Prior Authorization: How the Approval Process Works for Patients

Prior authorization is one of the most consequential — and most misunderstood — steps in the American healthcare delivery chain. It's the formal process by which a health insurer reviews and approves (or denies) a treatment, medication, or procedure before that service is provided. The stakes are real: the American Medical Association has reported that 94% of physicians say prior authorization delays patient care, and 33% say delays have led to serious adverse events for their patients. Understanding how this process works gives patients a meaningful advantage when navigating it.

Definition and scope

Prior authorization — sometimes called preauthorization, precertification, or prior approval — is a utilization management tool embedded in most commercial health insurance plans, Medicare Advantage plans, and Medicaid managed care programs. It requires that a treating clinician obtain insurer approval before delivering certain services, or the insurer may refuse to pay.

The scope is broader than most patients expect. As documented in the health insurance navigation for patients framework, prior authorization requirements can apply to specialty medications, outpatient imaging (MRI, CT, PET scans), elective surgical procedures, durable medical equipment, inpatient admissions, certain behavioral health treatments, and even some laboratory tests. A standard commercial plan may subject hundreds of distinct service codes to review.

What prior authorization is not is a medical second opinion. The insurer is not evaluating whether the treatment is a good idea clinically in the abstract — it is evaluating whether that treatment meets the plan's coverage criteria, which are defined by the insurer's internal clinical policy documents, not by the treating physician's judgment alone.

How it works

The mechanics follow a predictable sequence, though the timeline and complexity vary by plan and service type.

1. Prescribing or ordering physician submits a request — either through the insurer's online portal, by fax, or by phone, along with clinical documentation supporting the medical necessity of the service.
2. Insurer assigns a reviewer — most routine requests go to a nurse or clinical reviewer first, not a physician.
3. Initial determination is issued — under federal Medicaid managed care rules (42 CFR § 438.210) and the requirements governing Medicare Advantage plans (CMS regulations at 42 CFR § 422.568), urgent prior authorization decisions must be issued within 72 hours; standard decisions within 14 calendar days for Medicaid managed care.
4. Approval, denial, or request for additional information — if additional documentation is requested and not received within the plan's window, the request may be closed without a decision.
5. Appeals process triggers if denied — a denial is not a final answer. Patients and providers have the right to appeal, and for cases with an active denial, an expedited external review can sometimes be completed within 72 hours under federal standards established by the Affordable Care Act.

The treating provider's office typically drives this process, but patients can — and often should — monitor it actively. Resources like patient advocacy services exist precisely to help when the process stalls.

Common scenarios

Three situations account for a disproportionate share of prior authorization friction in practice.

Specialty pharmaceuticals. A drug on an insurer's specialty tier — biologics for rheumatoid arthritis, oncology agents, MS treatments — almost always requires prior authorization and, in many cases, documented evidence that the patient has already tried and failed at least one lower-cost alternative. This is called a "step therapy" or "fail first" requirement. Step therapy protocols are now regulated in at least 32 states, according to the National Alliance on Mental Illness (NAMI), which tracks these policies specifically for behavioral health prescriptions.

Imaging and diagnostics. An orthopedist who orders an MRI for a patient with knee pain may find that the insurer requires documentation of a prior trial of conservative management (physical therapy, anti-inflammatories) before approving the scan. This can delay diagnosis by weeks for patients managing chronic disease or recovering from injury.

Inpatient and post-acute care. A hospitalized patient being discharged to a skilled nursing facility, inpatient rehabilitation, or home health program will often require separate prior authorization for that transition. The discharge planning services process is closely intertwined with these requirements — a delay in authorization can extend a hospital stay or disrupt a carefully coordinated transitional care plan.

Decision boundaries

Two distinct frameworks govern how authorization decisions get made, and the difference matters when a denial arrives.

Internal review applies the insurer's own clinical coverage criteria. These criteria reference evidence-based guidelines — CMS coverage determinations, InterQual criteria, Milliman Care Guidelines — but the insurer's interpretation of those guidelines is proprietary. Internal reviewers are bound by the plan's policy documents, which may be more restrictive than what a treating physician considers standard of care.

External review is conducted by an Independent Review Organization (IRO) that has no financial relationship with the insurer. Under the ACA's external review provisions, codified at 45 CFR § 147.136, non-grandfathered individual and group health plans must provide access to an accredited IRO. External reviewers apply generally accepted standards of medical practice — not the insurer's internal criteria — which is why external review overturn rates for denials can reach 40% or higher in certain categories, according to data compiled by the Kaiser Family Foundation.

Patients whose requests involve experimental or investigational treatments face a harder boundary: most plans explicitly exclude unproven treatments, and neither internal nor external reviewers typically override that categorical exclusion. The path forward in those cases usually involves clinical trials, compassionate use programs, or patient financial assistance programs that operate outside the insurance structure entirely.

Understanding where each decision gets made — and by what standard — is the single most useful piece of information a patient can hold when a prior authorization request is denied. The process has real rules, and those rules have real leverage points. Knowing them changes the conversation.