Javascript is not enabled.

Javascript must be enabled to use this site. Please enable Javascript in your browser and try again.

Skip to content
Content starts here
Leaving Website

You are now leaving and going to a website that is not operated by AARP. A different privacy policy and terms of service will apply.

What is prior authorization in Medicare?

Prior authorization is preapproval for medical services or prescription drugs that health insurance plans often require before they will cover the cost.

How often and under what circumstances prior authorization is required depends on the health plan. While Original Medicare has a few preapproval requirements, private Medicare Advantage plans and Part D prescription drug plans use this procedure more often.

spinner image Image Alt Attribute

AARP Membership— $12 for your first year when you sign up for Automatic Renewal

Get instant access to members-only products and hundreds of discounts, a free second membership, and a subscription to AARP the Magazine.

Join Now

A provider or supplier typically must complete and submit forms to a health plan to verify the need for a specific drug, piece of equipment or service. Plans put these requirements in place to avoid paying for unnecessary services or expensive procedures and drugs when a lower-cost version that works just as well may be available. Patients also will know ahead of time if their plan will approve something that’s not always covered rather than having to appeal a denial afterward.

Prior authorization requirements vary by type of plan and insurer. 

What is prior authorization in Original Medicare?

Original Medicare rarely requires prior authorization. The government program generally covers medically necessary services without requiring you or your doctor to submit special forms in advance or even a referral to see a specialist.

In the few instances when authorization is needed, a Medicare administrative contractor (MAC) reviews the request and makes a decision.

Original Medicare prior authorization

Original Medicare requires prior authorization only for three types of services. In 2022, most of the requests were approved in an average of about four days. 

Outpatient services, primarily dermatology

Percentage approved: 78.6 percent
Average time: 4.5 days
Denials overturned on appeal: 0.3 percent  

Durable medical equipment

Percentage approved: 66.9 percent
Average time: 4.7 days
Denials overturned on appeal: 0.3 percent 

Nonemergency ambulance services

Percentage approved: 63.2 percent
Average time: 4.1 days
Denials overturned on appeal: 3.9 percent 

Source: Centers for Medicare & Medicaid Services

What is prior authorization in Medicare Advantage?

Prior authorization requirements are much more common in Medicare Advantage plans. A study from health researchers KFF, formerly the Kaiser Family Foundation, found that almost all Medicare Advantage enrollees in 2023 — 99 percent — are in plans that require prior authorization for some services.  

Some of the most common services requiring prior authorization for Medicare Advantage plans include: 

  • Part B drugs: Medications generally taken in a doctor’s office, where 99 percent of enrollees are in Advantage plans that require preapproval
  • Durable medical equipment: 99 percent
  • Skilled nursing facility stays: 99 percent
  • Sudden, short-term inpatient hospital stays, called acute care: 98 percent
  • Psychiatric inpatient hospital stays: 93 percent
  • Diagnostic lab work and tests: 92 percent
  • Home health services: 91 percent

While only 7 percent of Advantage enrollees must get prior authorization for preventive services, knowing what your plan requires can keep you from facing unexpected charges. 

Medicare Advantage plans are prohibited from applying prior authorization requirements on emergency services, and they must disclose prior authorization rules and other review requirements to enrollees. Before choosing a Medicare Advantage plan, read the plan’s evidence of coverage (EOC) to find out more about its prior authorization rules.  

In 2022, the U.S. Department of Health and Human Services Office of Inspector General studied a random sample of 250 prior authorization denials that 15 of the largest Medicare Advantage plans issued from June 1-7, 2019. The government found that Original Medicare likely would have covered 13 percent of the services denied.

Starting in 2024, the Centers for Medicare & Medicaid Services (CMS) is requiring Medicare Advantage plans to streamline their prior authorization process to ensure that people with Medicare Advantage receive access to the same medically necessary care they would receive in Original Medicare.  


AARP® Vision Plans from VSP™

Exclusive vision insurance plans designed for members and their families

See more Insurance offers >

What is prior authorization in Medicare Part D?

Many Part D prescription drug plans require prior authorization before they will cover expensive specialty drugs; medicines that may be misused, such as some cannabis-derived medications; or drugs that may be used in ways that aren’t FDA-approved, such as Ozempic, which Medicare covers for diabetes but not weight loss.  

You or your prescriber must contact the plan to show the drug is medically necessary before you can fill certain prescriptions.  

A list of drugs that require prior authorization is available in a Part D plan’s documents. Or you can see if plans in your area have restrictions on your medications by entering your drugs and doses into the Medicare Plan Finder.

Keep in mind

Appealing a prior authorization denial can be worthwhile, especially with Medicare Advantage plans.   

More than 35 million prior authorization requests were submitted to Medicare Advantage plans in 2021, and insurers denied more than 2 million of these requests fully or partially, KFF found. Only 11 percent of these denials were appealed; 82 percent of the appeals resulted in full or partial overturning of the denial. 

Contact your Medicare Advantage insurer for the steps to appeal. The standard appeal can take up to 14 days, but the plan must make an expedited decision in 72 hours if your doctor tells your plan that waiting may jeopardize your health. 

For more information about appealing each type of prior authorization denial, see the Medicare appeals resource at 

Return to Medicare Q&A main page

Discover AARP Members Only Access

Join AARP to Continue

Already a Member?