Patient Responsibility

Medicare Coinsurance: Why You Owe 20%

Name: Medicare Coinsurance: Why You Owe 20%
Creator: Barley Billing Team
Published: 2026-03-26

Written by Barley Billing Team, Medicare Billing Experts | Last reviewed March 26, 2026

Does your notice say something like this?

"Coinsurance amount"

"You are responsible for the coinsurance"

"Your share of the cost"

If so, you're in the right place. Here's what it means and what to do.

What This Means

Your Medicare Summary Notice or Explanation of Benefits shows a “coinsurance” amount. This is not a denial. Medicare approved your claim and paid its share — the coinsurance is the portion you owe.

For most Part B services (doctor visits, outpatient care, medical equipment), Medicare pays 80% of the approved amount and you pay the remaining 20%. This 20% is your coinsurance.

Why This Happens

This is standard Medicare cost-sharing. After you meet your annual Part B deductible ($283 in 2026), you pay 20% coinsurance on most Part B services. This is how Original Medicare is designed.
There is no annual cap on coinsurance in Original Medicare. Unlike Medicare Advantage plans, Original Medicare does not have an out-of-pocket maximum. If you have many or expensive services, your coinsurance can add up throughout the year.
Part A has different coinsurance rules. For hospital stays, you pay nothing for days 1-60 (after the deductible), then a daily coinsurance for days 61-90 ($446 per day in 2026), and a higher amount for lifetime reserve days.

Should You Appeal?

This is not a denial

Coinsurance is a standard part of Medicare cost-sharing and is not appealable. Medicare approved the service and paid its portion — the coinsurance is your share.

However, you should verify the amount is correct. If the coinsurance seems too high, check that the underlying service was billed accurately and that Medicare applied the correct approved amount.

What To Do Next

Verify the amount. Check that the coinsurance is 20% of the Medicare-approved amount (not the provider’s full charge). The approved amount should be listed on your Medicare Summary Notice.
Check if you have supplemental coverage. If you have a Medigap (Medicare Supplement) policy, it likely covers some or all of your Part B coinsurance. Most Medigap plans (A, B, D, F, G, K, L, M, N) cover Part B coinsurance at 50% to 100%. Contact your Medigap insurer to file a claim.
Look into Medicare Savings Programs. If you have limited income, you may qualify for a Medicare Savings Program that helps pay coinsurance. Contact your State Health Insurance Assistance Program (SHIP) at shiphelp.org or call 1-800-MEDICARE.
If you’re having trouble paying, ask your provider about payment plans. Many providers offer interest-free payment arrangements for Medicare patients.
Consider Medigap for future protection. If you are in Original Medicare and do not have supplemental coverage, a Medigap policy can protect you from high coinsurance costs. Note that the best time to enroll is during your Medigap Open Enrollment Period.

Sources

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Frequently Asked Questions

Is this a denial?

No. A coinsurance charge means Medicare approved and paid its share of your claim. The coinsurance is the portion you are responsible for — typically 20% of the Medicare-approved amount for Part B services.

Why is my coinsurance so high?

Coinsurance is a percentage, not a flat fee. If you had an expensive service — such as an MRI, surgery, or extensive lab work — 20% of a large bill can be a significant amount. There is no annual cap on Part B coinsurance in Original Medicare.

Can I get help paying my coinsurance?

Yes. Medigap (Medicare Supplement) plans cover Part B coinsurance — most cover 100% of it. Medicaid may also cover coinsurance if you qualify. Additionally, some Medicare Savings Programs help low-income beneficiaries with cost-sharing.

Does Medicare Advantage handle coinsurance differently?

Yes. Medicare Advantage plans may charge copays instead of coinsurance for some services, and they have an annual out-of-pocket maximum (capped at $9,250 in 2026). Original Medicare has no out-of-pocket maximum.

Not Sure If Your Bill Is Right?

Send us your bill or Medicare notice and we'll check it for free. If there's an error, we'll tell you exactly what it is and what to do about it.

This information is for educational purposes only and is not legal or medical advice. Always verify with your doctor's office and insurance company.