One of the central trade-offs between Original Medicare and a Medicare Advantage plan is who decides, and how quickly, that a given treatment will be paid for. Medicare Advantage plans manage costs in part by requiring approval before certain services are delivered, a process known as prior authorization. That approval is not guaranteed, and federal reviewers have found that some plans deny requests for care that traditional Medicare would have paid for without question.
How prior authorization works inside Medicare Advantage
Prior authorization is nearly universal in the program. A KFF analysis of plan data found that almost every Medicare Advantage enrollee is in a plan that requires prior approval for at least some services, and that insurers collectively make tens of millions of these determinations each year. The requirement tends to concentrate on higher-cost care, including inpatient hospital stays, skilled nursing facility stays, and certain drugs and procedures. The scale of the practice is documented in KFF’s review of prior authorization determinations.
In practice this means a doctor’s judgment that a patient needs a service is not the final word. The plan can require paperwork, apply its own clinical criteria, and delay or refuse payment until those conditions are met.
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Denials for care Original Medicare would have paid
The most pointed finding came from federal auditors. An investigation by the Department of Health and Human Services Office of Inspector General examined a sample of prior authorization denials from the largest Medicare Advantage plans and found that a meaningful share, about 13 percent, were for services that met Medicare’s coverage rules. In other words, those beneficiaries would have received the care under Original Medicare, but were denied under their Medicare Advantage plan. The auditors estimated the pattern translated into tens of thousands of improper denials in a single year across major insurers.
Denials of that kind matter most when they involve time-sensitive care, such as a transfer to a rehabilitation facility after a hospital stay. A delay in approval can push a patient home sooner than a doctor recommends or force a family to pay out of pocket while an appeal grinds on.
Why traditional Medicare rarely says no in advance
The contrast with Original Medicare is stark. Traditional Medicare applies prior authorization to only a limited set of services, so for most care a provider bills after treatment and Medicare pays according to its coverage rules. Medicare Advantage plans, by design, insert an approval step in front of a much wider range of services. That structure is what allows the plans to control spending and offer extra benefits, but it is also what creates the possibility of a denial that Original Medicare would never have generated.
This is not a claim that Medicare Advantage is uniformly worse. The plans often cost less up front and add benefits that traditional Medicare lacks. The point is that the coverage comes with a gatekeeping process, and that process occasionally blocks legitimate care.
Appeals frequently succeed, yet few beneficiaries file them
The data on appeals reveals a quiet inefficiency. When Medicare Advantage enrollees challenge a denied prior authorization, a large majority of those appeals are overturned in the patient’s favor, according to KFF’s tracking. Yet only a small fraction of denials are ever appealed. That gap suggests many beneficiaries accept a denial that would have been reversed had they pushed back.
Every Medicare Advantage plan is required to provide an appeals process, and Medicare’s guidance on how to file an appeal lays out the steps and deadlines. A denial letter is a starting point, not a verdict. For a beneficiary weighing traditional Medicare against a Medicare Advantage plan, the prior authorization system is a real part of the calculation, and understanding that a plan can refuse care Original Medicare would have covered is what turns a surprise denial into a fight worth having.
This article was produced with AI assistance and reviewed by The Financial Wire editorial team.
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Warren Cohen is a finance writer based in Phoenix, Arizona, covering personal finance topics including credit, banking, and beginner investing. He earned his degree in business administration from Arizona State University and began his career working in consumer finance, where he gained direct experience with lending and credit systems. He now writes for personal finance websites and fintech platforms, focusing on clear, practical content that helps readers make informed financial decisions.
