Why does Aetna require prior authorization for an MRI?

Aetna uses radiology benefit management (often eviCore) to check advanced imaging against clinical criteria, which usually expect documented conservative treatment first.

What if my doctor says the MRI is urgent?

Ask for an expedited appeal. If waiting could seriously jeopardize your health, the plan generally must decide within 72 hours.

Guides · Aetna · appeals · Updated July 2026

How to appeal an Aetna MRI or imaging denial

Aetna routes advanced imaging like MRIs, CTs, and PET scans through a radiology benefit manager that applies strict prior-authorization criteria. Many denials come down to one missing step — conservative treatment first — that your records can often show you already met.

Why Aetna denies this

Aetna commonly denies advanced imaging as "not medically necessary" when its prior-authorization criteria (often administered through eviCore) expect documented conservative treatment first — for example, several weeks of physical therapy or medication before an MRI for back pain. The denial usually reflects thin documentation of that earlier care, not the absence of it.

What wins the appeal

Submit records showing the conservative care you already tried (PT visits, medications, injections) and how long, plus any red-flag symptoms that justify skipping ahead (neurological deficits, suspected cancer, trauma). Ask for the exact clinical criteria used and match your documentation to each point. File within 180 days (65 for Medicare Advantage).

Your deadline

Depends on your plan type: 180 days for most employer and marketplace plans, 120 for Original Medicare, ~90 for Medicaid, and only 65 for Medicare Advantage. Set it before you do anything else.

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Common questions

Why does Aetna require prior authorization for an MRI?: Aetna uses radiology benefit management (often eviCore) to check advanced imaging against clinical criteria, which usually expect documented conservative treatment first.
What if my doctor says the MRI is urgent?: Ask for an expedited appeal. If waiting could seriously jeopardize your health, the plan generally must decide within 72 hours.