What Is Prior Authorization? How to Fight Denials

Your doctor's office called to say your insurer requires prior authorization before they'll cover your MRI, your specialist visit, or the medication your doctor just prescribed. Or worse — you already got the approval, scheduled the procedure, and now the insurer is refusing to pay. Either way, you're stuck in a system that can feel deliberately opaque. This article explains exactly what prior authorization is, why it causes delays, what your legal rights are when it's denied, and the specific steps you can take to fight back.

What Is Prior Authorization?

Prior authorization (sometimes called "prior auth," "pre-authorization," or "pre-certification") is a requirement that your health insurer approve a specific service, medication, or procedure before you receive it. Without that approval, your insurer may refuse to pay — even if your doctor has already determined the care is medically necessary.

Insurers use prior authorization to verify that a requested service meets their definition of "medical necessity" — a standard they set themselves, which may differ from your doctor's clinical judgment. That gap is the source of most prior auth conflicts.

What Typically Requires Prior Authorization

Not every service requires prior auth, but the following commonly do:

• Imaging studies — MRI, CT scans, PET scans
• Specialist visits (on some plans)
• Surgical procedures, including outpatient surgery
• Inpatient hospital admissions
• Durable medical equipment (DME) — wheelchairs, CPAP machines, insulin pumps
• Certain prescription medications, particularly brand-name drugs, specialty drugs, and biologics

An important distinction: Prior authorization for prescription drugs is typically managed by a pharmacy benefit manager (PBM) — a separate company your insurer contracts with to handle drug coverage. The appeal process for a denied drug prior auth may go through the PBM rather than your insurer directly. Ask your pharmacy or insurer which entity handles the denial so you appeal to the right place.

Why Prior Authorization Delays and Blocks Care

The administrative burden of prior authorization falls almost entirely on physician offices — not insurers. A single prior auth request can require hours of staff time: completing forms, gathering clinical records, following up by phone, and waiting for a decision that may never come or may arrive too late to matter. According to the Centers for Medicare & Medicaid Services (CMS), prior authorization is one of the leading sources of administrative burden in the U.S. healthcare system. That overhead is baked into the cost of care — and it comes at the direct expense of time physicians could spend with patients.

For patients, the consequences are concrete. A prior auth delay for an MRI can postpone a cancer diagnosis. A denied authorization for a specialty medication can interrupt treatment that took months to establish. These are not hypothetical outcomes — they are documented, recurring harms.

Timeline Rules: How Long Can Your Insurer Take?

Your insurer cannot take indefinitely long to respond. Under rules implementing the Affordable Care Act (ACA), insurers must meet these minimum timelines:

• Standard (non-urgent) prior auth decisions: within 15 calendar days of receiving a complete request (some plans have up to 30 days)
• Urgent/expedited prior auth decisions: within 72 hours when a delay could seriously jeopardize your health

If you are covered by a Medicare Advantage plan, faster rules apply under the Improving Seniors' Timely Access to Care Act, signed into law in 2022. Medicare Advantage plans are now required to make expedited decisions within 72 hours and standard decisions within 7 calendar days, and CMS has increased oversight of plans that overuse prior auth denials.

If your insurer misses these deadlines, that violation itself is grounds for a complaint to your state insurance commissioner. Document the dates of every request and response.

Prior Authorization Is Not a Payment Guarantee

This is one of the most important — and least understood — facts about prior authorization: receiving prior auth approval does not guarantee your claim will be paid. Insurers can and do retroactively deny claims after initially approving them, citing reasons such as coding errors, benefit limits, or a post-service determination that the care wasn't medically necessary after all.

Protect yourself by keeping a written record of every prior auth interaction:

• The authorization reference number
• The date the approval was granted
• The name of the representative who approved it (for phone approvals)
• The specific service, procedure code, and dates of service covered

If your insurer retroactively denies a claim after granting prior auth, appeal immediately. Your appeal should state clearly that you received explicit written approval, that you and your provider relied on that approval to proceed, and that reversing it after the fact is both contractually and legally problematic. The legal concepts here — detrimental reliance and promissory estoppel — support the argument that an insurer cannot induce you to proceed with care and then refuse to pay for it. If this happens to you and the insurer refuses to reverse the denial, consulting an attorney who handles insurance disputes is worth considering. We don't provide legal advice, but an attorney can evaluate whether you have a bad-faith claim under your state's laws.

What to Do When Prior Authorization Is Denied

A denial is not the end of the road. Most denials are reversed on appeal — particularly when a physician is actively involved. Here is the step-by-step process, drawn from guidance at Healthcare.gov.

Step 1: Get the Denial in Writing

Request a written explanation of the denial that includes the specific reason and the exact medical necessity criteria your insurer used to evaluate the request. You are legally entitled to this. Without knowing the insurer's stated objection, you cannot effectively challenge it.

Step 2: Request a Peer-to-Peer Review

Ask your doctor's office to request a peer-to-peer review — a direct phone conversation between your physician and the insurer's medical reviewer (usually another physician). This step happens before or during an internal appeal and is often the fastest path to a reversal. In many cases, the insurer's reviewer simply hasn't seen the full clinical picture. Ask your doctor's office specifically: "Can you request a peer-to-peer with the insurer on my behalf?"

Step 3: Have Your Doctor Submit a Letter of Medical Necessity

Your doctor should write a letter that directly addresses the insurer's stated reason for denial — not a generic letter, but one that engages the specific criteria the insurer used. If the insurer said the requested MRI wasn't medically necessary because conservative treatment hadn't been tried, the letter should document the conservative treatments already attempted and why they failed or are inappropriate.

Step 4: File an Internal Appeal

File a formal internal appeal with your insurer. Under ACA rules, insurers must decide internal appeals within these timeframes:

• Urgent/expedited appeals (when delay would seriously harm your health): within 72 hours
• Standard appeals: within 30–60 days, depending on your plan type

Be realistic: the standard internal appeal process can take several weeks. If your situation is urgent, explicitly request an expedited review in writing and state why a delay would jeopardize your health.

Step 5: File for External Independent Review

If your internal appeal fails, you have the right to an external review by an independent organization that has no financial relationship with your insurer. Under federal law, the external reviewer's decision is typically binding on your insurer — they cannot simply ignore it. Learn more about your external review rights at CMS's external appeals page. For a broader guide to this process, see our article on how to appeal a denied insurance claim.

Step 6: File a Complaint With Your State Insurance Commissioner

At any point in this process — especially if the insurer is missing legal deadlines or the denial appears arbitrary — file a complaint with your state's insurance commissioner. Regulators track complaint patterns and can investigate. This step costs you nothing and creates an official record.

A Concrete Example

A patient is referred by her primary care physician for a lumbar spine MRI after six weeks of back pain. Her insurer denies the prior auth, stating she hasn't completed a required course of physical therapy. Her doctor submits a letter noting that the patient has a history of spinal stenosis and that physical therapy is contraindicated given her imaging history. The doctor requests a peer-to-peer review. On the call, the insurer's reviewer reverses the denial. The MRI is approved. Total elapsed time: 11 days. Cost to the patient if she had paid out of pocket without insurance: approximately $1,200–$2,500 depending on facility. The peer-to-peer step alone saved weeks of additional appeals — and that cost.

State-Level Protections Worth Knowing

Federal law sets a floor, but many states have passed laws that go further. California's AB 2961 restricts prior authorization requirements for certain services. Texas has enacted laws mandating faster decisions and limiting step therapy (where insurers require you to try cheaper drugs before covering the one your doctor prescribed). Check your state insurance commissioner's website for laws specific to your state, as these protections can significantly strengthen your appeal. For more on how hospital and insurance billing intersects with these issues, see our guide to hospital billing explained.

What to Do Right Now

If you are facing a prior authorization denial today, start here:

1. Call your insurer and request the denial in writing with specific criteria.
2. Ask your doctor's office to request a peer-to-peer review immediately.
3. Tell your doctor's office you need a letter of medical necessity that directly responds to the insurer's stated objection.
4. File your internal appeal as soon as you have the written denial — clock the deadline.
5. If your health is at risk, request expedited review in writing.
6. If the internal appeal fails, file for external review.
7. At any point, file a complaint with your state insurance commissioner if deadlines aren't being met.

The prior authorization system is burdensome by design and can feel like it's built to outlast your patience. Most denials are reversed when patients and physicians push back systematically. Document everything, meet every deadline, and use every level of appeal available to you.

Sources: CMS — Prior Authorization and Burden Reduction, Healthcare.gov — How to Appeal an Insurance Company Decision, CMS — External Review Rights