UNH Prior-Auth Denials at 17%, Centene 25%: New KFF Transparency Data

For investors in managed care, CMS's first mandatory prior authorization dataset creates a new operational metric for evaluating public plan insurers. UnitedHealth Group's 17% Medicare Advantage denial rate and Centene's 25% ACA Marketplace rate stand out as potential liability markers, while Elevance's 5% and GuideWell's 3% rates may signal more provider-friendly claims operations.

On August 14, 2026, KFF released its first analysis of newly mandated prior authorization data from the nation's major government-subsidized insurance programs, revealing that health insurers denied at least one in eight standard prior authorization requests in 2025. Across Medicare Advantage, Medicaid managed care, and Affordable Care Act Marketplace plans, standard requests were denied at overall rates of 12 percent for Medicare Advantage and 18 percent for ACA Marketplace coverage. The figures mark the initial baseline under a 2026 Centers for Medicare & Medicaid Services transparency rule that requires insurers to publicly report prior authorization metrics.

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UnitedHealth Group's 17% Medicare Advantage denial rate and Centene's 25% ACA Marketplace rate stand out as potential liability markers, while Elevance's 5% and GuideWell's 3% rates may signal more provider-friendly claims operations.

The report found dramatic variation among insurers that operate in the same programs. In Medicare Advantage, standard denial rates for the largest plans ranged from 5 percent at Elevance to 17 percent at UnitedHealth Group. In Medicaid managed care, L.A. Care Health Plan denied 2 percent of standard requests while Independence Health Group denied 23 percent. In ACA Marketplace plans, GuideWell denied just 3 percent while Centene denied 25 percent. Expedited requests, which are supposed to be processed for urgent needs, were denied at similar or slightly lower rates, indicating that even time-sensitive care faced substantial friction in some plans.

The data are significant because they are the first to be published under CMS's 2026 reporting mandate, a federal effort to make prior authorization practices more transparent and comparable. Overall, most requests were approved—between 82 percent and 90 percent depending on plan type—yet a 12 to 18 percent denial rate translates into millions of delayed or blocked services across three programs that cover tens of millions of Americans. The wide gap between the lowest and highest denial rates suggests that some insurers may be applying more restrictive clinical review criteria or relying more heavily on automated decisioning, while others take a more permissive approach.

The most striking finding is what happens on appeal. The KFF analysis found that 67 percent of denied Medicare Advantage prior authorization requests were overturned when appealed, along with 47 percent in Medicaid managed care and 43 percent in ACA Marketplace plans. The fact that most appeals reverse the initial denial raises serious questions about the accuracy and fairness of the initial review process. However, appeals remain rare, which means many patients and providers may simply absorb the denial or abandon care rather than contest it. Industry group AHIP said median response times for standard requests are about one day, much faster than federal timeframes, and emphasized that the vast majority of requests are approved quickly.