Your MRI or CT Scan Was Denied by Insurance. Here's How to Win

Your back has hurt for two months. Your doctor examined you, said the words "let's get an MRI," and you left relieved that someone was finally taking it seriously. Then the letter came: not medically necessary. It stings, and it reads like a final verdict. It isn't. Advanced imaging is the single most prior-auth-gated service in outpatient medicine, most imaging denials are paperwork failures rather than medical judgments about you, and paperwork failures are winnable on paperwork.

Why did your insurance deny an MRI your doctor ordered?

Most plans don't review imaging requests themselves. They contract it out to a radiology benefit manager (RBM) such as EviCore or Carelon, whose reviewers check the request against written clinical guidelines: has the patient tried conservative treatment, do the symptoms match the criteria for this study, is this the study the guideline calls for. If the request as submitted doesn't check every box, it gets denied, even when the missing box is something you actually did that never made it into the paperwork. That's why the denial letter can feel so disconnected from your visit: the reviewer never saw your visit. They saw a form.

The four usual reasons an MRI or CT gets denied

• Conservative treatment wasn't documented first. For low back pain, guidelines typically want several weeks of physical therapy, anti-inflammatories, or home exercise before an MRI. If you did six weeks of PT last year and nobody wrote it in the request, the reviewer scores it as never tried.
• Clinical notes were missing or thin. The request went in without the exam findings, the symptom timeline, or the red flags that justify imaging. The reviewer can only approve what's on the page.
• The "wrong" study was ordered per the guideline. The plan's criteria may call for a CT before an MRI, or a study without contrast instead of with it. This is a fixable mismatch between the order and the checklist, and your doctor can either switch or argue the exception.
• Site-of-care steering. Some plans approve the scan itself but deny it at a hospital-based facility, pushing you to a freestanding imaging center instead. Read the letter carefully: this is a denial of the *place*, and rebooking the same scan at an approved center resolves it.

How to get a denied MRI approved, in order

1. Ask the ordering office exactly what the reviewer said was missing. The office received a denial with a specific reason and often a reference number for the guideline used. "Not medically necessary" on your letter usually translates to one concrete missing item on theirs.
2. Get the conservative-care history into the chart and resubmit. If the gap is undocumented PT, chiropractic care, medications, or home treatment, tell the office everything you've tried with dates. A corrected resubmission is often approved in days, no appeal needed.
3. Request a peer-to-peer review before the denial finalizes. This is your doctor speaking directly with the plan's reviewing physician, and it reverses a large share of imaging denials in a single call. The window to request one can be short, so push the office to schedule it now. The peer-to-peer guide covers how to make that call count.
4. File a formal appeal that answers the guideline point by point. Ask the plan for the specific clinical criteria it used (you're entitled to them), then have your doctor's letter address each criterion with your dates, findings, and failed treatments. The appeal guide walks through deadlines and the external review that follows if the plan says no again.

How long does MRI prior authorization take?

Routine imaging prior auth commonly takes anywhere from a day to about two weeks, depending on the plan and whether the request was complete the first time. Two useful anchors: a federal rule that took effect in 2026 requires Medicare Advantage, Medicaid, and marketplace plans to answer standard prior auth requests within 7 calendar days and expedited requests within 72 hours. And for denials of care you haven't received yet, the plan must decide a standard internal appeal within 30 days. If nothing has moved in a week, call and ask for the status and the reference number. The prior authorization guide explains the whole pipeline.

The urgent path is different. If waiting the standard timeline could seriously endanger your health (suspected cancer, progressive neurological symptoms, anything your doctor is genuinely worried about), ask for expedited handling at every stage: expedited prior auth decision, expedited internal appeal, and expedited external review, which can be decided in as little as 72 hours and can even run at the same time as the internal appeal. The magic ingredient is a statement from your doctor that the delay is dangerous. Ask them to say exactly that, in writing.

The cost move, even after approval

An approval decides whether the plan pays its share. It does not decide what the scan costs, and the spread is enormous: the same MRI often runs several times more at a hospital-based facility than at a freestanding imaging center, which matters directly to you if you're in your deductible or paying coinsurance. Before you book, look up what nearby facilities charge, and ask any imaging center for its cash price, which is a legitimate question even when you're insured. Sometimes paying the self-pay rate beats using your insurance entirely. Ten minutes of comparison can save hundreds of dollars on a scan that's identical either way.