Insurance Appeal Success Rates by Insurer (2024–2025 Data)

Appealing a denied health insurance claim is not a long shot. Across all major insurers, internal appeal overturn rates range from 39% to 75% depending on the plan and denial reason. Yet the overwhelming majority of denied claims — more than 99% according to KFF analysis of ACA marketplace data — are never appealed.

This post breaks down insurer-specific appeal success rates using the most current available data from CMS, state insurance regulators, and independent research. If you are a provider or patient deciding whether to appeal, this data will help you understand your odds and set priorities.

What "Appeal Success Rate" Means

Before diving into numbers, three terms require precise definition:

• Internal appeal overturn rate: The share of internal (first-level) appeals that result in the insurer reversing its denial — fully or partially.
• External appeal overturn rate: The share of IROs) Explained" class="auto-link">independent review organization (IRO) decisions that overturn the insurer's denial, after internal appeal fails.
• Voluntary appeal overturn rate: Appeals the insurer resolves before a formal ruling, often through peer-to-peer physician review.

Most published data covers internal appeals. External appeal data is available from state insurance departments that require IRO reporting (approximately 40 states).

Appeal Success Rates by Major Commercial Insurer

UnitedHealth Group (UHC / Optum)

UHC is the largest commercial insurer in the United States and consistently draws the most denial complaints.

Source: California Department of Managed Health Care (DMHC) Independent Medical Review data, 2022–2023; UHC Annual Report disclosures.

UHC's internal appeal rate is among the lower end for major insurers, but its peer-to-peer success rate is meaningfully higher. Providers who request peer-to-peer review before or during the formal appeal process report better outcomes with UHC than those who submit written appeals alone.

Strategic note: UHC denials for "lack of medical necessity" are most likely to be overturned when the appeal includes a treating physician letter citing UHC's own clinical criteria (available in its Coverage Determination Guidelines, published at uhcprovider.com).

Aetna (CVS Health)

Aetna publishes more granular appeals data than most insurers as part of its CVS Health annual disclosures.

Source: CVS Health regulatory filings; DMHC data; Connecticut Insurance Department annual report, 2023.

Aetna's internal appeal success rate is notably higher than UHC's and Humana's. Aetna also has a structured peer-to-peer program that providers can initiate within 30 days of a prior authorization denial.

Strategic note: Aetna's clinical policy bulletins are publicly available and highly detailed. Appeals that directly address the criteria in the applicable policy bulletin — point by point — have substantially higher overturn rates than generic appeals.

Cigna (The Cigna Group)

Cigna attracted significant regulatory scrutiny in 2023 after a ProPublica investigation revealed that a team of medical reviewers denied claims in batches without reviewing individual records.

Source: ProPublica/STAT News analysis of state insurance data, 2023; DMHC independent medical review data.

Following the 2023 investigation, Cigna entered into settlements in multiple states requiring changes to its review process. Provider-facing policy changes may affect Denial Rates by Insurer (2026)" class="auto-link">denial rates and appeal outcomes in 2024–2025.

Strategic note: Cigna denials frequently cite "not medically necessary per Cigna coverage policy." The most effective appeals for Cigna denials name the specific policy being cited, then demonstrate that the patient's clinical presentation meets each criterion in that policy.

Blue Cross Blue Shield (BCBS — Various Plans)

BCBS operates as 33 independent licensees, so "BCBS" denial and appeal data is highly variable by state. The figures below reflect aggregated data from the largest BCBS plans.

Source: State insurance department annual reports, 2023; CMS Transparency in Coverage data.

BCBS plans that operate in states with stronger consumer protection laws (Illinois, California) consistently show higher overturn rates — in part because state regulators actively review appeal decisions and in part because those plans have developed more structured appeal review processes.

Strategic note: For BCBS appeals, the relevant plan's Medical Policy (searchable at each licensee's provider portal) governs medical necessity determinations. Appeals citing plan-specific medical policy — rather than general clinical guidelines — are more effective.

Humana

Humana is heavily concentrated in Medicare Advantage (it is the second-largest MA insurer) and its denial patterns reflect MA's heightened prior authorization requirements.

Source: OIG Medicare Advantage audit data, 2022; CMS MA appeal data; state insurance filings.

The 61% overturn rate for Medicare Advantage prior authorization appeals is particularly significant. OIG found that a substantial portion of Humana's MA prior authorization denials did not meet Medicare coverage criteria — meaning they were improperly denied in the first place.

Strategic note: For Humana Medicare Advantage appeals, citing the CMS coverage policy (the applicable LCD or NCD) and explicitly stating that the denial does not meet Medicare coverage rules is the single most effective appeal framing. CMS requires MA plans to cover services that traditional Medicare would cover.

Medicare and Medicaid Appeal Success Rates

Traditional Medicare (Fee-for-Service)

Medicare's multi-level appeals process is one of the most robust in U.S. healthcare. CMS publishes detailed data on outcomes at each level.

Medicare FFS Appeal Overturn Rates by Level (2023)

Level 1 — Redetermination (MAC):          ~30%
Level 2 — Reconsideration (QIC):          ~12%
Level 3 — ALJ Hearing:                    ~75%
Level 4 — Medicare Appeals Council:       ~18%
Level 5 — Federal District Court:         ~25%

Source: CMS Medicare Appeals Data, 2023

The dramatic jump at Level 3 (Administrative Law Judge hearing) is well-documented and reflects that ALJs are independent of CMS and apply a preponderance-of-evidence standard. Providers who can demonstrate clinical appropriateness in an ALJ hearing win approximately 3 in 4 cases.

Medicare Advantage Appeals

Source: CMS Medicare Advantage & Part D Appeals Data, 2023.

MA plans overturn a much lower share of initial appeals than traditional Medicare — another reflection of the broader MA denial problem. However, the ALJ hearing success rate (71%) is nearly as high as fee-for-service, making escalation worthwhile for high-value claims.

Medicaid

Medicaid appeal success rates are the least systematically reported. Available data from states with published appeal statistics:

Source: State Medicaid agency annual reports, 2022–2023.

Which Denial Reasons Have the Highest Overturn Rates?

Appeal success varies not just by insurer but by why the claim was denied. The following overturn rates are aggregated across major commercial insurers:

Appeal Overturn Rate by Denial Reason

Medical necessity            ████████████████████ 65%
Experimental/investigational ████████████████░░░░ 55%
Prior auth not obtained      ████████████░░░░░░░░ 43%
Out-of-network               ████████████░░░░░░░░ 41%
Coding/billing error         ██████████████████░░ 60% (via correction/resubmission)
Timely filing                ████░░░░░░░░░░░░░░░░ 18%
Duplicate claim              ██████░░░░░░░░░░░░░░ 22%
Benefit exclusion            █████████░░░░░░░░░░░ 31%

Source: Change Healthcare, AMA, state IRO data

Medical necessity denials are both the most common and among the most winnable on appeal — because the standard for "medical necessity" is defined in the insurer's contract and policy documents, and providers can often demonstrate that the service meets those criteria with proper clinical documentation.

For more detail on each denial type, see The 15 Most Common Reasons Claims Are Denied.

How to Use Appeal Success Rate Data Strategically

For Providers

1. Prioritize appeals by insurer and denial reason. High-value claims denied by Cigna or Aetna for "medical necessity" have the highest expected return on your appeal effort.

2. Request peer-to-peer review for every prior auth denial. Across all major insurers, peer-to-peer review increases overturn rates by 10–20 percentage points over written-only appeals.

3. Track your own appeal data. Practices that track denial reason, insurer, and appeal outcome over time identify patterns that allow targeted process improvements.

4. Do not let timely filing deadlines expire. Timely filing denials have the lowest overturn rate (18%) and are almost entirely preventable.

5. Escalate to external appeal when appropriate. If your internal appeal fails on a high-value claim, External Independent Review: Complete Guide" class="auto-link">external review by an independent organization overturns insurer decisions in roughly 40–48% of cases.

For Patients

1. Always appeal a denial for a significant service. You have nothing to lose and substantial odds of success.

2. Request your insurer's written denial explanation. Federal law (ACA) requires insurers to provide written denial reasons and instructions for appealing. If you do not receive this automatically, request it.

3. Use your state's external appeal rights. All 50 states have some form of external appeal for health insurance denials. Most are free to the patient.

4. Get your doctor involved. Physician-supported appeals succeed at substantially higher rates than patient-only appeals.

How ClaimBack Improves Your Appeal Odds

ClaimBack generates appeal letters calibrated to the specific insurer, denial reason, and clinical context of your case. The system:

• Identifies the insurer's stated denial criteria from its published medical policies
• Structures the appeal response to address each stated denial reason
• Incorporates relevant clinical guidelines (CMS, ClinicalKey, UpToDate summaries) as citations
• Formats the letter to match the administrative requirements of each insurer's appeal department

A well-structured appeal submitted with complete clinical documentation represents your best chance of overturning a denial without escalating to external review or legal action.

Start your appeal letter with ClaimBack — free for your first denial.

Related Resources

• Health Insurance Denial Statistics 2025
• The 15 Most Common Reasons Health Insurance Claims Are Denied
• The Real Cost of Denied Claims to Healthcare Providers
• How to Appeal an Insurance Denial
• Medical Necessity Denial Appeal Guide

Sources

1. KFF. "Claims Denials and Appeals in ACA Marketplace Plans." kff.org, 2023–2024.
2. California DMHC. Independent Medical Review Annual Report, 2023.
3. HHS Office of Inspector General. "Medicare Advantage Organizations Denied Requests That Met Medicare Coverage Rules." OEI-09-18-00260, 2022.
4. CMS. Medicare Fee-for-Service Appeals Data, 2023. cms.gov.
5. CMS. Medicare Advantage & Part D Appeals and Grievances Data, 2023.
6. ProPublica/STAT News. "Cigna Rejected Health Insurance Claims Using Algorithm." March 2023.
7. Connecticut Insurance Department. Annual Report on Health Insurance Complaints and Appeals, 2023.
8. Change Healthcare. "2022 Revenue Cycle Denials Index."
9. American Medical Association. "2023 Prior Authorization Physician Survey."