Most health insurance plans require prior authorization for outpatient MRI scans. This means your doctor’s office needs to get approval from your insurer before the scan is scheduled, or you risk paying the full cost out of pocket. The specifics depend on your insurance type, where the MRI is performed, and what state you live in.
When Prior Authorization Is Required
MRI falls into a category insurers call “advanced outpatient imaging,” alongside CT scans, PET scans, and similar procedures. Major insurers like UnitedHealthcare explicitly require prior authorization for outpatient MRIs. Most other large commercial plans follow the same pattern. The key word here is “outpatient,” meaning scans ordered by your doctor and performed at an imaging center or hospital outpatient department.
There are notable exceptions. Authorization is typically not required for MRIs performed during an emergency room visit, an urgent care visit, or while you’re admitted as an inpatient. If you’re referred for an MRI directly from an emergency department, that referral also generally bypasses the prior authorization requirement. Medicare Advantage and certain dual special needs plans don’t require prior authorization for MRIs, CTs, or similar scans at all. Traditional Medicare covers MRI as long as it’s considered reasonable and necessary for your specific diagnosis, without a separate authorization step.
What Insurers Look For
When your doctor submits a prior authorization request, the insurer evaluates whether the MRI is medically necessary for your situation. This isn’t a rubber stamp. The insurer wants to see that the scan will directly help diagnose or treat your condition, and in some cases, that simpler or cheaper tests were tried first.
That said, the rules aren’t as rigid as people sometimes fear. For example, Medicare’s national coverage policy specifically states that MRI can be covered for diagnosing disc disease without requiring that X-rays or other imaging be tried first. If your doctor has a clear clinical reason for ordering the scan, that’s often sufficient. Problems tend to arise when the submitted paperwork is incomplete or when the clinical notes don’t clearly explain why the MRI is needed.
Who Handles the Paperwork
Prior authorization is your doctor’s responsibility, not yours. Your physician’s office submits the request, provides clinical documentation, and follows up with the insurer. In practice, many medical offices have dedicated staff who do nothing but handle prior authorization paperwork. The average physician in the U.S. processes roughly 45 prior authorization requests per week, according to the American Medical Association.
Your role is limited but important. If your doctor’s office schedules an MRI, ask whether prior authorization has been obtained before your appointment. If you show up for a scan without approval, the imaging center may cancel the appointment or proceed knowing you could be billed directly. Some imaging centers will check authorization status themselves, but don’t assume this happens automatically.
How Long Approval Takes
Turnaround times vary significantly by state and by insurer. There’s no single national standard, but many states have passed laws capping how long insurers can take to respond.
- California: 5 business days for non-urgent requests, 72 hours for urgent ones
- Colorado: 15 days for non-urgent, 72 hours for urgent
- Washington, D.C.: 3 business days if submitted electronically, 5 business days by phone or fax
In states without specific laws, insurers set their own timelines, which can stretch longer. Urgent requests, where a delay could seriously harm your health, are processed faster everywhere. If your doctor marks the request as urgent, expect a decision within a few days at most. For routine requests, plan for one to two weeks in many cases, though some approvals come back within 48 hours.
Delays are common when additional documentation is needed. If the insurer comes back asking for more clinical notes, the clock essentially resets. This is one of the most frustrating parts of the process: your doctor may have done everything right, but the office is stuck waiting on the insurer to respond.
What Happens If You’re Denied
A denial doesn’t necessarily mean the MRI won’t happen. It means the insurer doesn’t think the current documentation supports medical necessity. Your doctor can appeal the decision, and many denials are overturned on appeal when additional clinical information is provided. Physicians frequently fight these rejections, and the AMA has described the appeals process as a significant part of doctors’ administrative workload.
If your authorization is denied and your doctor believes the MRI is essential, ask the office whether they plan to appeal. You can also request a copy of the denial letter, which will explain the insurer’s reasoning and outline your rights to appeal on your own. Some states require insurers to provide an independent external review if the internal appeal fails.
Changes Coming in 2026 and 2027
The federal government has finalized new rules aimed at making prior authorization faster and more transparent. Starting January 1, 2026, insurers covering Medicare, Medicaid, and marketplace plans must begin implementing reforms, including publicly reporting how often they approve or deny requests and how long decisions take. By January 1, 2027, these insurers must support electronic prior authorization systems designed to speed up the process and reduce the back-and-forth that currently causes delays.
These rules won’t eliminate prior authorization for MRIs, but they should make the timeline more predictable and give patients better visibility into where their request stands.