ACA insurers worst offenders for prior authorization denials, with rates averaging 18%: KFF

By Chad Van Alstin / August 19, 2026

Despite regulations aimed at making the prior authorization process more transparent, insurers across the board still deny standard requests for patient care coverage 12% to 18% of the time, a new report from KFF revealed.

Using claims data from 2025, KFF’s analysis showed that Medicare Advantage plans were not at the forefront of denials. In fact, they had the lowest denial rate, at 12%, followed by Medicaid managed care plans at 14% and ACA marketplace plans at 18%, respectively.

Data used in the analysis came from roughly 71 million enrollees working through 14 medical payer groups. When zooming in on individual companies offering Medicare Advantage plans, the most likely to deny a standard prior authorization request was UnitedHealthcare, at a rate of 17%.

While competitor Centene was less likely to deny standard requests, it was the most likely to deny those that were expedited, at a rate of 13%.

On average, 12% of standard prior authorization requests for patient care were denied by Medicare Advantage insurers, as were 10% of all requests that were expedited.

When it came to Medicaid managed plans, Independence Health Group was found to have denied standard requests 23% of the time, significantly more than the 14% average. Looking at expedited requests, on average those were rejected 12% of the time, but CareSource has a denial rate of almost double that, 21%.

For private insurance sold through the federal ACA marketplace, prior authorization requests were denied 18% of the time for standard and at a rate of 16% for expedited requests. The worst offender was Centene in both instances, denying requests for care coverage 25% of the time for standard requests and 23% for expedited.

“Federal efforts to increase transparency into prior authorization practices in commercial coverage have so far been limited to ACA plans on the federally facilitated marketplace. There is no publicly available prior authorization data for self-funded plans sponsored by private employers, which cover the majority of workers with employer-sponsored health insurance,” KFF wrote. “Some states have taken action to increase transparency into prior authorization practices, including by collecting more granular prior authorization data from state-regulated insurers than the 2024 federal regulation requires and using the data to inform future actions aimed at curbing certain insurer practices.”

Appeals and response times

KFF added that prior authorization decisions are “rarely appealed,” but when they are, the success depends on the coverage type: 67% of denials were overturned for Medicare Advantage plans, followed by 47% for Medicaid managed care and 43% for ACA plans.

Response times also varied. The median time it took an insurer to respond to a prior authorization request was about one day across the board for all plan types. That didn’t change much if a request was expedited, except that Medicare Advantage plans were found to respond faster, at approximately half a day.