Does Medicare Require Prior Authorization for Outpatient Surgery?

For most outpatient surgeries, Medicare does not require prior authorization. Original Medicare requires it only for a specific list of procedures performed in a hospital outpatient department, currently eight categories. If you’re in a Medicare Advantage plan, the answer is different: those plans routinely require prior authorization for a much wider range of outpatient surgeries, and the rules depend on the plan.

Which Outpatient Surgeries Original Medicare Flags

CMS has phased in the list since 2020. As of 2026, these are the procedure categories that need approval before Medicare will pay when they’re done in a hospital outpatient department:

Blepharoplasty (eyelid surgery), botulinum toxin injections, panniculectomy, rhinoplasty, and vein ablation (added July 1, 2020).
Implanted spinal neurostimulators and cervical fusion with disc removal (added July 1, 2021).
Facet joint interventions (added July 1, 2023).

Nothing new was added for 2024, 2025, or 2026.¹ CMS updates the list through its annual Outpatient Prospective Payment System final rule, so check before your scheduled date if your procedure is anywhere near this territory.²

If your surgery isn’t on this list, Original Medicare does not require prior authorization for it. Medical necessity still applies, but the review happens when the claim is submitted, not before the procedure.

Hospital Outpatient Department vs. Surgical Center

Where the surgery happens changes the answer. The Original Medicare requirement applies only in hospital outpatient departments. The same procedure performed at a freestanding ambulatory surgical center does not trigger mandatory prior authorization. CMS runs a separate voluntary demonstration for certain ASC services, but skipping that one does not block payment.

A vein ablation at a hospital outpatient department needs approval first. The same vein ablation at an ASC across the street does not. Your surgeon’s office should know which setting applies, but it’s worth asking directly before scheduling.

How the Request Works

Your provider submits the request, not you. The surgeon’s office or hospital sends documentation to the Medicare Administrative Contractor (MAC) for your region, including your medical history, diagnosis codes, the treatment plan, and procedure codes.³ Prior authorization moves the medical-necessity review earlier; it does not add new documentation.

The MAC has 7 calendar days to issue a standard decision. If waiting would put your health at serious risk, your provider can request an expedited review, with a decision in up to 2 business days.¹

The MAC returns one of three answers: provisional affirmation (approved), provisional partial affirmation (some services approved, others not), or non-affirmation (denied). An affirmation comes with a Unique Tracking Number your provider attaches to the eventual claim.³ “Provisional” matters: Medicare is very likely to pay, but the MAC can still review the claim at billing.

Approvals are good for 120 days from the decision date, counting the decision date as day one. Approval on January 1 covers service dates through April 30. If the surgery slips past that window, the provider has to submit a fresh request.³

If the Request Is Denied

A non-affirmation is not the end. The MAC must spell out what was missing or which coverage, coding, or payment rule wasn’t met.³ Your provider then has two paths:

Resubmit with additional or corrected documentation. There’s no cap on how many times a provider can resubmit, and resubmissions get a decision in 5 business days.
Submit the claim anyway with the non-affirmation tracking number. The claim will be denied, which opens formal appeal rights through the standard Original Medicare appeals process.⁴

Most denials come from documentation gaps rather than genuine coverage disputes, so resubmission usually resolves the issue faster than an appeal.

The ABN Protects You From Surprise Bills

If your provider expects Medicare to deny a service for lack of medical necessity, they’re supposed to give you an Advance Beneficiary Notice of Noncoverage before the procedure. The ABN warns you Medicare probably won’t pay and asks whether you still want the service knowing you’d owe the cost. When a provider fails to issue an ABN in situations where one was required, Medicare holds the provider financially responsible, not you.

Medicare Advantage Is a Different World

Everything above describes Original Medicare (Parts A and B). If you’re in a Medicare Advantage plan, expect a much broader prior authorization requirement. Private insurers running these plans typically gate many more outpatient surgeries behind approval than the eight OPD categories on the Original Medicare list.⁵

Medicare Advantage plans must cover every medically necessary service Original Medicare covers, but they can layer their own prior authorization rules on top. Each plan sets its own list, its own submission process, and its own network rules. Before scheduling any outpatient surgery under a Medicare Advantage plan, check your Evidence of Coverage or call the plan. The requirement can vary by plan and sometimes by the specific contract your plan holds with a given hospital or surgeon.

If your Medicare Advantage plan denies prior authorization, you have 65 calendar days from the denial notice to request a reconsideration directly from the plan. For urgent pre-service situations, the plan must issue an expedited decision within 72 hours.⁶

Emergency Care Never Requires Prior Authorization

No Medicare plan, Original or Advantage, can require prior authorization for emergency services. Under 42 CFR 422.113, a Medicare Advantage plan is financially responsible for emergency and urgently needed services whether or not the enrollee got prior authorization, and plans are prohibited from telling enrollees or providers otherwise.⁷ If you land in an emergency room and end up needing surgery, prior authorization does not apply to that encounter.

What Changed for 2026

The CMS Interoperability and Prior Authorization Final Rule (CMS-0057-F) tightens the process starting January 1, 2026, mostly for Medicare Advantage, Medicaid managed care, and other “impacted payers”:

Denials must include a specific reason, regardless of how the request was submitted (portal, fax, email, mail, or phone). Drug authorizations are excluded.
Standard decisions must come within 7 calendar days and expedited decisions within 72 hours.
Impacted payers must report their first set of prior authorization performance metrics by March 31, 2026.⁸

For Original Medicare OPD services, the shift from 10 business days to 7 calendar days for standard decisions already took effect January 1, 2025, so the 2026 changes mainly help people in Medicare Advantage and other managed care plans.¹

1
Centers for Medicare & Medicaid Services. Prior Authorization for Certain Hospital Outpatient Department (OPD) Services
2
CMS. Final List of Outpatient Department Services That Require Prior Authorization
3
Centers for Medicare & Medicaid Services. Prior Authorization Process for Certain Hospital Outpatient Department (OPD) Services – Frequently Asked Questions
4
Medicare.gov. Appeals in Original Medicare
5
Medicare.gov. Compare Original Medicare and Medicare Advantage
6
Centers for Medicare & Medicaid Services. Reconsideration by the Medicare Advantage (Part C) Health Plan
7
eCFR. 42 CFR 422.113 Special Rules for Ambulance Services, Emergency and Urgently Needed Services, and Maintenance and Post-Stabilization Care Services
8
Centers for Medicare & Medicaid Services. CMS Interoperability and Prior Authorization Final Rule CMS-0057-F