What Is Co Insurance? How It Works

The Percentage You Pay After Your Deductible

After you meet your deductible, you might expect your insurance to cover everything. Instead, most plans split the remaining cost between you and your insurer using a percentage-based system. If you have ever wondered what is co insurance, it is exactly this cost-sharing arrangement – the share of each covered medical bill you are responsible for after your deductible has been satisfied.

What is co insurance in practical terms? It is typically expressed as a ratio, such as 80/20: the insurer pays 80 percent and you pay 20 percent of covered services until you reach your out-of-pocket maximum. According to HealthCare.gov, coinsurance is one of the primary ways health insurance plans share costs with members. Understanding how it works helps you predict your medical expenses and choose the right plan, so let’s break it down with real numbers and real scenarios.

How Coinsurance Works Step by Step

Coinsurance kicks in after you have paid your deductible for the year. Before that point, you typically pay the full allowed amount for covered services. Once the deductible is met, you and your insurer begin splitting costs according to your coinsurance rate.

Here is a worked example. You have a plan with a $2,000 deductible and 20 percent coinsurance, and you need a procedure that costs $10,000. Assuming you have not met any of your deductible yet, you pay the first $2,000. The remaining $8,000 is subject to coinsurance: you pay 20 percent of $8,000, which is $1,600, and your insurer pays the other $6,400. Your total responsibility for that procedure is $3,600 ($2,000 deductible plus $1,600 coinsurance).

This cost-sharing continues for every covered service until your total out-of-pocket spending for the year reaches your plan’s maximum. After that point, the insurer covers 100 percent of covered in-network care for the rest of the plan year. Your exact numbers depend on your plan, so always check your plan documents for your specific deductible, coinsurance rate, and out-of-pocket maximum.

Common Coinsurance Ratios and What They Mean

Health plans use different coinsurance splits depending on the plan tier, and understanding these ratios helps you compare options during open enrollment. An 80/20 plan is one of the most common arrangements – the insurer pays 80 percent and you pay 20 percent. A 70/30 plan shifts more cost to you, while a 90/10 plan reduces your share. Bronze plans on the ACA Marketplace typically carry higher coinsurance rates, such as 40 percent, while Gold and Platinum plans generally offer lower rates around 20 percent or less.

The trade-off is straightforward. Plans with lower coinsurance rates usually have higher monthly premiums, while plans with higher coinsurance rates come with lower premiums but expose you to greater costs when you actually use medical services. The Kaiser Family Foundation has reported average coinsurance rates for in-network specialist visits in employer plans in the high-teens percentage range in recent surveys, which gives a sense of what is typical – though your plan may differ.

Coinsurance vs. Copay

These two terms describe different types of cost-sharing, and they work differently at the point of care. A copay is a fixed dollar amount you pay for a specific service, such as $30 for a doctor visit or $15 for a generic prescription. Coinsurance, by contrast, is a percentage of the total allowed cost.

With a $40 copay, you know exactly what you will owe before you walk into the office. With 20 percent coinsurance, your cost depends on the total bill: a specialist visit billed at $300 costs you $60 at 20 percent coinsurance, while the same visit with a $40 copay costs you $40 regardless of the billed amount. The practical difference is predictability versus proportionality.

Many plans use both. You might pay copays for routine office visits and prescriptions while paying coinsurance for hospitalizations, surgeries, and other major services. For a deeper comparison, see our guide on copay vs coinsurance.

How Coinsurance Applies to Different Services

Your coinsurance rate can vary depending on the type of service and whether you stay in-network.

In-Network vs. Out-of-Network

Most plans have different coinsurance rates for in-network and out-of-network providers. You might pay 20 percent coinsurance in-network but 40 percent out-of-network. Beyond the higher percentage, out-of-network providers can also charge more than your plan’s allowed amount, potentially leaving you responsible for the difference through balance billing – though federal surprise-billing protections limit this in certain emergency and facility situations. Confirm network status before you receive care.

Hospital and Surgical Services

Inpatient hospital stays and surgeries are where coinsurance has the biggest financial impact. A $50,000 surgery at 20 percent coinsurance would be $10,000 out of pocket on paper, but your out-of-pocket maximum caps the total you can be charged for covered in-network care. This is exactly why understanding your maximum alongside your coinsurance rate is so important.

Prescription Drugs

Some plans apply coinsurance rather than flat copays to prescription drugs, particularly specialty and biologic medications. A drug costing $5,000 per month at 30 percent coinsurance would run $1,500 per fill before any assistance. Many plans cap specialty drug cost-sharing or point members to manufacturer or foundation assistance programs, so check your plan’s formulary and pharmacy benefit.

Coinsurance and Your Out-of-Pocket Maximum

Coinsurance payments count toward your annual out-of-pocket maximum. Once your deductible, copays, and coinsurance add up to that limit, your plan pays 100 percent of covered in-network services for the rest of the year. Premiums and out-of-network charges generally do not count toward the maximum.

Federal rules cap how high that maximum can go. For 2026, the ACA limits in-network out-of-pocket spending to no more than about $10,600 for an individual and $21,200 for a family (these figures are updated annually, so verify the current limits for your plan year). Many employer and Marketplace plans set their maximums below these federal ceilings.

Using the earlier example with a $2,000 deductible, 20 percent coinsurance, and, say, a $7,000 out-of-pocket maximum: after paying the $2,000 deductible you have $5,000 of exposure left before hitting your cap. At 20 percent coinsurance, you would need roughly $25,000 in additional covered charges before your coinsurance alone reaches that remaining $5,000 – after which full coverage kicks in for the rest of the year.

How to Minimize Your Coinsurance Costs

Several strategies can help you reduce what you pay through coinsurance. First, stay in-network – the difference between in-network and out-of-network coinsurance can double or triple your share, so verify that your provider, facility, and any specialists involved in your care are in-network before receiving services.

Second, use a health savings account or flexible spending account to pay coinsurance with pre-tax dollars. This effectively discounts your costs by your marginal tax rate; if you are in the 22 percent bracket, paying coinsurance from an HSA saves you about 22 cents on every dollar. Third, compare plans during open enrollment with your expected medical usage in mind – if you anticipate high costs, a plan with lower coinsurance and a higher premium may save money overall. Run the numbers using your anticipated procedures and prescriptions rather than premiums alone.

Frequently Asked Questions

Do I pay coinsurance before or after my deductible?

After. Coinsurance applies to covered services once you have met your annual deductible. Before the deductible is met, you generally pay the full allowed amount for most services. Some plans cover certain services with a copay before the deductible, but coinsurance for the bulk of care begins after the deductible is satisfied.

Does coinsurance apply to preventive care?

Under the ACA, most in-network preventive services are covered at 100 percent with no cost-sharing – no coinsurance, copay, or deductible. This includes many annual wellness exams, recommended vaccinations, and specific screenings. Once a visit shifts from preventive to diagnostic, coinsurance may apply.

Can my coinsurance rate change during the year?

Your coinsurance rate is fixed for the plan year and cannot change until your plan renews, typically on January 1 for calendar-year plans. If you switch plans mid-year through a qualifying life event, the new plan’s coinsurance rate applies going forward.

Is 20 percent coinsurance good?

A 20 percent coinsurance rate is among the most common and is generally considered favorable, meaning your insurer covers 80 percent of costs after your deductible. Lower rates like 10 percent are better for you at the point of care but usually come with higher premiums, while higher rates like 30 or 40 percent lower premiums but increase your risk of large bills.

Making Coinsurance Work in Your Favor

Coinsurance is one of those insurance terms that seems abstract until you face a significant medical bill. Knowing your coinsurance rate, understanding when it applies, and pairing it with a clear picture of your deductible and out-of-pocket maximum gives you the tools to plan and budget for healthcare costs. Compare plans based on total potential costs rather than premiums alone, confirm network status before receiving care, and read your own plan documents so there are no surprises. For a comprehensive look at how all of these costs interact, visit our healthcare costs guide.

Sources

• HealthCare.gov – glossary entries for Coinsurance, Deductible, and Out-of-pocket maximum/limit, including 2026 out-of-pocket limits (healthcare.gov)
• Centers for Medicare & Medicaid Services (CMS) – Marketplace cost-sharing and annual limitation on cost-sharing standards (cms.gov)
• Kaiser Family Foundation (KFF) – Employer Health Benefits Survey, cost-sharing averages (kff.org)