Why Does an MRI or CT Scan Often Require Prior Authorization?
Advanced imaging is often one of the first services people encounter prior authorization rules on, mostly because it’s expensive relative to a typical office visit and easy for a plan to review in advance.
The short answer
MRI and CT scans commonly require prior authorization because they are relatively high-cost services with well-established clinical guidelines about when they’re appropriate, making them a straightforward category for insurers to review before approving. The requirement is about confirming the scan fits accepted criteria for the symptoms or diagnosis involved, not about whether imaging in general is useful.
Why imaging draws extra scrutiny
- Cost relative to alternatives. An MRI or CT scan typically costs significantly more than many other diagnostic tools, which makes it a natural target for advance review.
- Established clinical guidelines. Because there’s substantial published guidance on when imaging is appropriate for specific symptoms, insurers can apply relatively standardized criteria, tying closely into how medical necessity gets determined for this category of service.
- Overuse concerns. Imaging is sometimes ordered as a precaution even when symptoms don’t clearly point to a need for it, and prior authorization is one way plans try to confirm the ordering rationale before approving.
The typical approval process
A doctor’s office ordering the scan generally submits the authorization request directly, including the specific symptoms, relevant history, and any prior tests or treatments already tried. The insurer compares that information against its clinical criteria for the requested type of scan and either approves, denies, or asks for more information. Because this process runs through established clinical checklists for common scenarios, straightforward cases are often resolved fairly quickly, while more unusual presentations may take longer or trigger a peer-to-peer review.
How much time it can add to scheduling
Depending on the plan and the urgency of the request, this review can take anywhere from same-day turnaround for urgent cases to a week or more for a standard, non-urgent request, a range covered in more detail in how long prior authorization typically takes. Because imaging is often scheduled at a separate facility from the ordering provider, any delay in the authorization step pushes back the earliest date the scan itself can be booked.
What can help avoid delays
- Submitting the request as early as possible relative to when the scan is needed, rather than close to a preferred date.
- Making sure the clinical documentation is complete the first time, since a request sent back for more information restarts part of the review.
- Confirming the request was received by the insurer, since a request that’s lost or incomplete on submission can sit unprocessed until someone follows up.
A grounding thought
Imaging tends to draw prior authorization attention simply because it sits at the intersection of high cost and well-documented clinical guidelines, not because insurers view it as unnecessary. Understanding that the review is checklist-driven, and building in extra scheduling time for it, makes the process less likely to catch a patient off guard.