What Is Prior Authorization and Why Do Insurers Require It?
Before certain medical services happen, many health plans require a green light from the insurer first. That extra step is called prior authorization, and it exists mostly to confirm a treatment fits the plan’s coverage rules before any bill is generated.
The short answer
Prior authorization is a process in which a health insurer reviews and approves a specific medical service, procedure, or prescription before it takes place, confirming that the treatment meets the plan’s coverage rules and is considered medically necessary. Without that approval, a service that might otherwise be covered can be denied outright or paid at a reduced rate.
Why insurers require it
Insurers frame prior authorization as a way to manage cost and quality at the same time.
- Cost control. Reviewing expensive services in advance lets an insurer confirm a lower-cost alternative hasn’t been overlooked before approving a pricier option.
- Medical necessity. The review checks whether the requested service matches clinical guidelines for the diagnosis involved, a process explored in more depth in how an insurer decides whether a treatment is medically necessary.
- Utilization patterns. Plans use authorization data to track how often certain services are requested, which can flag unusual patterns across a patient population rather than any single case.
Which services commonly require it
Not every visit or prescription needs prior sign-off. It tends to concentrate around higher-cost or higher-risk categories, including:
- Advanced imaging, such as an MRI or CT scan
- Certain prescription drugs, especially specialty or brand-name medications
- Planned hospital admissions and non-emergency surgeries
- Durable medical equipment and some out-of-network specialist referrals
Routine primary care visits and most emergency treatment generally fall outside this requirement, since emergencies by definition can’t wait for a review.
How the process generally works
A provider’s office typically submits the request on the patient’s behalf, including notes on diagnosis, the proposed treatment, and why it’s appropriate. The insurer then compares that information against its coverage criteria and clinical guidelines. Turnaround time varies by plan and by how urgent the request is, which is covered in more detail in how long prior authorization typically takes.
What happens if the step gets skipped
Receiving care without the required authorization doesn’t necessarily mean it will be paid for after the fact. Depending on the plan, the claim can be denied even if the treatment would have qualified had it been submitted in advance, leaving the patient responsible for the bill or facing a longer process to resolve it. When a request is turned down, whether before or after treatment, there’s usually a defined path forward, outlined in what to do if prior authorization is denied.
The takeaway
Prior authorization is essentially a checkpoint, not a judgment about whether care is appropriate — it exists so an insurer can confirm coverage terms are met before money changes hands. Because the requirement varies by plan and by service, checking directly with the insurer or provider’s office before a costly procedure is generally the more reliable way to avoid a surprise denial.