If you are enrolled in a Medicare Advantage plan — and roughly 33 million Americans are as of 2024, according to CMS.gov data — you may have already run into a frustrating wall: your doctor recommends a treatment, a procedure, or a stay in a rehabilitation facility, and the insurance company says no. What many beneficiaries do not realize is that the entity making that initial denial may not be a doctor, a nurse, or even a human being. It may be an algorithm.
Medicare Advantage plans, which are private insurance alternatives to Original Medicare sold by companies like UnitedHealthcare, Humana, Aetna, and CVS Health's Aetna subsidiary, are required by law to cover everything that Original Medicare covers. But unlike Original Medicare, these plans use a process called prior authorization — a requirement that your doctor get the insurer's permission before you receive certain treatments, procedures, or post-acute care like skilled nursing or home health services. That permission process is increasingly being handled, at least in part, by artificial intelligence tools that scan claims data and flag requests for denial based on statistical patterns rather than your individual medical situation.
The concern is not hypothetical. A Senate Permanent Subcommittee on Investigations report released in 2024 examined three of the largest Medicare Advantage insurers — UnitedHealthcare, Humana, and CVS Health — and found that all three used AI or algorithmic tools in their prior authorization processes. The report found that UnitedHealthcare used a tool called nH Predict, developed by NaviHealth, to determine the appropriate length of post-acute care stays for Medicare Advantage patients. Internal data reviewed by investigators showed that the tool had an error rate — meaning it predicted patients would be ready for discharge before their physicians believed they were — that resulted in thousands of premature coverage denials. Humana and CVS Health used similar tools. In each case, the algorithms were making or heavily influencing coverage decisions that affected real patients recovering from strokes, hip replacements, and serious illnesses.
What makes this particularly troubling for beneficiaries is the power imbalance involved. When you receive a denial letter, it typically arrives in dense insurance language, cites a clinical policy bulletin you have never seen, and gives you a short window to respond. Many seniors, especially those who are already ill or recovering from a procedure, simply accept the denial and either pay out of pocket or go without care. The insurance industry is counting on that. According to KFF analysis of CMS data, Medicare Advantage plans denied approximately 3.4 million prior authorization requests in 2021 alone — and only a small fraction of those denials were ever appealed. Of the appeals that were filed, however, beneficiaries won a significant portion, which suggests that many of the original denials were not clinically justified.
Data Snapshot: According to CMS.gov data from the 2024 Medicare Advantage and Part D Star Ratings release, there were 861 Medicare Advantage organizations offering 7,392 plan options nationwide in 2024. That proliferation of plans has intensified competition among insurers to control costs — and prior authorization denials are one of the primary tools used to do exactly that. CMS also reported that the average Medicare Advantage plan premium in 2024 was approximately $18.50 per month, a figure that looks attractive on the surface but does not account for the cost-sharing, network restrictions, and authorization hurdles that can make accessing care far more expensive in practice.
So what can you actually do if your Medicare Advantage plan denies a claim or a prior authorization request? The first and most important step is to request a written explanation of the denial immediately. Under federal rules, your plan must tell you in writing why the request was denied and what clinical criteria were used to make that decision. Ask your doctor's office to help you obtain the specific clinical policy bulletin the insurer cited — these documents are often publicly available on the insurer's website, and comparing the insurer's criteria to your actual medical records can reveal whether the denial was applied correctly.
Next, file an appeal — and do it quickly. For Medicare Advantage, the appeals process has five levels. Level 1 is an internal appeal with your plan, which must be decided within 72 hours for urgent or expedited requests and 30 days for standard requests. If that appeal is denied, Level 2 takes your case to a Qualified Independent Contractor (QIC), which is an outside organization contracted by CMS to review disputes. Level 3 involves an Administrative Law Judge hearing, Level 4 goes to the Medicare Appeals Council, and Level 5 allows you to file in federal district court. Most beneficiaries who win their appeals do so at Levels 1 or 2, so do not be discouraged by the initial denial — the system is designed to be navigated.
Your doctor is your most powerful ally in this process. Ask your physician to write a detailed letter of medical necessity that directly addresses the insurer's stated reason for denial. If the denial cited a clinical guideline, the letter should explain why your specific case falls outside the standard algorithm — your age, comorbidities, functional limitations, and prior treatment history all matter. Physicians who are experienced with Medicare Advantage appeals know that specificity wins. A generic letter saying the treatment is 'medically necessary' is far less effective than one that says 'this patient has a documented history of falls, a recent hip fracture, and a comorbid diagnosis of Parkinson's disease that makes the standard discharge timeline clinically inappropriate.'
If you are facing a denial for post-acute care — meaning a skilled nursing facility stay, home health services, or inpatient rehabilitation — you have an additional protection that many beneficiaries do not know about. You are entitled to a fast appeal, also called an expedited appeal, if you believe your discharge from a hospital or facility is premature. You must contact your Beneficiary and Family Centered Care Quality Improvement Organization (BFCC-QIO) — a CMS-contracted organization that handles these urgent reviews — before you leave the facility. The BFCC-QIO must make a decision within one day of receiving your medical records. During the review period, the facility cannot discharge you and cannot bill you for the disputed days. You can find your regional BFCC-QIO by calling 1-800-MEDICARE or visiting Medicare.gov.
There is also a broader policy context worth understanding. CMS has been aware of the AI denial problem and has taken some steps to address it. In 2024, CMS issued updated guidance clarifying that Medicare Advantage plans must make coverage decisions based on individual patient circumstances and cannot use algorithmic tools as a substitute for individualized clinical review. The agency also finalized rules requiring Medicare Advantage plans to make prior authorization decisions faster and to improve the transparency of their denial criteria. However, enforcement remains a challenge, and the rules do not prohibit the use of AI tools entirely — they simply require that a qualified clinician review the algorithm's output before a denial is issued. Whether that review is meaningful or perfunctory varies significantly by insurer.
For beneficiaries who are shopping for a Medicare Advantage plan during the Annual Enrollment Period — which runs from October 15 through December 7 each year — prior authorization burden is now a legitimate factor to weigh alongside premiums and network coverage. CMS publishes prior authorization data by plan, and you can use the Medicare Plan Finder tool at Medicare.gov to compare plans. Look for plans with higher Star Ratings, particularly in the 'Getting Needed Care' and 'Getting Appointments and Care Quickly' categories, as these ratings reflect member experience with access to care. A plan with a $0 premium but a pattern of aggressive prior authorization denials may cost you far more in delayed or denied care than a plan with a modest monthly premium and a more permissive authorization policy.
If you are currently enrolled in Medicare Advantage and feel that AI-driven denials are systematically affecting your access to care, you can file a complaint with CMS directly through Medicare.gov or by calling 1-800-MEDICARE. You can also contact your State Health Insurance Assistance Program (SHIP), which provides free, unbiased counseling to Medicare beneficiaries. SHIP counselors can help you understand your rights, navigate the appeals process, and identify whether switching plans during the next enrollment window might better serve your health needs. The Open Enrollment Period, which runs from January 1 through March 31 each year, allows Medicare Advantage enrollees to switch plans or return to Original Medicare once without penalty — a window worth considering if your current plan has repeatedly denied necessary care.
Finally, it is worth remembering that Original Medicare — Parts A and B — does not use prior authorization for most services. If you are consistently running into authorization barriers with your Medicare Advantage plan, returning to Original Medicare paired with a Medigap supplemental policy may give you significantly more freedom to access care without algorithmic gatekeeping. Medigap Plan G, for example, covers nearly all out-of-pocket costs under Original Medicare after the Part B deductible, which was $240 in 2024. The tradeoff is a higher monthly premium — average Medigap Plan G premiums nationally range from roughly $100 to $200 per month depending on your age, gender, and location — but for beneficiaries with complex medical needs, that predictability and freedom of access can be worth every dollar.