Which services require prior authorization
There is no single national list of services that require prior authorization. Each payer and plan defines its own requirements, and those requirements most often target services that are high-cost, elective, or prone to wide variation in use — advanced imaging, elective inpatient admissions, certain outpatient surgeries, durable medical equipment, specialty drugs, and selected diagnostic tests are recurring examples. Because every list is set by contract and revised on its own schedule, the only reliable answer for a specific patient is the requirement the patient's payer publishes for that plan on the date of service.
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Key takeaways
- No universal list exists; each payer and plan sets and updates its own prior-authorization requirements.
- Requirements cluster around high-cost, elective, and high-variation services rather than emergency care.
- The same service can require authorization under one plan and not another, and the rules change over time.
- Confirming the requirement is part of eligibility and financial clearance, completed before the service is furnished.
- A missing or mismatched authorization is a common, and often preventable, cause of denial.
How payers decide which services to gate
Prior authorization is a utilization-management control. A payer uses it to confirm, before a service is furnished, that the service meets the plan's coverage rules and medical necessity criteria. It is a coverage and payment decision, not a clinical judgment about whether care should happen — a clinician may still proceed, but the plan may decline to pay when an approved request is required and absent. Understanding that distinction is the starting point for identifying which services carry the requirement; for the broader concept, see what prior authorization is.
Because each payer builds its own program, the scope differs across commercial plans, Medicare Advantage, and Medicaid managed care. Payers commonly apply the requirement where cost, safety, or appropriateness concerns are highest, and where clinical guidelines support reviewing the request against documented criteria before the service is delivered.
- Prior authorization
- Advance approval of a specific planned service before it is furnished, based on the plan's coverage and medical-necessity criteria.
- Precertification
- A term many payers use interchangeably with prior authorization; the label varies but the underlying review is similar.
- Predetermination
- A voluntary, advance estimate of how a service would be covered, which does not guarantee payment.
- Step therapy
- A requirement to try lower-cost or first-line options before a requested drug or therapy is approved.
Service categories that commonly require authorization
While the exact list is payer- and plan-specific, several categories appear across many programs. The groupings below describe common patterns, not a universal rule — a service in one of these categories may or may not require authorization under any given plan.
- Advanced diagnostic imaging — MRI, CT, PET, and nuclear studies are frequently gated because of cost and ordering variation.
- Elective and non-emergent inpatient admissions, along with many scheduled surgical procedures.
- Selected outpatient procedures and ambulatory surgeries, particularly those performed in higher-cost settings.
- Durable medical equipment, prosthetics, orthotics, and supplies, especially higher-cost, custom, or rented items.
- Specialty, injectable, and infused medications billed under either the pharmacy or the medical benefit.
- Behavioral health services such as inpatient psychiatric care, residential treatment, and intensive outpatient programs.
- Post-acute and home-based care, including skilled nursing, home health, and rehabilitation services.
- Genetic and molecular testing, sleep studies, and certain cardiac or high-cost diagnostic tests.
- Out-of-network services, which many plans route through a separate review distinct from an in-network referral requirement.
Categories are a starting point, not a ruling
Related review mechanisms to distinguish
Not every advance-review requirement is a prior authorization, and payers use overlapping vocabulary. Distinguishing the mechanisms helps determine what a service actually needs and what an approval means for payment.
| Mechanism | What it reviews | Typical timing |
|---|---|---|
| Prior authorization | Whether a specific planned service meets the plan's coverage and medical-necessity criteria. | Before the service is furnished. |
| Step therapy | Whether lower-cost or first-line options were tried before a requested drug or therapy is approved. | Before approving the requested option, often within pharmacy review. |
| Predetermination | A voluntary, advance estimate of how a service would be covered, without guaranteeing payment. | Before service, at the provider's or member's request. |
Terms such as precertification, precert, and pre-authorization often describe the same process; see how these terms compare. The label matters less than the plan's published requirement.
How to confirm the requirement for a specific service
Because the requirement attaches to the plan and the date of service, confirmation is a repeatable process rather than a memorized list. It typically runs alongside eligibility and financial clearance, and feeds directly into the authorization workflow.
Verify eligibility and the exact plan
Confirm active coverage and the specific plan or product, since requirements vary by plan and not just by payer.Check the payer's authorization requirement list or tool
Most payers publish a lookup tool or requirement list keyed to services and settings, updated periodically.Identify who is responsible for submitting
Responsibility varies — the ordering provider often submits, while the rendering or facility provider may carry the denial risk.Assemble the clinical documentation
Gather the records the plan's criteria call for; see gathering documentation.Submit before the service and record the decision
Capture the authorization number with approved units and dates when the request is submitted and returned.
Why the list varies, and why it matters for billing
Requirements vary by payer, plan, product line, and — for Medicaid and other state-regulated programs — by jurisdiction. They also change over time as payers revise their programs and as federal rulemaking evolves, including work under the CMS Interoperability and Prior Authorization rule. Any list should be treated as current only as of the date it was checked against the authoritative source.
Emergency care is generally handled differently
The billing consequences are direct. When a required authorization is missing, expired, or does not match what was billed, the result is often a denial. Even an approved request can lead to lost revenue if the approved service, units, or dates do not align with the claim, which is why matching authorized units to billed services and preventing authorization-related denials are core parts of the process rather than afterthoughts.
Common questions
Is there a standard list of services that always require prior authorization?
No. Requirements are set by each payer and plan and revised over time, so a service may require authorization under one plan and not another. The authoritative answer is whatever the specific payer publishes for that plan on the date of service.
Do emergency services require prior authorization?
Emergency and urgent care are generally treated under different rules than routine advance approval, but the specifics vary by payer, plan, and circumstance. Requirements should still be verified rather than assumed.
Does Medicare require prior authorization?
Original Medicare applies prior authorization to a limited set of items and services, while Medicare Advantage plans set their own, often broader, requirements. Both change over time and should be confirmed per plan against current CMS and plan sources.
If a service is medically necessary, is authorization automatic?
No. Medical necessity is one criterion the plan evaluates, but in most cases the request must still be submitted and approved before the service. Necessity supports the request; it does not replace it.
Who is responsible for obtaining the authorization?
It varies by service and payer. The ordering provider frequently submits the request, but the rendering or facility provider may bear the denial risk, so responsibility should be confirmed for each situation.
Key terms in this article
Defined once, on their own pages.
Continue learning
Where to go next within the prior authorization cluster.
What is prior authorization?
The foundational concept behind every requirement list.
Precertification, predetermination, and prior authorization
How the overlapping payer vocabulary differs in practice.
The prior authorization workflow
The end-to-end process from requirement check to decision.
Prior authorization for medications
How drug requirements and step therapy work under pharmacy and medical benefits.
Prior authorization under Medicare Advantage
Why plan-set requirements differ from Original Medicare.
Authoritative sources
- Centers for Medicare & Medicaid Services (CMS) (opens in a new tab)
Administers Medicare and Medicaid and publishes prior authorization and coverage policy.
- National Committee for Quality Assurance (NCQA) (opens in a new tab)
Accredits health plans and sets utilization-management standards that shape how prior authorization is conducted.
- Healthcare Financial Management Association (HFMA) (opens in a new tab)
Professional body publishing guidance on revenue cycle and utilization-management practices.