsurance percentages vary widely between plans and services. Some plans might have different coinsurance levels for different types of care, such as 20% for hospital stays but 100% for certain medications.
Another mistake is thinking coinsurance applies to all medical expenses. Typically, it only kicks in after you've met your deductible. Before that point, you're usually paying 100% of costs anyway.
Consider a plan with a $2,000 deductible and 100 coinsurance for non-network services. If you're treated at an out-of-network facility for $10,000:
This is much higher than if you had a more typical coinsurance structure.
Insurers might implement 100 coinsurance to discourage certain behaviors, like using out-of-network providers or seeking expensive treatments. It also shifts more financial risk to the insured, which can help keep premiums lower for everyone in the plan.
According to the Kaiser Family Foundation, about 29% of employer-sponsored plans have coinsurance structures, though most are more balanced than 100%. The use of high coinsurance percentages has been increasing in recent years as insurers look for ways to control costs.