What Is Prior Authorization (and Why Does Your Insurance Require It)?

By the PolicyZen Team · Updated March 2026 · 9 min read

Your doctor says you need an MRI. Your insurance says you need prior authorization first. What does that mean, why does it exist, and what happens if you skip it?

Prior authorization (also called pre-authorization, pre-approval, or pre-cert) is a requirement by your insurance company to review and approve certain medical treatments, medications, or procedures before they are performed. Without approval, your insurer may not cover the cost.

Why Do Insurance Companies Require Prior Authorization?

There are two real reasons — one legitimate, one frustrating.

The legitimate reason: Medical necessity review

Insurers use prior auth to confirm that requested treatments are medically necessary and supported by clinical evidence. Not every treatment a doctor orders is the most appropriate or cost-effective option for a given condition. Prior auth is supposed to catch cases where a less expensive, equally effective treatment should be tried first.

The frustrating reason: Cost control

Prior auth also serves as a friction mechanism that reduces utilization. Studies show that some requests are abandoned when prior auth is required — sometimes because they weren't truly necessary, but sometimes because patients and doctors simply gave up on navigating the process. Insurers benefit financially from approvals that never come through because providers stop trying.

What Commonly Requires Prior Authorization?

• Brand-name or specialty medications (especially biologics and newer drugs)
• Advanced imaging (MRI, PET scans, CT scans)
• Elective surgeries and procedures
• Inpatient hospital admissions (for non-emergency care)
• Physical, occupational, or speech therapy (often requires ongoing auth)
• Durable medical equipment (wheelchairs, CPAP machines)
• Mental health and substance abuse treatment
• Out-of-network specialist referrals
• Home health care services

How Does the Prior Authorization Process Work?

1. Your doctor's office submits a request. This is typically done by your provider — not you. The office submits clinical documentation supporting the medical necessity of the treatment.
2. The insurer reviews the request. An insurance company reviewer (often a nurse or physician) evaluates whether the treatment meets the plan's coverage criteria. For routine requests, this may be automated.
3. Decision: Approved, denied, or pending. Approvals can come in hours or take weeks. Urgent/expedited reviews should come within 24–72 hours by law. Standard reviews can take up to 15 days.
4. If denied, you have the right to appeal. Always appeal a denial. Initial denial rates are significant, and appeals succeed more often than most patients realize.

What Happens If You Don't Get Prior Authorization?

If you receive a service that required prior auth and didn't get it:

• The insurer may deny the claim entirely
• You may receive a bill for the full amount (potentially thousands of dollars)
• You can appeal and argue the service was medically necessary — sometimes successfully
• If there was a genuine medical emergency, emergency care typically doesn't require prior auth

How to Appeal a Prior Authorization Denial

Approximately 30–50% of prior auth appeals succeed when pursued properly. Here's what to do:

1. Get the denial in writing. Request a detailed written explanation stating the specific reason for denial and the criteria used to evaluate it.
2. Have your doctor write a letter of medical necessity. This should directly address the insurer's stated reason for denial with clinical evidence and notes from your medical record.
3. Request a peer-to-peer review. Your doctor can request to speak directly with the insurer's medical reviewer. This call often changes outcomes — physician-to-physician communication carries more weight than written requests.
4. File a formal appeal. Insurers must provide an internal appeal process. Submit your appeal with supporting documentation within the timeframe stated in your denial letter.
5. Request an external review. If your internal appeal is denied, you have the right to an independent external review by a third-party organization. For urgent medical situations, external review decisions often come within 72 hours.

Prior Authorization in Emergencies

Emergency services cannot require prior authorization. If you are experiencing a medical emergency and receive care at the nearest emergency facility (even out-of-network), your insurer must cover it at in-network cost-sharing levels under federal law. You cannot be penalized for not calling your insurer before going to the ER in a true emergency.

Frequently Asked Questions