PET Scan Denied by Insurance: How to Appeal

Key Takeaways

• A denial is not the end of the road. Roughly 1 in 5 health insurance claims is denied at first pass, and a substantial share are overturned when patients appeal — but most patients never file one.
• PET scan denials usually come down to one of three reasons: missing prior authorization, the request did not match the insurer's "medical necessity" criteria, or the documentation from the ordering doctor was incomplete.
• You typically have 60 to 180 days from the denial letter to file an internal appeal with a commercial plan, and 120 days for Medicare Part B. Mark the deadline the day the letter arrives.
• Two underused tools have high success rates: a peer-to-peer phone call between your ordering doctor and the insurance medical director, and an external review by an independent reviewer that the Affordable Care Act guarantees.
• You do not have to navigate this alone. Your ordering physician's office, the imaging center's billing team, and your state insurance department all have a stake in resolving denials and are often willing to help.

Why Insurance Plans Deny PET Scans

PET (positron emission tomography) scans are among the most expensive imaging studies in routine use, often billed at several thousand dollars. Insurers scrutinize them more aggressively than X-rays or basic CT. According to the American Cancer Society, the most common denial reasons fall into a handful of buckets.

The first bucket is prior authorization failures. Most commercial plans require approval before the scan is performed. If the imaging center performed the scan without the authorization on file, or the authorization was granted for a different CPT code than the one billed, the claim is denied automatically. This is administrative, not clinical, and is usually fixable.

The second bucket is medical necessity. Insurers maintain coverage policies (often based on American College of Radiology (ACR) Appropriateness Criteria or NCCN guidelines) that list which clinical indications justify a PET scan. A request for PET to evaluate a finding the insurer considers better suited for CT or MRI is typically denied.

The third bucket is documentation gaps. The ordering doctor must include a clear clinical indication, prior imaging results, biopsy findings if relevant, and the planned use of the PET result (e.g., staging, restaging, treatment response). Missing pieces lead to denial even when the scan is otherwise appropriate.

Step 1: Read the Denial Letter Carefully

Every denial letter must, by law, contain three pieces of information you need:

• The specific reason for denial — usually quoted from the insurer's coverage policy.
• The CPT code and date of service — confirm these match what was actually ordered.
• The deadline and address for appeals — this is the clock that starts ticking.

A 2026 PET scan billed under code 78815 (PET/CT skull-to-thigh) carries different coverage rules than 78816 (PET/CT whole body) or 78813 (PET only). A denial sometimes vanishes when the imaging center re-bills under the correct code.

Step 2: File the Internal Appeal

Every commercial plan, Medicare, and Medicaid is required to offer at least one level of internal appeal. The deadline is on the denial letter — typically:

• Commercial / employer plans: 60 to 180 days from the denial letter.
• Medicare Part B: 120 days to file a redetermination.
• Medicaid: varies by state; often 30 to 90 days.

Your appeal letter should state the patient's name, member ID, claim number, date of service, and a clear request for reconsideration. Attach:

1. A letter of medical necessity from your ordering doctor citing applicable guidelines (NCCN, ACR Appropriateness Criteria, or American College of Cardiology criteria for cardiac PET).
2. Relevant prior imaging reports, biopsy or pathology reports, and clinic notes that establish the clinical question.
3. Any peer-reviewed evidence supporting the use of PET for your specific indication.

Your ordering physician's office handles the bulk of this paperwork. Call them as soon as you get the denial — the sooner the appeal is filed, the more responsive the insurer tends to be.

Step 3: Request a Peer-to-Peer Review

A peer-to-peer review is a phone call between your ordering doctor and the insurance company's medical director. It is one of the most effective tools available and is frequently overlooked by patients.

Studies of utilization-management programs have found that peer-to-peer calls can resolve a meaningful share of denials without a formal written appeal — sometimes within 24 to 48 hours. The conversation lets your doctor explain the clinical reasoning directly, which is often more persuasive than a written letter.

Patients cannot request the peer-to-peer themselves; only the ordering physician can. Ask the doctor's office: "Can you request a peer-to-peer with the insurer's medical director on my behalf?" Most physicians are willing — they want their orders to go through.

Step 4: External Review (When Internal Appeals Fail)

If the internal appeal is denied, the Affordable Care Act guarantees the right to an external review by an independent third party for most plans. The reviewer is a medical professional unaffiliated with the insurer, and the decision is binding on the plan.

External review timelines:

• Standard external review: decision within 45 days.
• Expedited external review (when delay would jeopardize health): 72 hours.
• Filing window: typically 4 months (120 days) from the final internal denial.

Independent reviewers overturn insurer denials in a substantial share of imaging cases. To file, follow the instructions on the final internal denial letter, or contact your state insurance department, which often facilitates the process at no cost to you.

What If You Already Had the Scan and Cannot Pay?

Sometimes a scan is performed urgently and the denial arrives later, leaving the patient with the bill. In this situation:

• Negotiate with the imaging center directly. Ask the billing office for the cash-pay or financial-assistance rate, which is often a fraction of the billed amount.
• Request a payment plan. Most facilities offer 6 to 24 month no-interest plans.
• Ask about hospital financial assistance. Nonprofit hospitals are required by IRS rules to offer financial assistance policies (FAP); ask explicitly for the FAP application.
• Continue the appeal anyway. Even after paying, a successful appeal can refund what you paid out of pocket.

Special Note for Cancer Patients

The National Cancer Institute and ACS both note that cancer-related PET scans (initial staging, restaging after treatment, surveillance) typically have stronger insurance coverage than PET for non-cancer indications. If your PET was ordered as part of cancer staging or surveillance, your appeal letter should explicitly cite the NCCN guideline for your tumor type — these are widely accepted by insurers.

If anxiety while waiting on appeals is overwhelming, our guide on scanxiety: how to cope while waiting for results offers practical strategies.

Frequently Asked Questions

How long do I have to appeal a PET scan denial?

For most commercial plans, you have 60 to 180 days from the denial letter, depending on plan type. Medicare Part B gives 120 days for redetermination. Read the deadline on your specific letter — missing it forfeits the appeal.

What is the success rate of PET scan appeals?

Success depends on the strength of clinical documentation and which appeal level you reach. Internal appeals supported by NCCN or ACR guideline citations have a higher overturn rate, peer-to-peer calls resolve many cases informally, and external reviewers — who are independent of the insurer — overturn a meaningful share of imaging denials.

Can my doctor force the insurance company to approve the scan?

No insurer can be forced, but a strong letter of medical necessity, a peer-to-peer call, and (if needed) an external review are the standard escalation path. Doctors who write detailed clinical letters and engage in peer-to-peer calls have substantially higher approval rates than those who only resubmit the original order.

What if I need the PET scan urgently?

Ask your doctor to request an expedited (urgent) appeal, available when a delay would jeopardize your health. The insurer must respond within 72 hours, and the same expedited window applies to external review. Use this when a treatment decision is waiting on the result.

Should I pay the bill while appealing?

If you can avoid it, do not pay until the appeal is resolved — paying may not cancel the appeal, but it complicates accounting if you win. If you must pay to keep the account out of collections, request that the imaging center hold the account in "appeal pending" status, which most facilities will honor.

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• Prior Authorization for Medical Imaging: A Patient Guide
• Radiology Second Opinion: When to Ask for One

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Disclaimer: This article is for educational purposes only and does not constitute medical or legal advice. Always consult with a qualified healthcare professional for diagnosis and treatment decisions, and consider consulting an attorney or your state insurance department for complex insurance disputes.