Does Medicare Require Prior Authorization? A Complete Provider Guide

If you bill Medicare, or you are a beneficiary planning an upcoming procedure, the question on your mind is simple. Does Medicare require prior authorization? However, the answer will vary based on a person's Medicare coverage type and the specific service being requested. Original Medicare had no approval procedure for many years, and Medicare Advantage plans created their own set of regulations over the top of the basic benefit. That gap is now closing.

A new CMS pilot beginning in 2026 requires some providers to obtain approval before providing certain services, even for Original Medicare. This guide explains in detail what Medicare requires authorizations actually mean in reality, how it varies between Original Medicare and Medicare Advantage and what's new this year, as well as the steps a billing partner such as Gravita OASIS Review takes to ensure claims don't languish in the queue.

What Is Medicare Prior Authorization?

Medicare programs often use the requirement that the doctor or supplier provide evidence of medical necessity to Medicare (or a Medicare Advantage plan) before the service is rendered, as a mechanism for prior authorization. The reviewer verifies the request with the coverage rules and either approves the request, requests additional information or denies the request. The primary purpose of Medicare pre authorization is to ensure that services are medically necessary and that they are billed properly before it's paid for.

Not a referral; it doesn't mean the claim will be paid at some time in the future as the ultimate determination will be based on documents submitted with the claim itself. If a provider does not do this for a service that requires it, it most often results in a denied claim, or a frustrated patient.

Traditional Medicare vs. Medicare Advantage: Prior Authorization Rules

In the past, original Medicare (Part A hospital care and Part B medical services) was designed to allow beneficiaries to visit any provider who accepts Medicare without needing prior authorization. Prior authorization for Medicare Part A and B was the exception, and covered only a few services, including some kinds of durable medical equipment, some outpatient hospital care, and a few drugs.

Medicare Advantage (Part C) has been an exception. The plans are operated by private insurance plans and CMS gives them flexibility in determining their utilization management guidelines, as long as they do not result in coverage that is less than what Original Medicare provides. This distinction is what makes the two programs differ in terms of their reputations with patients and in the eyes of billing personnel.

Do Medicare Advantage plans require prior authorization?

Yes, in the general case, for a variety of non-emergency care. For Medicare Advantage members, you will need plan approval for every specific thing you need, such as inpatient hospital visits, skilled nursing facility visits, advanced imaging, durable medical equipment, some doctor visits besides specialty doctors, and many outpatient surgeries. The list is different for each plan, so a service that requires an approval from one might not require it in another.

New CMS Prior Authorization Rules for 2026: What Providers Should Know

Beginning January 1, 2026, Medicare introduced the six-year Wasteful and Inappropriate Service Reduction (WISeR) model, requiring prior authorization for about 17 services in selected states.The program integrates artificial intelligence with licensed health care professionals to review services that are deemed "low value" or over-used.

These are skin substitute grafts, epidural steroid injections, electrical nerve stimulators, knee arthroscopy for osteoarthritis, spinal fusion, bone cement injections and incontinence control devices. Providers need to continually check CMS guidance as the list may change throughout the pilot.

If you're wondering what procedures Medicare requires prior authorization for, remember the approved services may change over time. Standard requests are typically reviewed within 72 hours, while expedited requests are decided within 48 hours. Providers also retain their appeal rights if a request is not approved.

Which states will be affected by the new Original Medicare pilot program?

The WISeR pilot is currently limited to six states: Arizona, New Jersey, Ohio, Oklahoma, Texas, and Washington. Providers and suppliers in these states treating Original Medicare patients for the listed services have three options. They can send the request straight to the technology vendor assigned to their region, route it through their Medicare Administrative Contractor as they normally would, or skip the request and accept that the claim will go through a detailed post-service medical review instead.

CMS has said this program will not change coverage or payment rules, and it does not apply to inpatient-only services or emergencies. If the model expands after the pilot, more states and services could be added in future years, meaning Medicare will require prior approval for certain procedures well beyond the original 17.

How the Medicare Prior Authorization Process Works

Does Medicare require prior authorization for procedures across every contractor the same way? Not quite, since each Medicare Administrative Contractor and each Medicare Advantage plan can set its own list, but the steps to get an approval are fairly consistent. A provider gathers documentation showing the clinical reason for the service, including diagnosis codes, prior treatment attempts, and supporting test results.

Medicare Part B prior authorization requests for items like certain DME or outpatient procedures that are usually submitted electronically through a payer portal or faxed using a standard form. The reviewer compares the request against published coverage criteria, sometimes referred to as local or national coverage determinations.

Once a request is approved, a claim tracking number is created which must be listed on the claim and is allowed to be active for a certain time period (usually 120 days) before the service needs to be rescheduled and a new request submitted. Once a clinic has a checklist of sorts, Prior authorization Medicare staff handle every day seems routine, but in a one-off scenario it can seem like they're in a hurry to get it done.

What Happens If Medicare Prior Authorization Is Denied?

A denial is not the end of the road. Providers can resubmit with additional clinical notes, request a peer to peer conversation with the reviewing clinician, or proceed to a formal appeal through the standard Medicare appeals process.

Most programs, including the new WISeR pilot, place no limit on the number of times a request can be resubmitted before a service date. What does change is the patient experience, since a denial almost always means a delay in scheduling, and a billing team that has not built a clean documentation workflow will see more rework, more phone calls, and slower cash flow as a result.

How Gravita OASIS Review Streamlines Medicare Prior Authorizations

Handling prior authorization requests well takes more than knowing the rules. It takes a system. Gravita OASIS Review works alongside home health and outpatient billing teams to track which services on a payer's list require advance approval, gather the supporting documentation before a claim is submitted, and flag missing tracking numbers before they cause a rejection.

The team doesn't wait for denials to occur, but creates a checklist based on each payer's needs from a Medicare Advantage plan to a WISeR vendor in a pilot state to a standard Part B contractor. This means delayed services are kept to a minimum, fewer resubmissions and a claims process that moves at the pace your patients need.

Frequently Asked Questions (FAQs) on Does Medicare Require Prior Authorization?

Do you need prior authorization for Medicare Part B?

For most routine Part B services such as office visits and lab work, no approval is needed. Medicare Part A and B prior authorization has always been limited to a short list of items, including some outpatient procedures, certain drugs, and select durable medical equipment, and under the WISeR pilot, a small group of additional services in six states now need it too. Medicare pre authorization for these added services follows the same documentation rules as any other request.

Which procedures require Medicare Advantage pre-authorization?

Not exactly, since this varies by plan, but common categories include inpatient hospital admissions, skilled nursing stays, advanced imaging like MRI and CT, many outpatient surgeries, durable medical equipment, and some specialty drugs. Always check the specific plan's coverage list before scheduling.

How long does a Medicare prior authorization request take?

Standard requests are generally decided within a few business days, often around 72 hours under the new WISeR rules, while expedited requests tied to urgent medical need can be decided in 48 hours or less. Medicare Advantage plans follow their own timelines, which are set by CMS regulation.

Does Medicare Require Prior Authorization for Surgery?

It depends on the surgery and the plan. Not historically, but certain procedures on the WISeR list, such as knee arthroscopy and spinal fusion, now do in the six pilot states. Medicare Advantage plans frequently require approval for non-emergency outpatient and inpatient surgeries.

Does Medicare Require Prior Authorization for MRI or CT Scans?

Many Medicare Advantage plans do require it for advanced imaging, so it is worth confirming with the plan before the scan is scheduled. Medicare part b prior authorization rules have not historically reached most imaging orders, though that could change as CMS reviews the WISeR pilot results.

Does Medicare Require Prior Authorization for Home Health Services?

Home health agencies sometimes need to submit a pre-claim or pre-payment review request for episodes of care, depending on the state and the specific demonstration in effect. Medicare Advantage plans may add their own home health approval steps as well.

Does Medicare Pre-Authorization Guarantee Payment?

No. An approval confirms that a service meets medical necessity rules at the time of the request, but final payment still depends on accurate coding, complete documentation, and meeting all other billing requirements when the claim is actually submitted.