Coinsurance in Health Insurance: What It Is and How It Really Works

Understanding health insurance often comes down to decoding a few key terms—and coinsurance is one of the most important. Knowing what coinsurance is, how it’s calculated, and when it applies can make a big difference in what you actually pay for care.

This guide breaks coinsurance down in clear, practical language so you can read your health plan with confidence and avoid surprise medical bills.

What Is Coinsurance in Health Insurance?

Coinsurance is the percentage of covered medical costs you pay after you’ve met your deductible. The health insurance company pays the remaining percentage.

• If your coinsurance is 20%, you pay 20% of the allowed cost.
• Your health plan pays the other 80%—until you reach your out-of-pocket maximum.

Coinsurance typically applies to many services after:

1. You’ve paid your deductible, and
2. The service is covered and medically necessary under your plan.

Coinsurance vs. Copay vs. Deductible vs. Out-of-Pocket Maximum

These terms are easy to mix up. Here’s how they fit together.

Key Definitions

• Premium – The monthly amount you pay to have health insurance.
• Deductible – The amount you pay out of pocket each year before your plan starts paying coinsurance.
• Copay (copayment) – A fixed dollar amount (for example, $25) you pay for certain services, usually at the time of the visit.
• Coinsurance – A percentage of the cost you pay after you meet your deductible.
• Out-of-pocket maximum – The most you’ll pay in a year for covered services. After you hit this limit, the plan generally pays 100% of covered costs for the rest of the year.

How They Compare

How Coinsurance Works Step by Step

Let’s walk through a simple example to make coinsurance more concrete.

Example: Plan With 20% Coinsurance

Imagine your plan looks like this:

• Deductible: $1,500
• Coinsurance: 20% (you) / 80% (plan)
• Out-of-pocket maximum: $6,000

You have a covered medical procedure that the plan’s network rate (allowed amount) sets at $3,000.

1. Apply the deductible

   • If you haven’t paid anything yet this year, you first pay your $1,500 deductible.
   • Remaining amount after deductible: $3,000 − $1,500 = $1,500.

2. Apply coinsurance

   • Your coinsurance is 20%.
   • You pay 20% of the remaining $1,500 = $300.
   • Your plan pays 80% of the remaining $1,500 = $1,200.

3. Total you pay for this procedure

   • Deductible: $1,500
   • Coinsurance: $300
   • Total out-of-pocket for this service: $1,800

4. What counts toward your out-of-pocket maximum?

   • Both your deductible and coinsurance payments (for covered services) usually count.
   • So, $1,800 goes toward your $6,000 out-of-pocket maximum.

If, later in the year, you reach your out-of-pocket maximum, your plan typically pays 100% of covered in-network services for the rest of that plan year.

When Does Coinsurance Apply?

Coinsurance doesn’t apply to every type of service the same way. Plan rules vary, but there are some common patterns.

Common Situations Where Coinsurance May Apply

Coinsurance often applies to:

• Hospital stays (inpatient care)
• Outpatient surgery or procedures
• Advanced imaging (such as CT scans or MRIs)
• Specialist visits after deductible (depending on your plan)
• Emergency room care (sometimes after a copay and deductible)
• Durable medical equipment (crutches, wheelchairs, etc.)
• Some mental health or substance use services

Services That May Use Copays Instead

Some services may use a flat copay instead of coinsurance, especially in many common health plans:

• Primary care visits
• Telehealth visits
• Urgent care visits
• Routine prescriptions
• Some preventive or routine mental health visits

In some plans, you might see a combination—for example:

• A copay for a doctor visit, then
• Coinsurance for lab tests or imaging ordered during that visit

Coinsurance and Network Rules: In-Network vs. Out-of-Network

Your coinsurance percentage can be very different depending on whether you use in-network or out-of-network providers.

In-Network Coinsurance

When you see an in-network provider:

• The insurer has pre-negotiated rates (the “allowed amount”).
• Your coinsurance is based on that lower allowed amount, not whatever the provider originally charged.
• In-network coinsurance percentages are often lower (for example, 10–30%).

Out-of-Network Coinsurance

When you see an out-of-network provider:

• The plan may have a higher coinsurance percentage (for example, 40–50%).
• The provider may bill above the plan’s allowed amount.
• You can sometimes be responsible for:
  1. Your coinsurance on the allowed amount and
  2. The difference between what the provider charges and what the plan allows (this is often called “balance billing”).

Not all plans cover out-of-network care (for example, many HMO or EPO plans), except in emergencies. If out-of-network services are not covered, coinsurance may not apply—you may be responsible for the full bill.

How Coinsurance Affects Your Total Health Care Costs

Coinsurance plays a big role in what you’ll pay during the year, especially if you need a lot of medical care.

Coinsurance and Plan Design

Many health insurance plans balance:

• Higher premiums + lower coinsurance and deductibles
• Lower premiums + higher coinsurance and deductibles

In other words:

• Plans with lower monthly premiums often come with higher coinsurance and deductibles.
• Plans with higher monthly premiums often have lower coinsurance and deductibles.

Which makes sense for you can depend on:

• How often you expect to use medical services
• Whether you have ongoing health conditions
• Your comfort level with larger unexpected bills
• Your ability to handle higher monthly premiums in exchange for lower costs when you need care

Coinsurance and the Out-of-Pocket Maximum

A key protection in many health plans is the out-of-pocket maximum. Once you hit it, your coinsurance usually stops for the rest of the plan year.

This means:

• You won’t pay coinsurance forever; it’s capped by that annual maximum (for covered, in-network services).
• High-cost years (for example, a surgery or major illness) may push you to the maximum quickly. After that, covered in-network care is typically fully paid by the plan.

Understanding “Allowed Amount” and Why It Matters

Coinsurance is almost always calculated on the allowed amount, not the original bill.

• The allowed amount (also called negotiated rate, eligible expense, or contracted rate) is what the insurer has agreed is a reasonable charge for a covered service.
• In-network providers generally accept the allowed amount as full payment, minus your share (deductible, copay, coinsurance).
• Out-of-network providers may charge more than the allowed amount, leaving you responsible for both:
  • Your coinsurance on the allowed amount, and
  • Any balance billing for the difference.

Knowing this helps you understand why using in-network providers often leads to much lower final bills, even with the same coinsurance percentage.

Practical Examples of Coinsurance in Action

Here are a few everyday scenarios to see how coinsurance might show up on your bills.

Example 1: Imaging Test (Deductible Not Met Yet)

• Deductible: $2,000
• Coinsurance: 30%
• Out-of-pocket max: $7,500
• Allowed amount for MRI: $1,200
• Amount you’ve already paid toward your deductible this year: $500

1. Remaining deductible: $2,000 − $500 = $1,500
2. The MRI costs $1,200 (allowed amount), which is less than your remaining deductible.
3. You pay $1,200 for the MRI.
4. No coinsurance applies yet because the deductible is not met.
5. That $1,200 now counts toward your deductible.

Example 2: Surgery After Deductible Is Met

Same plan as above, but now:

• You have already met your $2,000 deductible earlier in the year.
• Allowed amount for surgery: $10,000
• Coinsurance: 30%

You pay 30% of $10,000 = $3,000.
Your plan pays 70% of $10,000 = $7,000.

That $3,000 also counts toward your out-of-pocket maximum.

Coinsurance and Preventive Care

Many health plans waive coinsurance (and deductibles) for certain preventive services when you use in-network providers. These often include:

• Annual wellness visits
• Many routine vaccines
• Certain screening tests (such as some cancer or cholesterol screenings)

For these specific preventive services, your plan may pay 100% of the allowed amount, meaning no coinsurance, no copay, and no deductible. However:

• If a visit is coded as diagnostic rather than preventive (for example, you’re being evaluated for symptoms), your deductible and coinsurance may apply.
• How services are billed and coded can affect whether coinsurance kicks in.

How to Find and Understand Your Coinsurance

To understand your own coinsurance in health insurance, it helps to know exactly where to look and what to ask.

Where to Look

• Summary of Benefits and Coverage (SBC)

  • Usually lists coinsurance for:
    • Primary care visits
    • Specialist visits
    • Emergency room
    • Hospital stays
    • Lab and imaging
  • Look for phrases like “20% coinsurance after deductible.”

• Plan brochure or member portal

  • May break down coinsurance separately for:
    • In-network vs. out-of-network
    • Different service categories (mental health, maternity, rehab, etc.)

• Explanation of Benefits (EOB)

  • After a claim is processed, the EOB shows:
    • Original provider charge
    • Allowed amount
    • What the plan paid
    • Your deductible and coinsurance responsibility

Smart Questions to Ask Your Insurer or HR

When you’re unsure, it can help to call your plan’s customer service or talk with your HR benefits contact. Consider asking:

• What is my in-network coinsurance for:
  • Hospital stays?
  • Outpatient surgery?
  • Imaging (CT, MRI, ultrasound)?
• Does coinsurance apply before or after the deductible for this service?
• What is my out-of-pocket maximum, and how close am I to reaching it?
• How does coinsurance work for out-of-network providers?
• Are there separate deductibles or coinsurance rates for certain types of care (for example, mental health, maternity, or specialty drugs)?

Tips for Managing Costs When Coinsurance Applies

Coinsurance can add up quickly, especially for major procedures. While you can’t change your coinsurance once you’re in a plan year, you can take steps to avoid unnecessary costs.

1. Stay In-Network Whenever Possible

✅ Use in-network doctors, hospitals, and labs to:

• Benefit from lower allowed amounts
• Avoid or reduce balance billing
• Often get lower coinsurance percentages

2. Get Cost Estimates Before Major Care

✅ Before a surgery, imaging test, or other big procedure, ask:

• Is this in-network?
• What is the allowed amount for this service?
• How much of my deductible is left?
• Approximately how much coinsurance will I owe?

Many insurers also offer online tools to estimate your cost for common procedures with different in-network providers.

3. Keep an Eye on Your Year-to-Date Spending

✅ Track how much you’ve paid so far toward:

• Your deductible
• Your out-of-pocket maximum

If you’re close to meeting your out-of-pocket maximum, it may affect when you choose to schedule non-urgent procedures, since your coinsurance may drop to $0 after you reach that limit for the year.

4. Know That Provider Prices Can Vary

Even within the same network, allowed amounts and coinsurance totals may differ by:

• Hospital
• Imaging center
• Surgery center

If you have time and flexibility, asking for estimates from multiple in-network facilities can sometimes lower your final out-of-pocket costs.

Quick Reference: Coinsurance At a Glance

Coinsurance is:

• A percentage of covered costs that you pay
• Usually applied after you meet your deductible
• Based on the plan’s allowed amount for a service
• Capped by your out-of-pocket maximum each plan year

Coinsurance is not:

• Your monthly premium
• Your deductible (that’s a fixed annual amount)
• A copay (that’s a fixed dollar fee per visit or prescription)

Bottom Line: What Coinsurance Means for You

Coinsurance in health insurance is simply your share of covered medical costs after you’ve met your deductible, expressed as a percentage. It works together with your premium, deductible, copays, and out-of-pocket maximum to determine what you’ll pay overall.

Understanding:

• Your coinsurance rate,
• When it starts applying, and
• How it differs in-network vs. out-of-network

can help you plan for medical expenses, compare health insurance plans more confidently, and reduce the chances of unexpected bills.

If you have a specific plan in mind, the most helpful next step is to review your Summary of Benefits and Coverage and, if anything is unclear, ask your insurer or benefits administrator to walk through how coinsurance would apply in real-life situations you care about.