Patients who challenge a health insurer's refusal to cover care often win, yet few ever try, according to a Bloomberg analysis published September 14. The report found that about half of prior authorization denials are reversed when appealed, and as many as nine in 10 in some plans, and it questioned why insurers deny so many doctor-ordered services in the first place.
The findings echo newly public insurer data. A KFF analysis of insurer prior authorization data, released in August, looked at 2025 figures and found that 67% of appealed denials were overturned in Medicare Advantage, 47% in Medicaid managed care, and 43% in Affordable Care Act (ACA) marketplace plans sold through HealthCare.gov.
For households, the gap between how often appeals succeed and how rarely they are filed can mean delayed scans, postponed surgeries, or care that goes unfunded. A denial letter is often the start of a process, not the final answer.
Insurer Data Show Wide Gaps in Appeal Outcomes
The KFF figures come from reports that a 2024 federal rule required insurers to post online by March 31, 2026. Researchers collected data from 14 insurers covering about 71 million people. On average, insurers denied 12% of standard prior authorization requests in Medicare Advantage, 14% in Medicaid managed care, and 18% in the ACA marketplace.
Denial rates differed widely by company. Among the marketplace insurers, GuideWell, which includes Blue Cross and Blue Shield of Florida, denied 3% of standard requests, while Centene's plans denied 25%. For shoppers in HealthCare.gov states such as Texas and Florida, the company behind a plan can shape the odds of hearing no in the first place.
Appeal results also varied sharply. In Medicare Advantage, Centene overturned 93% of appealed denials, while Kaiser Permanente overturned 40%. Among Medicaid plans, UnitedHealth Group reversed 81%, and CVS reversed 22%. In marketplace plans, Health Care Service Corporation, whose plans in the analysis include Blue Cross and Blue Shield of Texas, reversed 16%, and Centene reversed 54%.
KFF researchers wrote that denials are rarely appealed, but "when they are, a considerable share are overturned." High reversal rates could mean the original request should have been approved, or that it lacked the documentation needed to justify the service, they said. Either way, the appeals process can be complicated and time-consuming for patients and doctors.
The data have important limits. Insurers report percentages rather than counts, do not break results down by service, and can report 0% without saying whether any appeals were filed. The marketplace figures cover only the 28 states that used HealthCare.gov in 2025, so states that run their own exchanges, including California and New York, are not included. Bloomberg's full methodology is behind a paywall and could not be independently reviewed.
Internal Appeals and External Reviews Work Differently
An internal appeal asks the insurer to reconsider its own decision. An external review sends the dispute to an independent organization outside the company, and the insurer must accept that reviewer's decision, according to federal appeals guidance from CMS. Most plans must offer both steps, though some older, grandfathered plans may follow different rules.
Plan type shapes the path. In Medicare Advantage, a denial the plan upholds is automatically sent to an independent reviewer. Medicaid managed care and marketplace plans have no automatic external review of upheld denials, and federal inspectors have suggested that difference may help explain why Medicare Advantage plans reverse more denials on appeal.
Independent review can be decisive. A JAMA Internal Medicine study of about 51,000 completed external appeals in New York State found that nearly half were overturned, and the overturn rate rose from 38% in 2019 to 52.5% in 2025. For New Yorkers, that means a denial upheld by the insurer still has a meaningful chance of being reversed.
Many people never reach that stage. A Commonwealth Fund survey found that only about half of adults who experienced a denial appealed it, often because they were unsure of their rights, doubted it would help, or did not know whom to contact.
Building a Stronger Appeal Starts with the Denial Letter
The first step is getting the denial in writing with the specific reason, which plans covered by the 2024 federal prior authorization rule must now provide. Patients should ask the ordering clinician whether the office can request a peer-to-peer review with the plan's reviewer or resubmit the request with stronger records, which can quickly fix documentation problems. Patients can also ask the plan for the records and coverage criteria behind the decision, which federal claims rules generally require plans to provide free of charge.
Deadlines matter. For many private plans, patients have 180 days after a denial to file an internal appeal and as few as 60 days after a final denial to request external review, according to CMS. The exact deadlines appear on the denial notice, so households should note them right away. When a delay could seriously harm a patient's health, an expedited appeal must generally be decided within 72 hours. Keeping copies of every letter, along with call dates and representatives' names, makes a later external review stronger.
Those at greatest risk of harm include people awaiting cancer care, patients being discharged to rehabilitation or skilled nursing, and anyone who cannot afford to pay upfront while a dispute continues. Free help is available through state insurance departments, marketplace navigators, and, for Medicare enrollees, State Health Insurance Assistance Programs. No one should skip emergency care while a coverage question is pending.
More transparency is coming, though slowly. CMS issued an updated reporting template in July for the 2027 reporting period, and a pending proposed rule would require insurers to publish request counts and add prescription drug data. Electronic prior authorization requirements take effect January 1, 2027, and some states, including Massachusetts, have already eliminated prior authorization for certain routine in-network services. Patients in self-funded employer plans, however, still have no comparable public data.
Key Questions Answered
How often are appealed insurance denials reversed? KFF found reversal rates of 67% in Medicare Advantage, 47% in Medicaid managed care, and 43% in HealthCare.gov marketplace plans for 2025 prior authorization denials. Bloomberg's analysis put the figure at about half.
What is the difference between an internal appeal and an external review? An internal appeal asks the insurer to reconsider. An external review goes to an independent organization, and the insurer must accept its decision.
Does every insurer reverse denials at the same rate? No. Among the large insurers KFF examined, reversal rates ranged from 16% at one marketplace insurer to 93% at one Medicare Advantage insurer.
How long do I have to appeal? Deadlines vary by plan and are listed on the denial notice. Many private plans allow 180 days for an internal appeal, and urgent cases can qualify for a decision within 72 hours.
Why are so many denials overturned? KFF says the original request may have deserved approval, or it may have lacked needed documentation. The data do not show which explanation applies to specific cases.
Where can I get free help with an appeal? State insurance departments, marketplace navigators, and State Health Insurance Assistance Programs for Medicare enrollees offer free guidance.
