Every year, US health insurers deny hundreds of millions of claims. Most patients accept the denial without knowing that the majority of appeals succeed. This page compiles the most current data on denial rates, appeal outcomes, prior authorization statistics, and insurer-specific figures — sourced from KFF, the American Medical Association, CMS, and peer-reviewed research.
US health insurers deny approximately 17% of in-network claims on average across ACA marketplace plans, with individual insurer rates ranging from under 5% to over 40% depending on the plan and state.
KFF Analysis of CMS Data, 2023Denial rates vary enormously across insurers, states, and plan types. The following data covers ACA marketplace plans, which are required to report denial data to CMS.
| Metric | Value | Source |
|---|---|---|
| Average in-network denial rate (ACA marketplace) | 17% | KFF / CMS, 2023 |
| Lowest insurer denial rate (ACA marketplace) | <5% | KFF, 2023 |
| Highest insurer denial rate (ACA marketplace) | >40% | KFF, 2023 |
| Total ACA marketplace claims denied (2022) | 49 million | KFF / CMS, 2022 |
| Total US claims denied annually (all plan types) | ~850 million | Industry estimates, 2024 |
| Denial rate for out-of-network claims | Significantly higher | CMS, 2023 |
| Denial rate for experimental/investigational treatments | 25–35% | Commonwealth Fund, 2023 |
CMS requires ACA marketplace insurers to report denial data. Self-funded employer plans (governed by ERISA) are not required to publicly report denial rates — meaning real total denial numbers are significantly higher than publicly available data suggests. The 850 million annual denial estimate includes employer plan data from industry sources.
Patients win approximately 59% of internal insurance appeals they formally file. For medical necessity denials with complete clinical documentation, overturn rates reach 70–83%. Less than 1% of patients eligible to appeal actually do so.
KFF, 2023| Appeal Type | Overturn Rate | Source |
|---|---|---|
| Internal appeal (all denial types) | 59% | KFF ACA Marketplace Analysis, 2023 |
| Medical necessity denial with full clinical documentation | 70–83% | KFF / AMA, 2023–2024 |
| Prior authorization appeal with peer-to-peer review | 70–83% | AMA Prior Authorization Survey, 2024 |
| External review (independent review organization) | 40–60% | KFF External Review Analysis, 2023 |
| Patients who file a formal appeal (% of eligible) | <1% | KFF, 2023 |
| Patients who request external review (% of eligible) | <0.2% | KFF, 2023 |
The gap between the appeal success rate (59–83%) and the percentage of patients who appeal (<1%) represents the single largest opportunity in US healthcare advocacy. The majority of denied claims are potentially reversible — the barrier is awareness and access to the appeal process, not the merit of the claims.
94% of US physicians report that prior authorization requirements delay patient care. Prior authorization denial rates average 6–12% across major insurers, with specialty medications and procedures significantly higher. Physicians spend an average of 13 hours per week on PA requirements.
AMA Prior Authorization Physician Survey, 2024| Metric | Value | Source |
|---|---|---|
| Physicians reporting PA delays patient care | 94% | AMA PA Survey, 2024 |
| Physicians reporting PA negatively impacts outcomes | 89% | AMA PA Survey, 2024 |
| Average physician hours per week on PA requirements | 13 hours | AMA PA Survey, 2024 |
| Average PA denial rate (all insurers) | 6–12% | CMS / KFF, 2023 |
| PA denials overturned when formally appealed | 83% | KFF, 2023 |
| Physicians who abandoned treatment due to PA denial | 78% | AMA PA Survey, 2024 |
| Patients who experienced serious adverse event due to PA delay | 24% | AMA PA Survey, 2024 |
| Medicare Advantage PA denial rate (2022) | 6.8% | HHS OIG Report, 2022 |
| Medicare Advantage PA denials meeting coverage criteria | 18% | HHS OIG Report, 2022 |
A 2022 HHS Office of Inspector General report found that 18% of Medicare Advantage prior authorization denials met Medicare coverage criteria — meaning nearly 1 in 5 PA denials were incorrectly denied and should have been approved under the plan’s own rules. This finding triggered increased CMS oversight of Medicare Advantage prior authorization practices.
Denial rates vary dramatically by insurer. In ACA marketplace data, some insurers deny over 40% of claims while others deny under 5%. UnitedHealthcare, Cigna, and their subsidiaries consistently rank among higher-denial insurers in AMA physician surveys on prior authorization burden.
KFF Analysis of CMS Data, 2023; AMA PA Survey, 2024| Insurer | AMA PA Burden Ranking | Notable Data Point |
|---|---|---|
| UnitedHealthcare | High | Largest US insurer by enrollment; highest PA volume by absolute count; subsidiary companies include Oxford, UMR, and others |
| Cigna / Evernorth | High | Consistently cited in AMA surveys for high PA burden; 2023 lawsuit over automated denial systems |
| Aetna / CVS Health | High | High prior authorization denial rates; publicly accessible Clinical Policy Bulletins define coverage criteria |
| BlueCross BlueShield | Moderate–Variable | 34 independent regional plans with widely varying denial rates; some BCBS plans have very low denial rates |
| Humana | Moderate | Higher denial rates in Medicare Advantage; HHS OIG audit identified compliance concerns |
| Molina Healthcare | Variable | Medicaid-focused; denial rates vary significantly by state contract |
Note: Insurer-specific denial rate data for self-funded employer plans is not publicly reported. The table above reflects ACA marketplace and Medicare Advantage data where available, supplemented by AMA physician survey data on prior authorization burden.
Insurance denials have measurable health consequences. 26% of insured US adults report being denied coverage for a needed service in the past year. One-third of denied patients delay or forgo care entirely, and 24% of physicians report a patient experienced a serious adverse event due to a prior authorization delay.
Commonwealth Fund Health Care Survey, 2023; AMA PA Survey, 2024| Impact Metric | Value | Source |
|---|---|---|
| Insured adults denied coverage for needed service (past year) | 26% | Commonwealth Fund, 2023 |
| Denied patients who delayed or skipped care | ~33% | Commonwealth Fund, 2023 |
| Patients who paid out of pocket after denial | ~40% | KFF Health Tracking Poll, 2023 |
| Physicians reporting patient serious adverse event from PA delay | 24% | AMA PA Survey, 2024 |
| Patients who gave up on appealing due to complexity | ~35% | Commonwealth Fund, 2023 |
| Average out-of-pocket cost when denial not appealed | Varies widely | KFF, 2023 |
External review — conducted by an independent organization after a failed internal appeal — overturns insurer decisions in approximately 40–60% of cases. The external reviewer’s decision is legally binding on the insurer. Fewer than 0.2% of eligible patients request external review.
KFF External Review Analysis, 2023| Metric | Value | Source |
|---|---|---|
| External review overturn rate | 40–60% | KFF, 2023 |
| Cost to patient for external review | Free | ACA federal law |
| External review decision binding on insurer | Yes — legally required | ACA, ERISA |
| Standard external review decision timeline | 45–60 days | ACA regulations |
| Expedited external review decision timeline | 72 hours | ACA regulations |
| Patients requesting external review (% of eligible) | <0.2% | KFF, 2023 |
The data is clear: most appeals succeed, but fewer than 1% of patients file one. AppealGen generates a professionally structured appeal letter in 10 minutes — tailored to your specific denial reason and insurer. Free to start.
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