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The average insurance denial rate across major health insurers is approximately 26%, meaning 1 in 4 claims are denied on first submission. However, more than half of denials are overturned on appeal.
See how often major insurers deny claims, which denials get overturned, and what you can do when it happens to you. Data sourced from CMS transparency reports.
1 in 4 claims get denied on first submission. But here's what most people miss: over half of those denials get overturned on appeal. Most patients never appeal because they assume it won't work. The numbers say otherwise.
| Insurer | Denial Rate | Appeal Success |
|---|---|---|
| UnitedHealthcare | 32% | 51% |
| Anthem/Elevance | 28% | 47% |
| Aetna (CVS Health) | 26% | 53% |
| Cigna | 24% | 55% |
| Humana | 22% | 49% |
| Blue Cross Blue Shield (Avg) | 25% | 52% |
| Kaiser Permanente | 18% | 58% |
Data Source: Aggregated from CMS transparency reports, state insurance department filings, and insurer-reported data. Denial rates vary by plan type and may not reflect your specific experience. Updated quarterly.
The insurer says your treatment wasn't medically necessary based on their internal rules — even when your own doctor disagrees.
How to appeal: Get a letter from your doctor explaining why the treatment IS medically necessary, citing clinical guidelines and your specific medical history.
You got treatment without getting pre-approval first. Usually the provider's mistake, but the bill lands on you.
How to appeal: Argue that the prior authorization requirement wasn't clearly communicated, or that it was an emergency situation where prior auth wasn't feasible.
Your provider wasn't in your plan's network. This can hit you even when you thought they were covered.
How to appeal: Check if the No Surprises Act applies (emergency care, surprise billing). Request network adequacy review if no in-network providers were available.
Your plan doesn't cover this particular service or treatment.
How to appeal: Review your Summary of Benefits. If the denial is incorrect, cite specific policy language. If it's experimental, provide clinical evidence of efficacy.
Incorrect procedure codes, typos, or missing information on the claim form.
How to appeal: Have your provider correct and resubmit the claim with proper coding. These denials are usually easy to overturn.
Key Takeaway: Administrative denials (coding errors, missing prior auth) are most likely to be overturned. "Not medically necessary" denials require stronger clinical evidence but are still winnable 45% of the time with a good appeal letter.
More insurers now use AI to auto-review claims, which means more auto-denials based on pattern matching — not individual circumstances. Some Medicare Advantage plans have been caught running AI that denies claims far more aggressively than human reviewers ever did.
The list of services that need prior authorization keeps growing. Treatments that used to get approved automatically now require a pre-approval process, and skipping that step means a denied claim.
As healthcare costs climb, insurers deny more claims to protect their margins. Internal metrics can reward reviewers for higher denial rates, especially when insurers know most patients won't bother to appeal.
Medical billing now involves thousands of diagnosis and procedure codes. A single typo or code mismatch triggers an automatic denial, and it's the patient who has to figure out what went wrong.
Federal law (ACA) gives you the right to appeal any denial. Your insurer must:
Professional appeal letter service with 70%+ success rate
Step-by-step guide to appealing insurance denials
Legal precedents from insurance denial class action lawsuits
Understand your healthcare rights under federal law
The average in-network claim denial rate across major insurers is approximately 17%, according to KFF analysis of ACA marketplace plans. However, rates vary significantly by insurer: some deny fewer than 10% of claims while others deny over 30%. Prior authorization denials tend to be even higher, with some insurers denying 25-40% of prior auth requests.
The top denial reasons are: lack of prior authorization (28% of denials), services deemed not medically necessary (24%), out-of-network provider (18%), coding or billing errors (15%), and missing information or documentation (10%). Many of these denials are reversible on appeal with proper documentation.
Start by requesting a written explanation of the denial reason and your plan documents. File an internal appeal within 180 days of the denial notice, including supporting medical records and a letter from your physician explaining medical necessity. If the internal appeal is denied, you have the right to an external review by an independent third party under the ACA.
Internal appeals succeed approximately 40-50% of the time when properly documented. External reviews overturn denials in about 40-60% of cases. Despite these favorable odds, fewer than 1% of denied claims are actually appealed by patients, representing billions in unclaimed benefits annually.
Yes. You have the right to appeal any prior authorization denial. Your physician can request a peer-to-peer review with the insurance company medical director, which overturns approximately 60-75% of initial denials. Expedited appeals are available for urgent medical situations and must be resolved within 72 hours.
Yes. Under the ACA Transparency in Coverage rule, insurance companies must publicly report their claims denial rates, appeal rates, and overturn rates. CMS publishes this data annually for marketplace plans. Some states have additional transparency requirements for employer-sponsored and Medicaid managed care plans.
Surprise billing occurs when you receive unexpected charges from out-of-network providers during emergency care or at in-network facilities. The No Surprises Act (effective January 2022) protects patients by capping out-of-network charges at in-network rates and establishing an independent dispute resolution process between providers and insurers.
Most appeals do not require a lawyer. Internal and external appeals can be filed by patients or their physicians directly. However, for complex cases involving high-dollar claims, experimental treatments, or systematic denial patterns, a patient advocate or healthcare attorney can significantly improve outcomes. Many patient advocacy organizations offer free assistance.
Gather your complete medical records including clinical notes, test results, and imaging reports. Obtain a letter of medical necessity from your treating physician, your insurance plan documents (Summary of Benefits), the denial letter with specific reason codes, and any peer-reviewed studies supporting the treatment. Organized documentation is the single biggest factor in appeal success.
Under federal law, insurers must resolve standard internal appeals within 30 days for pre-service claims and 60 days for post-service claims. Urgent care appeals must be resolved within 72 hours. External reviews by independent organizations must be completed within 45 days. If your insurer misses these deadlines, the denial is automatically overturned in many states.
Data Disclaimer: Denial rates and statistics are aggregated from publicly available data including CMS transparency reports, state insurance department filings, and insurer-reported data. Rates vary by plan type, state, and individual circumstances. This information is for educational purposes and does not constitute legal or medical advice. For specific questions about your coverage or denials, contact your insurer or consult with a qualified professional.