Prior Authorization Denial Rates by Insurer: Medicare Advantage, Medicaid, and ACA Marketplace

Prior authorization has become one of the most closely watched parts of the U.S. health insurance system. New federal reporting data analyzed by KFF show that the experience can differ substantially depending on the insurer and the type of coverage.

Across the three major insurance markets examined, insurers denied at least 1 in 8 standard prior authorization requests in 2025. But the overall average hides much larger differences between individual insurers.

In Medicare Advantage, Medicaid managed care, and ACA Marketplace plans, standard denial rates averaged 12%, 14%, and 18%, respectively.

The bigger story is the gap between insurers.

Key Takeaway

Prior authorization denial rates vary sharply by insurer. KFF found rates ranging from 5% to 17% in Medicare Advantage, 2% to 23% in Medicaid managed care, and 3% to 25% in ACA Marketplace plans.

Prior Authorization Denial Rates Differ by Insurance Market

KFF analyzed 2025 prior authorization data from 14 insurers with the largest enrollment in each market.

The analysis found that ACA Marketplace plans had the highest average denial rate among the three markets, while Medicare Advantage had the lowest.

Medicare Advantage	12%
Medicaid managed care	14%
ACA Marketplace	18%

These figures cover standard prior authorization requests for medical items and services. They do not represent prescription-drug prior authorization.

The differences become even clearer when individual insurers are compared.

Insurers With the Highest Prior Authorization Denial Rates

KFF’s 2025 data show that prior authorization denial rates varied considerably among major insurers. The highest reported rate differed by insurance market, with UnitedHealth Group leading Medicare Advantage, Independence Health Group leading Medicaid managed care, and Centene recording the highest rate in the ACA Marketplace.

Medicare Advantage

Insurer	Standard denial rate
UnitedHealth Group	17%
Centene	15%
Kaiser Permanente	13%
CVS	8%
Humana	7%
Elevance	5%

Which Insurers Had the Highest Prior Authorization Denial Rates?

In Medicare Advantage, denial rates ranged from 5% for Elevance to 17% for UnitedHealth.

Medicaid managed care showed an even wider spread, from 2% for L.A. Care Plan to 23% for Independence Health Group.

In the ACA Marketplace, the range was 3% for GuideWell to 25% for Centene.

That means the highest reported denial rate in the ACA Marketplace was more than eight times the lowest rate in that market.

Fast Facts

• 12%—average Medicare Advantage denial rate
• 14%—average Medicaid managed care denial rate
• 18%—average ACA Marketplace denial rate
• 25%—highest reported ACA Marketplace denial rate
• 23%—highest reported Medicaid managed care denial rate
• 17%—highest reported Medicare Advantage denial rate

Many Prior Authorization Denials Are Never Appealed

The denial rate is only part of the story.

KFF found that relatively few denied requests were formally appealed. That means the initial denial often becomes the final decision, even though the appeals data show that many challenged decisions are later reversed.

Across the three markets, the share of denied requests that were appealed remained limited.

Among Medicare Advantage plans, previous KFF analysis of 2024 data found that only 11.5% of denied prior authorization requests were appealed.

But when those denials were appealed, 80.7% were partially or fully overturned.

That creates an important distinction: a denial does not necessarily mean the requested care ultimately remains denied.

Key Data Point

80.7% of appealed Medicare Advantage prior authorization denials were partially or fully overturned in 2024.

Why the New Data Matter for Patients

Until now, comparing prior authorization practices across insurers has been difficult because the underlying data were not publicly available in a consistent way.

That is beginning to change.

CMS required impacted insurers to publicly report prior authorization metrics for the previous calendar year under its 2024 Interoperability and Prior Authorization Final Rule. The first reporting cycle covered 2025 data, with insurers required to post specified metrics beginning in 2026.

The reporting includes approval and denial rates for standard prior authorization requests, as well as information about approvals after appeal.

That gives consumers, researchers, and policymakers a new way to see how insurers handle prior authorization.

But the Data Still Have Important Gaps

The new transparency does not provide a complete picture of prior authorization.

KFF noted that insurers generally report percentages rather than the total number of requests behind each metric. That makes it difficult to determine the absolute number of denials for individual insurers from the percentage alone.

The data also do not provide a consistent breakdown by specific type of medical service.

That matters because a denial rate across all covered medical services cannot tell a patient whether a particular procedure, treatment or type of care is more likely to require authorization or be denied.

KFF also found inconsistencies in how insurers reported the information, making some comparisons more difficult.

Medicare Advantage Shows Why Insurer-Level Differences Matter

Earlier KFF analysis of 2024 Medicare Advantage data provides additional context.

Medicare Advantage insurers made nearly 52.8 million prior authorization determinations in 2024. About 4.1 million, or 7.7%, were fully or partially denied.

But the insurer-level numbers varied considerably.

UnitedHealth had about 1.0 prior authorization request per enrollee and a 12.8% denial rate, while Humana had about 2.2 requests per enrollee and a 5.8% denial rate.

Across the large insurers studied, prior authorization use ranged from 0.6 requests per enrollee at Kaiser to 3.0 at Elevance and Centene.

The figures come from a different year and methodology than the new 2025 cross-market analysis, so they should not be treated as a direct year-to-year comparison. They do, however, reinforce the broader finding that prior authorization practices can differ substantially between insurers.

What CMS Is Changing About Prior Authorization

The federal government is also pushing insurers toward more transparent and electronic prior authorization processes.

Under CMS’s 2024 final rule, impacted payers must publicly report specified prior authorization metrics and implement electronic prior authorization capabilities. CMS says standard decisions must generally be provided within seven calendar days, while expedited decisions must be made within 72 hours.

CMS is also moving toward requiring specific reasons for denials through prior authorization APIs.

Separately, CMS proposed new rules in 2026 that would extend many prior authorization requirements to prescription drugs and introduce additional reporting requirements. Those changes remain proposed, rather than final.

What the Numbers Do—and Do Not—Tell Consumers

A higher denial rate does not automatically mean an insurer is improperly denying medically necessary care.

Insurers may have different prior authorization requirements, patient populations, provider networks, and service mixes. Those differences can affect the reported numbers.

At the same time, the high rate of successful appeals in Medicare Advantage shows why the initial denial rate alone is not enough to understand the full process.

The new data are therefore most useful as a starting point for comparing insurer practices, rather than as a simple ranking of which insurers approve or deny care.

The Bottom Line

The first broad look at publicly reported prior authorization data shows that there is no single denial rate across the U.S. insurance market.

KFF found average standard denial rates of 12% in Medicare Advantage, 14% in Medicaid managed care, and 18% in ACA Marketplace plans, with substantially wider differences among individual insurers.

The other important finding is what happens after a denial. Many denied requests are never appealed, but among Medicare Advantage requests that were appealed in 2024, more than four in five were partially or fully overturned.

As CMS’s new reporting requirements produce more insurer-level data, consumers and policymakers should get a clearer picture of not only how often insurers deny prior authorization requests, but also how often those decisions change after an appeal.

Frequently Asked Questions

What is prior authorization?

Prior authorization is a process in which a health insurer reviews and approves certain medical services, treatments, or items before they are provided or covered.

How often are prior authorization requests denied?

KFF found that average standard prior authorization denial rates in 2025 were 12% for Medicare Advantage, 14% for Medicaid managed care and 18% for ACA Marketplace plans.

Which insurance market had the highest denial rate?

The ACA Marketplace had the highest average denial rate at 18%. Among individual insurers analyzed by KFF, reported rates ranged from 3% to 25%.

Does a prior authorization denial mean the treatment is permanently denied?

No. A denial can generally be appealed, depending on the plan and circumstances. In Medicare Advantage, 80.7% of appealed prior authorization denials were partially or fully overturned in 2024.

How many prior authorization denials are appealed?

Only a relatively small share of denials are appealed. KFF’s 2024 Medicare Advantage analysis found that 11.5% of denied prior authorization requests were appealed.

Why do prior authorization denial rates vary between insurers?

Differences can reflect insurers’ authorization requirements, patient populations, provider networks, and the types of medical services being requested. A higher denial rate alone does not prove that an insurer is improperly denying medically necessary care.

Does the KFF data include prescription drug prior authorization?

The cross-market figures discussed in this article cover standard prior authorization requests for medical items and services, not prescription-drug prior authorization.

Can consumers use prior authorization data to compare insurers?

Yes, but the data should be treated as a starting point rather than a simple ranking. Denial rates do not provide the complete picture of an insurer’s prior authorization practices, and reporting limitations make some comparisons difficult.