Patients who appeal denied health insurance claims win more often than they lose—but the success rate varies dramatically by insurance type and appeal level. Medicare Advantage appeals succeed about 81% of the time, external appeals overturn roughly half of all denials, and the trend is improving; however, ACA marketplace appeals reverse only about one-third of denials, making the headline less universal than it appears.
The real problem is not success rates but participation. Fewer than 1% of ACA marketplace claim denials are appealed, and only 11.5% of Medicare Advantage prior authorization denials are contested. Most patients either don't know they can appeal, miss the deadline, or give up without trying—meaning millions of dollars in rightfully covered care go unfunded every year because people never pushed back.
Table of Contents
- Why Appeals Win So Often
- Success Rates Differ Sharply by Insurance Type and Appeal Level
- Mental Health and Substance Abuse Appeals Succeed Most
- Lower-Income Patients Have Lower Overturn Rates
- How to Appeal Your Denial
- Frequently Asked Questions
Why Appeals Win So Often
When an insurance company denies a claim initially, the decision is often made quickly and without the full medical picture. Appeals work because they force a second look, allow your doctor to submit missing evidence, and require the insurer to apply its own coverage rules correctly.
According to Kaiser Family Foundation analysis of 2024 Medicare Advantage data, insurers fully or partially overturned 80.7% of prior authorization denials that were appealed. This means the initial denial was often wrong, incomplete, or based on insufficient information. The gap between initial denial rates and appeal overturn rates reveals a pattern: insurers deny roughly 19% of in-network claims to begin with, partly as a business practice that shifts the burden to patients and providers to push back. When someone actually appeals, the insurer must justify the denial against medical evidence, and frequently cannot.
Success Rates Differ Sharply by Insurance Type and Appeal Level
Medicare Advantage and commercial insurance follow different rules, which explains why your odds depend on what type of plan you have. Medicare Advantage prior authorization appeals—decisions about whether a treatment is medically necessary—reverse 80.7% of the time, making them your strongest bet.
ACA marketplace appeals tell a different story: only about 34% of appealed denials are reversed, suggesting these plans may make more careful initial decisions or apply stricter standards. The highest odds come at the final appeal level.
External review—where an independent physician outside the insurance company evaluates your case—overturns denials at substantially higher rates than the insurer's own internal review, with national rates climbing from 38% in 2019 to over 52% in 2025. This suggests that independent review breaks insurer bias and that many denials cannot withstand scrutiny from someone with no financial stake in rejecting your claim.
Mental Health and Substance Abuse Appeals Succeed Most
Not all medical services appeal equally. Mental health and substance abuse treatment denials overturn at rates around 60–61%, higher than most other services. This may reflect that insurers initially deny mental health care based on thin evidence about medical necessity, or that these categories trigger stricter review on appeal. Geographic location and your specific insurer also matter.
In published data, external appeal overturn rates for individual insurers ranged from 36% to 85%—a gap reflecting different underwriting standards and whether the plan requires clear medical evidence upfront. If your state publishes appeal data (as New York does), look up your insurer's numbers before appealing, as it will give you realistic odds.
Lower-Income Patients Have Lower Overturn Rates
Income affects whether an appeal succeeds. Among denied claims from 2017–2019, households earning under $50,000 annually had approximately 48% of appeals overturned, compared to 52% for households earning over $100,000. The gap is modest but real, suggesting that lower-income patients may have less access to legal help, less time to gather documentation, or less ability to navigate complex appeal processes.
The income disparity compounds the broader appeal problem: very few people appeal at all, but lower-income patients may be even less likely to know they can appeal, or may lack the bandwidth while managing medical debt. If you earn less and face a significant denial, appealing may be one of the few tools within your control to reduce your out-of-pocket cost.
How to Appeal Your Denial
Start with your insurance company's appeal form, available on its website or by calling the number on your card. Most plans require appeals within 30–60 days of the denial, so act quickly. You do not need a lawyer, and the appeal itself is free. Strengthen your appeal by including anything new: recent medical records your doctor can send, a letter from your physician explaining why the treatment meets the plan's own criteria for coverage, or documentation that you meet eligibility requirements.
Many insurers reverse denials on appeal simply because they see information they overlooked the first time. If the internal appeal is denied, request external review. Your insurance company is required by law to explain how. External review is your strongest option and succeeds significantly more often than internal review alone.
Frequently Asked Questions
Do I need a lawyer to appeal a health insurance denial?
No. You can appeal on your own without a lawyer and at no cost to yourself. However, a lawyer who specializes in insurance appeals can improve your odds, especially if the claim is large or complex.
How long do appeals take?
Internal appeals typically take 30–60 days. External review can take longer—sometimes 60 days or more—but has higher overturn rates.
If my appeal is denied, can I appeal again?
Yes. If your insurer denies your internal appeal, you have the right to request external review by an independent physician. This is your final appeal option before seeking legal action.