Key Takeaways:
Medicare Advantage plans denied 12% of standard prior authorization requests in 2025, with denial rates ranging from 5% at Elevance to 17% at UnitedHealth Group, a KFF analysis of insurer data found.
"Health insurers use prior authorization to reduce the use of low-value or unnecessary care, and in the complex and fragmented U.S. health care system is one of the primary tools used to restrain costs," the KFF study's authors wrote. "Nevertheless, this practice may result in delays or denials in receiving necessary care, as well as administrative burdens for patients and providers."
KFF, an independent health policy organization based in San Francisco, analyzed publicly available prior authorization metrics for calendar year 2025 from 14 insurers. The data covered 25 million Medicare Advantage enrollees, 35 million Medicaid managed care organization enrollees and nearly 11 million federally facilitated ACA Marketplace enrollees. Among the six largest Medicare Advantage insurers, expedited-request denial rates varied from 3% at Elevance to 13% at Centene.
The spread carries direct consequences for retirees entering the Medicare Annual Enrollment Period, which runs Oct. 15 through Dec. 7 for 2027 coverage. Prior authorization denials are rarely appealed, but appeals often succeed: 67% of appealed standard-request denials were overturned in Medicare Advantage, compared with 47% in Medicaid managed care and 43% in the federally facilitated ACA Marketplace.
The denial burden falls hardest on the most expensive services. A June report from the HHS Office of Inspector General found that Medicare Advantage insurers denied 65% of prior authorization requests for long-term hospital stays and 54% of inpatient rehabilitation facility stay requests. UnitedHealth, Humana and CVS each denied more than 70% of long-term care requests and more than 50% of inpatient rehab facility requests, according to OIG data.
Because the KFF metrics were aggregated across medical items and services, the data do not show which service categories, including home health, had the highest denial rates. Medicare Advantage plans typically authorize initial home health visits and require additional approvals before patients obtain services, a process that can take more than a week and cause patients to forgo or pay out of pocket for home-based care.
A denial letter should outline the reason for the denial, the policy or guideline used and how to appeal. Most plans allow at least one internal appeal, with urgent care appeals decided within 72 hours, pre-service claims within 30 days and post-service claims within 60 days. Supporting documentation from a doctor, including medical records and a letter of medical necessity, can strengthen an appeal.
The administrative load is prompting federal action. Dr. Mehmet Oz, administrator of the Centers for Medicare & Medicaid Services, has promoted digitizing prior authorization, citing estimates that the process costs providers nearly $34,000 and 700 administrative hours per provider annually. In May, he set a Jan. 1, 2027, deadline for CMS-regulated payers to integrate electronic prior authorization interfaces.
Retirees comparing plans for 2027 should weigh each insurer's denial record before the enrollment window closes. The Medicare Advantage Open Enrollment Period, Jan. 1 through Mar. 31, allows one additional switch to another Medicare Advantage plan or a return to Original Medicare.
This article is for informational purposes only and does not constitute investment advice.
