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Medicare Prior Authorization Explained

Summary: Medicare prior authorization is a process used by Medicare to ensure that certain medical services or prescription drugs meet specific criteria for coverage before they are approved and paid for. The purpose of prior authorization is to ensure that treatments are medically necessary, helping to control costs and prevent unnecessary healthcare services.  Estimated Read Time: 7 min

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Table of Contents:

    1. What is Prior Authorization for Medicare?
    2. Medicare Part A Prior Authorization
    3. Medicare Part B Prior Authorization
    4. Medicare Part D Prior Authorization
    5. Medicare Advantage Prior Authorization
    6. How Do I Get Prior Authorization for Medicare?
    7. How Long Does it Take to Get Prior Authorization?
    8. Medicare Prior Authorization FAQs
    9. Getting Help Understanding Prior Authorization

Before your doctor can provide certain services, prior authorization from Medicare may be necessary. Depending on the Medicare plan you are enrolled in, you might need prior approval to see a specialist, have a procedure, or receive certain medications.

So, which services and plan types require prior authorization? Below, we’ll explain what you need to know.

What is Prior Authorization for Medicare?

Prior authorization is the process in which your doctor or care provider must receive approval from Medicare before they can be sure a service will be covered by your plan. This requirement is in place to ensure that the services or medications you receive are medically necessary and appropriate for your condition.

Typically, prior authorization is required for services or medications that are either expensive, elective, or often overused. The prior authorization process involves your healthcare provider submitting documentation to Medicare to determine the medical necessity of the service or medication they wish to provide you with.

Once the doctor submits their request, Medicare will review the submission and decide whether to approve or deny coverage. If approved, Medicare will cover its portion of the cost for the service or medication.

If the prior authorization is denied, the patient or healthcare provider may have the option to appeal the decision. However, a denial may also end in the patient being responsible for 100% of the cost if the appeal is denied.

Medicare Part A Prior Authorization

Medicare Part A covered services rarely require prior authorization. However, if you must submit a prior authorization for a Part A covered service, you can obtain the forms to send to Medicare from your hospital or doctor. Often your hospital will send the documents themselves. But it is important to understand who is responsible for sending the paperwork, so the responsibility does not slip through the cracks.

Examples of Medicare Part A. Services that may require prior authorization include:

  • Skilled nursing facility care
  • Inpatient hospital services
  • Home healthcare services

If prior authorization is necessary for any of these services, the process is very straight forward. Your provider will typically initiate the process by submitting the proper forms to Medicare. Your provider will outline your treatment and the reasoning for the specific services.

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From there, Medicare can determine whether your care will be covered.

Medicare Part B Prior Authorization

As part of Original Medicare, you’ll rarely need to obtain prior authorization for Medicare Part B services. However, in some circumstances, you may need to receive approval before receiving care. Medicare Part B covers the administration of certain drugs when given in an outpatient setting.

Some meds you receive may require your doctor to submit a Part B Drug Prior Authorization Request Form. Your doctor will provide and complete this form with detailed information regarding why the medication is necessary for your diagnosis. Once the request gets approval, you can begin receiving the medication.

Medicare Part D Prior Authorization

Often, even top Part D prescription drug plans need prior authorization for coverage on specific drugs. Different policies have varying rules, so you’ll need to contact the carrier directly to confirm coverage.

Most Part D plans have forms you can download online. The online option is a useful way to print the documents and take them to your doctor. Your doctor can help you correctly complete the form.

Also, recipients may directly contact their Part D plan and ask for a mail-in form. You can find the number for Member Services on your plan’s member ID card.

Medicare Advantage Prior Authorization

To obtain out-of-network, specialist, and emergency care, Medicare Advantage recipients may need prior authorization. Unfortunately, if Medicare doesn’t approve the request, the Advantage plan typically doesn’t cover any costs, leaving the full cost up to you.

In 2021, over 35 million Prior Authorization requests were submitted on behalf of Medicare Advantage plans. The services most often requiring prior approval are durable medical equipment, skilled nursing facility stays, and Part B drugs.

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However, each Medicare Advantage plan is different. If you are enrolled in a Medicare Advantage plan, contact your plan provider to determine if or when prior authorization is necessary. Your plan provider should also have forms you can download online outlining your covered services.

How Do I Get Prior Authorization for Medicare?

Refer to your plan documents, including the drug formulary, to see if your treatment requires approval. This information should be on your plan’s website. The Medicare & You handbook also contains more information.

Your provider is responsible for requesting permissions. Be sure to give them all the information they need for submission, ensuring it’s correct. Double-check your plan’s terms as well.

If your provider believes your treatment is medically necessary, they can contact your plan and request an exception if you get denied. The provider must support the request with a statement. Once approved, your plan pays without prior authorization.

How Long Does it Take to Get Prior Authorization?

The amount of time it takes to receive a verdict on your prior authorization request can vary based on each individual situation. It can take anywhere from a few days to a few weeks to receive a prior authorization from Medicare.

For a speedy prior authorization, it is important that your doctor provide detailed information regarding why the treatment is necessary to your specific case. Providing as much detailed information as possible will ensure the reviewer has all the information necessary to approve your case.

Missing information, diagnosis codes, or reasoning may delay your authorization and could even result in a denial.

Medicare Prior Authorization FAQs

Does Medicare require prior authorization for MRI?

If the purpose of the MRI is to treat a medical issue, and all providers involved accept Medicare assignment, Part B would cover the inpatient procedure. An Advantage beneficiary might need prior authorization to visit a specialist such as a radiologist.

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Does Medicare require prior authorization for a CT scan?

If your CT scan is medically necessary and the provider(s) accept(s) Medicare assignment, Part B will cover it. Again, you might need prior authorization to see an out-of-network doctor if you have an Advantage plan.

How do I get Medicare prior authorizations for a therapy regimen?

You’ll get prior authorization the same way, no matter the service. Your doctor will document medical necessity and send forms to either Medicare or your plan for approval.

Getting Help Understanding Prior Authorization

This information can seem overwhelming, and things are always changing. Our goal is to keep you informed to help you pick the best coverage for you. We can start helping by comparing rates in your area.

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Jagger Esch

Jagger Esch

Medicare Educator
Jagger Esch is the Medicare Educator for MedicareFAQ and the founder, president, and CEO of Elite Insurance Partners and MedicareFAQ.com. Since the inception of his first company in 2012, he has been dedicated to helping those eligible for Medicare by providing them with resources to educate themselves on all their Medicare options. He is featured in many publications as well as writes regularly for other expert columns regarding Medicare.
Ashlee Zareczny

Ashlee Zareczny

Compliance Manager
Ashlee Zareczny is the Compliance Manager for MedicareFAQ. As a licensed Medicare agent in all 50 states, she is dedicated to educating those eligible for Medicare by providing the necessary resources and tools. Additionally, Ashlee trains new and tenured Medicare agents on CMS compliance guidelines. Ashlee is a Medicare expert who specializes in Medicare Supplement, Medicare Advantage, and Medicare Part D education.

30 thoughts on "Medicare Prior Authorization Explained"

  1. I will need an arthroscopic surgery, out patient, for a meniscus tear in my right knee. Is Pre Authorization needed for this surgery, or does the doctor call it in.

    1. This will actually depend on the type of coverage you have. Typically if you are enrolled in a Medicare Advantage plan, you’ll need to go through prior authorization. However, some plans do not require PA before the surgery is covered. You’ll need to call your insurance company directly for a more specific answer.

  2. I am 84 and have had Medicare A & B since I’m 65, but I never signed up for Part D. If I switch to Medicare Advantage plan, can I get Par D?

    1. You can either enroll in a stand alone Medicare Part D plan or if you wish to enroll in a Medicare Advantage Prescription Drug Plan, you can do that as well. However, if you switch to Medicare Advantage, it is important to ensure your doctors and hospitals will be covered by the plan.

  3. I’m looking to see if Medicare needs a prior authorization for a patient to have Bariatric Surgery. Do I need to submit all required documentation a head of scheduling surgery? Is there a pre-determination required? Please advise. Thank you.

    1. Hello Gina, Medicare does require a prior authorization for bariatric surgery. You will need to submit your documentation ahead of the surgery.

  4. Hello. I have original Medicare with a medigap supplement. My primary care physician had me do an ultrasound examination of my heart with no issues found. Now, only 2 months later, my cardiologist wants me to have the same procedure performed. Will my original Medicare pay for this again?

    1. Joe, as long as the new ultrasound is deemed medically necessary, there should not be an issue with Medicare paying the claim. However, I would reach out to your physician as well to verify the coverage.

  5. hello Jagger, I was diagnosed with esophgeal cancer dec 15th 2021 during a routine upper GI scope.( I have GERD) I turned 65 years old last july and got set up on medicare with A&B and a AARP united health supplement plan and wellcare prescription plan last year. The cancer was first noted as very small but after going to more CT scans, PET scans and a endoscopic procedure in which it was determined the tumor was too large to remove. Now I am looking at chemo and radiation therapy followed by surgery to remove part of stomach and esophagus. being new to medicare and having this now become much more serious can you give me any advise on what to do to make sure I am getting all of the benefits I am entitles to.

    1. Hi Mark, I am sorry to hear about your diagnosis. After reading your comment it seems to me that you are enrolled in all the right plans and are receiving the benefits you are entitled to.

    1. Kady, Original Medicare typically does not need prior authorization if the sleep study has been deemed medically necessary by your doctor.

  6. Good morning. I have medicate and supplemental (Anthem) insurance. I have a routine colonscopy scheduled this week. Is pre-authorization from medicare required ? Does the doctor’s office or the patient contact medicare for pre-authorization ?

    1. Hi Irene – Part B will cover your CT scan if it is medically necessary, so you wouldn’t need prior authorization. If you have an Advantage plan, you may need prior authorization to visit a doctor outside of your network.


    1. Hi Joyce! If you have Original Medicare Part A & Part B only, no. If you have a Medicare Advantage plan, it’s up to the carrier if they require prior authorization.

  8. We just received a bill for $160,000 for a one-day procedure that was pre-authorized. Our insurance company says that Medicare won’t pay it, so the whole bill is on us even though we got pre-authorization. What is the use of pre-authorization if the bill isn’t going to be at least partially paid by Medicare?

    1. Hi Virginia. This sounds like a billing error. Your best option is to do a three-way call between the billing department and Medicare to have this resolved ASAP.

  9. My husband had an AVM 20 years ago. Ten years later a large cyst developed at site which required surgery. He has had small non-verbal seizures since then until 2 weeks ago. The last 2 caused confusion for an hour. It has been 11 days since doctor ordered MRI but we are waiting on prior authorization. Should it take that long?

    1. Hi Marilyn! Unfortunately, this is one of the many downfalls of Medicare Advantage plans. You should be able to log into your online portal either through the Advantage carrier or Medicare to see the status of your prior authorization. But yes, it can take this long depending on the carrier you enrolled with.

  10. I am inquiring if medicare is primary and patient has medicare supp as secondary and it follows medicare guidelines, is the medicare authorization used for the supplement coverage too or does a separate auth have to be obtained?

    1. Hi Maria! A Medicare Supplement policy will always cover anything Medicare overs. If Medicare approved the service or procedure and required a prior authorization form, the Medigap plan will NOT require an additional prior authorization form. I hope this helps!

  11. Lindsay I work in the health care field and come across unique situations. Can I reach out to you via email for questions?


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