Coinsurance is the percentage of a covered medical bill that you pay after you have already met your annual deductible. Your insurance company pays the rest. For example, with 20% coinsurance, you pay 20¢ of every dollar — your insurer pays the other 80¢.
How Coinsurance Works, Step by Step
Understanding coinsurance requires knowing where it fits in your plan’s overall cost-sharing structure. Health insurance typically has three layers of cost-sharing before the insurer picks up 100%:
📊 The 3 Phases of Health Insurance Cost Sharing
1
Deductible Phase
You pay 100% of covered costs until your annual deductible is met.
You Pay Everything
2
Coinsurance Phase
Deductible is met. Now you and your insurer split costs based on the coinsurance percentage.
Cost Sharing Begins
3
Out-of-Pocket Max Hit
You’ve spent your annual out-of-pocket maximum. Insurance now covers 100% of covered costs.
Insurer Pays 100%
Phase 1 — Deductible: You pay 100%Phase 2 — Coinsurance: You pay your %Phase 3 — After OOP Max: Insurer pays 100%
Coinsurance only kicks in during Phase 2 — after your deductible is satisfied. This is a key point many people miss. Before you meet your deductible, you pay the full allowed amount for care regardless of your coinsurance rate.
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What Is the “Allowed Amount”?
Coinsurance is calculated on the allowed amount — the rate your insurer has pre-negotiated with the provider. This is usually much lower than the provider’s sticker price. If you use an in-network provider, you benefit from these discounted rates.
The Coinsurance Formula (with Examples)
The math behind coinsurance is straightforward once you know the formula. Here’s how it breaks down:
💡 The Coinsurance Formula
Allowed Amount
×
Your % = Your Cost
+
Insurer % = Insurer Cost
Example — 80/20 Plan, $1,000 Bill (after deductible met)
🔵 Allowed Amount: $1,000
🔴 Your share (20%): $200
🟢 Insurance pays (80%): $800
Three Real-World Worked Examples
Let’s see how coinsurance plays out across different plan types and medical events:
🏥 ER Visit — 80/20 Plan
Total ER Bill$8,000
Allowed Amount$5,500
Deductible Remaining$0 (already met)
Coinsurance80/20
Insurance Pays (80%)$4,400
You Owe (20%)$1,100
💊 Specialist Visit — 70/30 Plan
Specialist Bill$400
Allowed Amount$320
Deductible Remaining$0 (already met)
Coinsurance70/30
Insurance Pays (70%)$224
You Owe (30%)$96
🔬 Lab Work — 90/10 Plan
Lab Bill$750
Allowed Amount$600
Deductible Remaining$0 (already met)
Coinsurance90/10
Insurance Pays (90%)$540
You Owe (10%)$60
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When Part of the Bill Is Still in Your Deductible
If your deductible isn’t fully met, things get slightly more complex. Say your deductible is $1,000 and you’ve paid $800 — you still owe $200 toward it. On a $1,000 allowed bill, you’d pay $200 toward the deductible first, then 20% coinsurance on the remaining $800 = $160. Total: $360 out of pocket.
Common Coinsurance Rates Explained
Health plans use different coinsurance splits. The ratio always reflects: [Insurer pays] / [You pay]. Here are the most common ones and what they mean in practice:
10%
You Pay / 90% Insurer
Lowest cost-sharing. Usually paired with the highest monthly premiums. Best for frequent medical users.
20%
You Pay / 80% Insurer
The most common coinsurance rate. Standard for most employer-sponsored and ACA silver plans.
30%
You Pay / 70% Insurer
Mid-range. Lower premiums but higher per-service costs. Common in bronze-tier or high-deductible plans.
40–50%
You Pay / 60–50% Insurer
High cost-sharing. Often seen in out-of-network situations or very low-premium catastrophic plans.
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ACA Metal Tiers and Coinsurance
ACA Marketplace plans are structured by metal tier, which roughly maps to how costs are shared: Platinum (90/10), Gold (80/20), Silver (70/30), and Bronze (60/40). The actuarial value of each tier reflects what percentage of average costs the insurer covers across all enrollees.
Coinsurance vs. Copay vs. Deductible
These three terms all refer to money you pay out of pocket — but they work very differently. Confusing them is one of the most common mistakes people make when choosing or using a health plan.
Term
What It Is
How It’s Calculated
When You Pay It
Example
Deductible
Annual amount you pay before insurance helps
Fixed Dollar Amount
At the start of each plan year, before most coverage kicks in
$1,500/year deductible — you pay first $1,500 of covered care
Copay
Flat fee for a specific type of visit or service
Fixed Dollar Amount
At the time of service, often before deductible is met
$30 copay every time you see a primary care doctor
Coinsurance
Your percentage share of a medical bill
Percentage of Allowed Cost
After your deductible is met, until you hit your OOP max
20% of a $1,000 allowed bill = $200 you owe
Out-of-Pocket Maximum
Annual cap on your total spending
Fixed Dollar Amount
After this is reached, insurer covers 100% of covered costs
$6,000 OOP max — once hit, you owe $0 for the rest of the year
Copay vs. Coinsurance: Which Costs More?
It depends on the cost of your care. Copays are predictable — you know exactly what you’ll pay before the visit. Coinsurance is variable — the higher the bill, the more you pay. For a $50 doctor visit, a $30 copay is more expensive than 20% coinsurance ($10). For a $2,000 procedure, 20% coinsurance ($400) far exceeds a $50 copay.
Some plans use copays for routine care (primary care, prescriptions) and coinsurance for major care (surgery, hospitalization, specialist procedures). This hybrid approach is very common in employer-sponsored plans.
The Out-of-Pocket Maximum: Your Safety Net
The out-of-pocket maximum (OOP max) is the single most important consumer protection in health insurance. It caps your total annual spending on deductibles, copays, and coinsurance for covered in-network services.
Once you hit your OOP max, your plan pays 100% of covered costs for the rest of the plan year — no coinsurance, no copays.
📊 Example: $6,000 Out-of-Pocket Maximum (Individual)
Deductible — $1,50025% of OOP Max
$1,500 Deductible
Coinsurance (20%) — up to $4,500 more75% of OOP Max
Up to $4,500 in Coinsurance
Total OOP Max$6,000
$6,000 — After This, Insurer Pays 100%
Deductible
Coinsurance Spending
Full OOP Max
For 2025, the ACA-set OOP maximums are $9,200 for individuals and $18,400 for families on marketplace plans. Employer-sponsored plans may have lower caps.
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What Counts Toward Your OOP Max?
Deductibles, copays, and coinsurance for covered in-network services all count. Premiums, out-of-network costs (on most plans), and non-covered services typically do not count toward your OOP maximum.
In-Network vs. Out-of-Network Coinsurance
Most health plans have separate coinsurance rates for in-network and out-of-network providers — and the difference can be dramatic.
In-network coinsurance applies when you see a provider who has a contracted agreement with your insurer. These providers accept the insurer’s negotiated rates, so your coinsurance is applied to a discounted allowed amount.
Out-of-network coinsurance is typically much higher — often 40–50% compared to 20% in-network. Worse, out-of-network providers may bill above the allowed amount, and the difference (called balance billing) is your responsibility on top of the coinsurance. Some HMO plans cover no out-of-network care at all.
Factor
In-Network
Out-of-Network
Typical Coinsurance
10%–30%
30%–50% (or no coverage)
Allowed Amount Basis
Negotiated discounted rate
Often the full billed charge
Balance Billing Risk
None (prohibited in-network)
Possible — you pay the difference
Counts Toward Deductible?
Yes
Often no (plan-dependent)
Counts Toward OOP Max?
Yes
Often no (plan-dependent)
⚠️
Always Verify Network Status Before Care
Even at an in-network hospital, individual physicians (anesthesiologists, radiologists, assistants) can be out-of-network. The No Surprises Act of 2022 provides some protection against unexpected out-of-network bills for emergency and certain scheduled care — but it’s still smart to confirm before procedures.
Tips for Choosing the Right Coinsurance Rate
Selecting a plan based on coinsurance alone is a mistake — it has to be weighed against your premium, deductible, and expected healthcare use. Here’s a practical framework:
Choose Lower Coinsurance (10%–20%) If:
You have a chronic condition, take ongoing medications, expect surgery or hospitalization, have young children who need frequent care, or have had high medical bills in recent years. Lower coinsurance means you pay less per medical event, but you’ll pay more in monthly premiums.
Choose Higher Coinsurance (30%–40%) If:
You are generally healthy, rarely use medical services, want to minimize monthly premium costs, or are comfortable taking on more financial risk for routine care. Pair a high-coinsurance plan with a Health Savings Account (HSA) if eligible — HSA funds can be used tax-free to cover coinsurance and other out-of-pocket costs.
Always Check These Three Numbers Together:
Before choosing a plan, compare the monthly premium × 12 (annual cost of just holding the plan) + deductible + coinsurance liability up to the OOP max. This gives you the maximum you could spend in a year — your worst-case scenario — and helps you make an apples-to-apples comparison between plans.
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Use the Plan’s Summary of Benefits and Coverage (SBC)
Every health plan is legally required to provide an SBC — a standardized two-page document that shows exactly what you pay for common medical scenarios. This makes it easy to compare coinsurance across plans side by side.
⭐ Bottom Line
Coinsurance is the percentage of covered medical costs you share with your insurer after your deductible is met. A 20% coinsurance rate on an 80/20 plan means you pay $200 on a $1,000 allowed bill — your insurer covers the rest. Coinsurance accumulates until you hit your out-of-pocket maximum, after which your insurer pays 100%. Choosing the right coinsurance rate means balancing your monthly premium budget against your expected healthcare needs — and always verifying you’re seeing in-network providers to keep your costs as low as possible.
Frequently Asked Questions
Coinsurance is the percentage of a covered medical bill that you pay after you have met your annual deductible. For example, with 20% coinsurance, you pay 20% of the allowed amount for a service and your insurer pays the remaining 80%. Unlike a copay (which is a flat fee), coinsurance scales with the cost of care.
A copay is a fixed dollar amount you pay for a specific service — for example, $30 for every primary care visit, regardless of what that visit actually costs. Coinsurance is a percentage of the total allowed cost, so it varies depending on how expensive the service is. Copays are predictable; coinsurance is not. Many plans use copays for routine visits and coinsurance for major services like surgery or hospitalization.
Coinsurance applies after you have met your deductible for the year. During the deductible phase, you pay 100% of covered medical costs. Once your deductible is satisfied, coinsurance kicks in and you share costs with your insurer at the plan’s stated ratio — for example, you pay 20% and the insurer pays 80%.
80/20 coinsurance means your insurance company pays 80% of the covered allowed amount for a service after your deductible is met, and you pay the remaining 20%. On a $1,000 allowed bill, you would owe $200 and your insurer would pay $800. This is the most common coinsurance ratio in the U.S. and is standard on ACA Gold-tier plans.
Yes — your out-of-pocket maximum acts as a hard cap. Once your total spending (deductibles + copays + coinsurance) for covered in-network services reaches the OOP max, your insurer pays 100% of covered costs for the rest of the plan year. For 2025, the ACA-set OOP max limits are $9,200 for individuals and $18,400 for families on marketplace plans.
It depends on your health needs and budget. A 10% or 20% coinsurance is generally considered favorable — you pay less per medical event — but these plans usually carry higher monthly premiums. A 30–40% coinsurance means lower premiums but higher costs when you actually use care. If you’re in good health and rarely see doctors, a higher coinsurance with lower premiums can save money overall. If you have ongoing medical needs, a lower coinsurance plan usually wins out.
It depends on your plan. Some plans use coinsurance for prescription drugs (especially for brand-name or specialty drugs), while others use fixed copays by tier. Your plan’s formulary (drug list) will specify whether coinsurance or copays apply to different drug categories. Specialty drugs often have the highest coinsurance — sometimes 20–33% of the drug’s cost, which can be thousands of dollars per month for expensive biologics.
Under the ACA, certain preventive services — like annual wellness visits, mammograms, colonoscopies, and recommended vaccines — must be covered with no cost sharing at all when received in-network. This means $0 coinsurance and $0 copay for those specific services, regardless of whether your deductible is met. Beyond that, coinsurance is a standard plan feature and is generally not negotiable, though you can appeal specific claims if you believe a billing error occurred.
📌 This article is for informational purposes only. Health plan structures vary. Always review your plan’s Summary of Benefits and Coverage (SBC) or contact your insurer directly to confirm your specific coinsurance rates and how they apply to your care.
