Quick Answer
In 2024, HealthCare.gov marketplace insurers denied 19% of in-network claims (about 85 million claims), yet consumers appealed fewer than 1% of those denials. When people did appeal, insurers overturned roughly 1 in 3 internal appeals — and in Medicare Advantage, 80.7% of appealed prior-authorization denials were overturned. The lesson in the data: denials are common, appeals are rare, and appeals work. Every figure on this page is cited to KFF/CMS public data.
Last updated: 2026-07-01 · Source: AppealArmor analysis of public KFF/CMS data · About the authors
Research · 2024 data
What the public data says about how often U.S. health insurers deny claims, how rarely people fight back, and how often those who do, win.
Three numbers tell the story of U.S. health-insurance denials. Insurers on the ACA marketplace denied 19% of in-network claims in 2024. Of those roughly 85 million denied claims, consumers appealed fewer than 1%. And of the internal appeals that were filed, insurers overturned about 34% (they upheld 66%).
The gap between how often claims are denied and how often denials are challenged is enormous — and it matters, because the data shows appeals succeed at meaningful rates. In Medicare Advantage, where the numbers are especially stark, 80.7% of appealed prior-authorization denials were overturned in 2024. A denial is the start of a negotiation, not the end of one.
Every figure links to its public source. Marketplace figures come from KFF's analysis of the CMS Transparency in Coverage Public Use File; Medicare Advantage figures from KFF's analysis of CMS prior-authorization data.
| Figure | What it measures | Source |
|---|---|---|
| 19% | Average in-network claim denial rate for HealthCare.gov marketplace insurers | KFF, 2024 |
| ~85 million | In-network claims denied by HealthCare.gov marketplace insurers | KFF, 2024 |
| <1% | Share of denied in-network claims that consumers appealed (at least 262,982 appeals) | KFF, 2024 |
| 66% | Share of appealed denials that insurers upheld on internal appeal (i.e. ~34% were overturned) | KFF, 2024 |
| 5,881 | External (independent) appeals filed by marketplace enrollees — the external overturn rate is suppressed in the public data | KFF, 2024 |
| 52.8 million | Prior-authorization determinations made by Medicare Advantage insurers | KFF, 2024 |
| 7.7% | Share of Medicare Advantage prior-authorization requests fully or partially denied (about 4.1 million) | KFF, 2024 |
| 11.5% | Share of denied Medicare Advantage prior-authorization requests that were appealed | KFF, 2024 |
| 80.7% | Share of appealed Medicare Advantage prior-authorization denials that were overturned | KFF, 2024 |
Share of 2024 HealthCare.gov in-network denials by reported reason. Note that the single largest category is "other / not specified," a transparency gap KFF highlights. Source: KFF, 2024.
When an internal appeal fails, federal law gives most plan members a second shot: an independent external review by a reviewer with no ties to the insurer, whose decision is binding on the plan (45 CFR 147.136; HealthCare.gov). Yet marketplace enrollees filed only 5,881 external appeals in 2024 — a rounding error against 85 million denials.
Federal rules generally give you up to four months after a final internal denial to request external review. It is one of the most powerful — and least used — consumer protections in American health insurance.
These are infrastructure constants from our knowledge base — the evidence library our appeal letters draw on — not outcome claims. Source: AppealArmor statistics API.
This report is free to cite and share under CC BY 4.0 with attribution to AppealArmor. Figures verified against the linked public sources on 2026-07-01.
AppealArmor turns your denial letter into an evidence-based appeal — citing the legal authorities and clinical standards that get denials overturned.
Start My Appeal — Free