What Is Coinsurance?

Coinsurance is the percentage you pay for a covered health care service after you have met your deductible. If your plan says "20% coinsurance," you pay 20% of the allowed amount and your plan pays 80%, but only after you have satisfied your deductible. Before that, you pay the full allowed amount yourself.

What coinsurance means

The official definition from HealthCare.gov^[1] is: "The percentage of costs of a covered health care service you pay (20%, for example) after you've paid your deductible."

The word to notice is percentage. That distinguishes coinsurance from a copay, which is a flat dollar amount. A copay is $30 whether the underlying visit costs $100 or $500. Coinsurance moves with the cost, so it can be trivial on cheap care and substantial on expensive care.

Coinsurance, deductible, copay, and premium: the four pieces

These four terms are the building blocks of what you pay, and they are easy to confuse. Here is each, from the HealthCare.gov glossary^[2]:

The deductible and coinsurance usually work in sequence. You pay the first dollars yourself until you reach the deductible, and after that you pay your coinsurance percentage while the plan pays its share. A copay can apply either before or after the deductible, depending on the plan and the service.

How coinsurance works after your deductible

The simplest example, from HealthCare.gov^[1]: a doctor visit has an allowed amount of $100 and your plan charges 20% coinsurance.

• If you have already met your deductible, you pay $20 and the plan pays $80.
• If you have not met your deductible, you pay the full $100.

This one rule explains most of the confusion. People read "20% coinsurance" and expect a $20 bill on a $100 visit, then are surprised when they owe the whole $100 early in the year. The missing variable is the deductible, and whether it has been met yet.

Common coinsurance splits, worked out

The numbers after a coinsurance split are always "plan pays first, you pay second." Here is what you owe after your deductible at the most common splits, across different bill sizes:

The 80/20 split is one of the most common, and 90/10 and 70/30 are also typical. The first number is always the plan's share, the second is yours.

A full year, worked through

Here is a complete year, using the example figures HealthCare.gov^[1] provides. Suppose your covered costs for the year total $12,000, your deductible is $3,000, and your coinsurance is 20%.

First you pay the $3,000 deductible. That leaves $9,000. You pay 20% of that remaining $9,000, which is $1,800, and the plan pays the other $7,200. Your total for the year is $4,800, the deductible plus your coinsurance share.

If your plan's out-of-pocket maximum is reached along the way, the plan takes over at 100% and your spending stops there.

Coinsurance and your out-of-pocket maximum

Your coinsurance payments count toward your out-of-pocket maximum, alongside your deductible and copays. The 2026 limit for a Marketplace plan is no more than $10,600 for an individual and $21,200 for a family^[3]. Once your deductible, copays, and coinsurance for in-network covered care add up to that number, your plan pays 100% of covered services for the rest of the year.

The out-of-pocket maximum is the safety net that makes coinsurance manageable on a bad year. A 20% share of a $200,000 hospital admission would be $40,000 on its own, but the out-of-pocket maximum caps it well below that.

Medicare is the important exception to this logic, covered below, because Original Medicare has no out-of-pocket maximum at all.

Coinsurance in real situations

Coinsurance applies unevenly depending on what kind of care you get:

• An office visit might carry a flat copay instead of coinsurance, especially before the deductible is met.
• Lab work and imaging often carry coinsurance, which is why an MRI can cost you hundreds even after a small copay at the doctor.
• Surgery and hospital stays are where coinsurance matters most, because the bills are large and 20% of a large bill is a large amount.
• Prescription drugs often sit on their own tier with their own copays or coinsurance, separate from medical care.

Medicare coinsurance

Original Medicare uses coinsurance differently from private plans, and it is worth knowing the 2026 numbers exactly.

Medicare Part B, which covers doctor visits and outpatient care, has a $283 annual deductible in 2026^[4], after which you usually pay 20% of the Medicare-approved amount for most services. The standard Part B premium is $202.90 a month in 2026.

Medicare Part A, which covers hospital stays, has a $1,736 deductible per benefit period in 2026^[5], then daily coinsurance for long stays: $434 per day for days 61 through 90, and $868 per day for lifetime reserve days after day 90.

The key difference from private insurance is that Original Medicare has no out-of-pocket maximum. There is no yearly cap on what you can pay, which is why many people buy a Medicare Supplement (Medigap) policy to cover the coinsurance they would otherwise owe.

Common mistakes people make

• Assuming coinsurance applies from the first dollar. It does not; the deductible comes first.
• Confusing coinsurance with copay. One is a percentage, the other is a flat dollar amount.
• Forgetting that coinsurance scales. 20% sounds small until it applies to a $50,000 bill.
• Assuming every service uses coinsurance. Many visits use a flat copay instead, and preventive care is often covered at 100% before the deductible.
• Not checking whether the coinsurance applies in or out of network. Out-of-network care usually costs much more and may not count toward the out-of-pocket maximum.

Frequently asked questions

What does coinsurance mean on my health insurance? Coinsurance is the percentage of a covered service you pay after meeting your deductible, defined by HealthCare.gov^[1]. A 20% coinsurance means you pay 20% and the plan pays 80%.

What does 20% coinsurance mean? You pay 20% of the allowed amount for a covered service, and the plan pays 80%. On a $100 visit you pay $20. The 20% starts only after you meet your deductible.

Do I pay coinsurance before or after my deductible? After. Until you meet your deductible you generally pay the full allowed amount. Coinsurance begins once the deductible is met (HealthCare.gov^[1]).

What is coinsurance after deductible? It is your percentage share of each covered service once the deductible is satisfied. If your coinsurance is 20%, you pay 20% of each service's allowed amount and the plan pays 80% (HealthCare.gov^[1]).

Is coinsurance better than a copay? Neither is universally better. A copay is predictable, which is safer on expensive care. Coinsurance scales with cost, so it is cheaper on cheap care and heavier on expensive care.

What is the difference between a deductible and coinsurance? The deductible is the upfront amount you pay before the plan pays anything. Coinsurance is the percentage you pay after meeting the deductible (HealthCare.gov^[2]).

What is the difference between a deductible and an out-of-pocket maximum? The deductible is what you pay before the plan starts paying. The out-of-pocket maximum is the most you pay all year for covered in-network care, after which the plan pays 100% (HealthCare.gov^[3]).

What is Medicare Part B coinsurance? For most Part B services, you pay 20% of the Medicare-approved amount after meeting the $283 annual deductible in 2026^[4]. Original Medicare has no out-of-pocket maximum.

Does coinsurance count toward my out-of-pocket maximum? Yes. Deductibles, copays, and coinsurance for covered in-network care all count. Premiums, out-of-network care, and uncovered services do not (HealthCare.gov^[6]).

Why did my bill show I owe the full amount instead of 20%? Because you likely had not yet met your deductible. Before the deductible is met, you pay the full allowed amount rather than just your coinsurance share (HealthCare.gov^[1]).

This is patient education, not financial or legal advice. Figures are tied to their primary sources and year, because deductibles, coinsurance, and out-of-pocket limits change every plan year. Reviewed October 3, 2026.

Sources

• HealthCare.gov, Coinsurance^[1]
• HealthCare.gov, Deductible^[2]
• HealthCare.gov, Out-of-pocket maximum/limit^[3]
• HealthCare.gov, Out-of-pocket costs^[6]
• Medicare.gov, Medicare costs^[4]
• Medicare.gov, What does Medicare cost^[5]