Prior authorization is the process by which your health insurer requires advance approval before you can receive a specific medication, procedure, specialist visit, or post-acute care placement and have it covered. It is the single most common source of health insurance complaints in the United States — and in 2026, it is the subject of congressional hearings, class action lawsuits, and sweeping new federal rules precisely because it is being applied at a scale and through algorithms that frequently produce clinically indefensible decisions.
This guide explains what prior authorization is, why it exists, how it works, and most importantly: your complete step-by-step process for getting approved the first time and for winning an appeal when you are denied.
Studies consistently show that 80% or more of prior authorization appeals are overturned when properly filed. The vast majority of people who receive a denial never file an appeal. Filing one — with the right documentation — is the single most effective action you can take.
What Prior Authorization Actually Is — And Why Insurers Use It
Prior authorization exists because health insurance companies need a mechanism to review whether a requested service meets their coverage criteria before paying for it. From the insurer’s perspective, this serves three purposes: confirming medical necessity, ensuring lower-cost alternatives have been considered, and preventing fraud. From the patient’s perspective, it frequently feels like an obstacle course designed to make them give up.
The services most commonly requiring prior authorization include: certain prescription medications (particularly specialty drugs, GLP-1 medications, and newer biologics), elective surgeries, advanced imaging (MRI, CT, PET scans), physical therapy beyond a set number of sessions, mental health and substance abuse treatment, home health and skilled nursing facility placements, specialist consultations in some plans, and out-of-network services.
The mechanism has expanded significantly in the past decade. A 2023 American Medical Association survey found that 94% of physicians reported prior authorization causing delays in care, and 33% reported it causing a serious adverse event for a patient. In Medicare Advantage specifically, the Senate Permanent Subcommittee on Investigations documented in 2024 that major insurers deployed AI algorithms — specifically UnitedHealthcare’s nH Predict tool — to process requests at industrial scale, generating denial recommendations that clinical reviewers then stamped without independent review.
How the Prior Authorization Process Actually Works
When your doctor prescribes a medication or recommends a procedure, the prior authorization process begins in one of two ways: your pharmacy submits it to the insurer automatically (for medications), or your doctor’s office submits a PA request on your behalf (for procedures and specialist visits). In both cases, the request goes to the insurer’s utilisation management department, where it is reviewed — often by an algorithm first, then by a clinical reviewer if flagged.
The insurer will look for: whether the service is listed on their covered services schedule, whether you meet the clinical criteria in their medical policy for that service, whether a step therapy requirement applies (meaning you must try a cheaper alternative first), and whether the documentation submitted is complete.
The most common reason requests fail is incomplete documentation at submission. If your doctor’s office sends the request without attaching the clinical notes that establish medical necessity, the insurer will deny or pend it. This is not a judgment about your condition — it is an administrative failure that can be corrected.
How to Get Approved the First Time
The best prior authorization outcome is approval before care is needed. Several steps improve the likelihood of first-pass approval:
- Ask your doctor’s office to confirm PA is required before scheduling. Call your insurer’s member services number with the specific CPT code for the procedure and ask directly whether prior authorisation is required for your plan. Do not rely on the provider’s office to always know — PA requirements vary by plan and change frequently.
- Ask your doctor to submit a complete clinical package. The PA request should include: the specific diagnosis codes (ICD-10), the treatment codes (CPT), clinical notes documenting the diagnosis and treatment rationale, relevant test results or imaging, and documentation of any previous treatments attempted. A bare PA request with just the treatment code is frequently denied.
- Check the insurer’s clinical policy before submission. Most insurers publish their medical necessity criteria on their website. If you can find the policy for your specific service, your doctor’s submission should explicitly address and meet each listed criterion.
- For medications: check the step therapy requirements. If the drug requires step therapy, the PA request must document that the required prior medications were tried and failed or were contraindicated. Submitting this evidence upfront prevents the most common medication denial reason.
When You Are Denied: The Complete Appeal Process
Under the 2026 CMS Interoperability and Prior Authorization Final Rule, insurers must now provide a specific clinical reason for every prior authorization denial. This is a meaningful change from previous practice, where denials often cited generic categories. The specific reason is your appeal’s foundation.
Standard PA requests: insurer must decide within 7 calendar days. Urgent PA requests (where delay could harm health): 72 hours. Your internal appeal: most plans allow 180 days to file (Medicare Advantage: 60 days). External review: typically 4 months after internal appeal exhaustion.
Step 1: Request the Peer-to-Peer Review First
Before filing a formal appeal, ask your doctor to request a peer-to-peer review. This is a direct call between your treating physician and the insurer’s medical reviewer — bypassing the algorithm entirely. Your physician explains your specific clinical situation to another physician. Approval rates following peer-to-peer reviews are substantially higher than for formal appeals, and it does not use up any appeal rights. Your doctor calls the insurer’s provider line and requests it — it should be completed within 72 hours for urgent cases.
Step 2: File the Internal Appeal With a Physician Letter
If the peer-to-peer does not resolve it, file a formal internal appeal within the required window. The appeal letter should: quote the specific clinical denial reason verbatim, explain why that reason does not apply to your specific situation, reference your physician’s supporting clinical notes, cite any relevant peer-reviewed clinical guidelines or your insurer’s own medical policy, and close by requesting reversal and approval.
The physician’s letter of medical necessity — signed by your treating doctor and specifically addressing the denial reason — is the most powerful document in an appeal. A letter that simply says “this treatment is medically necessary” is weak. A letter that says “the denial cited criterion X; this patient meets that criterion because of Y and Z as documented in the attached clinical notes dated [date]” is strong.
Step 3: External Independent Review
If the internal appeal fails, request external review by an Independent Review Organisation (IRO). The IRO reviewer has no financial relationship with your insurer. They review the clinical evidence independently. Under federal law, their decision is binding on the insurer. This is the level where the majority of overturned denials occur. Submit everything: clinical notes, physician letter, peer-reviewed medical literature, relevant clinical guidelines, and documentation of any harm or urgency.
When to Request Expedited Review
If your situation is urgent — ongoing cancer treatment, a hospital discharge dispute, acute specialist care — you have the right to expedited review at every level. Your physician certifies that a delay in the standard review timeline could adversely affect your condition. The insurer must then respond within 72 hours. Do not accept a standard timeline for urgent medical situations.
