Prior authorization — the requirement for Medicare to approve certain equipment before it's delivered — affects millions of Medicare beneficiaries every year. When it works smoothly, it's barely noticeable. When it doesn't, it can delay critical equipment by weeks and generate confusing denial letters. This guide explains the process from start to finish, so you know what to expect and what to do if things go wrong.

What Is Prior Authorization?

Prior authorization (PA) is a process in which a Medicare-enrolled supplier requests approval from Medicare — through a Medicare Administrative Contractor (MAC) — before delivering specific equipment. Medicare reviews clinical documentation submitted by the supplier and the prescribing physician and issues a decision: approved, approved with modifications, or denied.

The purpose of PA is to confirm that:

  • The patient's diagnosis and clinical condition meet Medicare's coverage criteria
  • The specific equipment is medically necessary and appropriate
  • Documentation is in order before Medicare commits to payment

PA is not a guarantee of payment — even if a PA request is approved, the claim can still be denied later if the documentation on the actual claim doesn't match what was approved. But PA approval significantly reduces the risk of denial.

Which Equipment Requires Prior Authorization?

CMS has expanded the PA program significantly over the past several years. As of 2026, prior authorization is required for the following equipment categories (note: requirements apply in all states for certain items, and in specific states for others):

Nationwide PA Requirements

  • Power mobility devices — power wheelchairs and scooters (all groups)
  • Non-invasive ventilators — including CPAP and BiPAP for new beneficiaries in select markets
  • Enteral nutrition equipment — feeding pumps in high-fraud areas
  • Transcutaneous electrical nerve stimulation (TENS) units
  • Customized prosthetics and orthotics — above a certain cost threshold

Items Added in 2025–2026

  • Group 3 and higher power wheelchairs — expanded from complex rehab only
  • Home infusion therapy pumps — in designated high-utilization areas
  • Negative pressure wound therapy (NPWT) — portable devices

This list evolves. Always confirm current PA requirements with your supplier before ordering, as new equipment categories are added regularly.

Check PA requirements by equipment type in our Coverage Hub →

How the Prior Authorization Process Works

The PA process has several steps, and most of it happens between your supplier and Medicare — not directly with you. However, your physician's office plays a critical role.

Step 1: Physician Documentation

Your prescribing doctor must provide:

  • A written order for the specific equipment
  • A detailed written order (DWO) that includes patient diagnosis, clinical findings, and how the equipment addresses the medical need
  • Recent supporting clinical records (face-to-face examination notes, diagnostic test results)
  • For power wheelchairs: a face-to-face examination conducted within the past 6 months, plus a mobility-related activities of daily living (MRADL) assessment

Step 2: Supplier Submits the PA Request

Your supplier compiles the documentation and submits the PA request to the relevant Medicare Administrative Contractor (MAC). Requests are submitted electronically in most cases.

The MAC has 10 business days to respond to an initial PA request for non-urgent equipment, and 2 business days for urgent situations (when the patient's health requires immediate delivery).

Step 3: MAC Reviews and Decides

The MAC reviews whether the documentation supports coverage under Medicare's Local Coverage Determination (LCD) or National Coverage Determination (NCD) for that equipment type. They will issue one of three decisions:

  • Affirmed (approved) — the PA is granted; the supplier can deliver and bill
  • Non-affirmed (denied) — Medicare won't cover the item based on submitted documentation; supplier cannot deliver and bill Medicare (though the patient could still pay out of pocket)
  • Incomplete — more documentation needed; the clock resets when additional information is submitted

Common Reasons Prior Authorization Is Denied

  • Physician's written order doesn't include all required elements (diagnosis code, equipment description, start date)
  • Clinical documentation doesn't demonstrate medical necessity per the LCD criteria
  • Face-to-face examination was conducted too long ago (for power mobility, must be within 6 months)
  • The patient doesn't have the required diagnosis (e.g., COPD for oxygen, AHI ≥ 5 for CPAP)
  • The supplier submitted the wrong HCPCS code for the equipment
  • Documentation describes functional ability that doesn't meet the medical necessity threshold

How to Appeal a Prior Authorization Denial

If the MAC issues a non-affirmation, you and your supplier have the right to appeal. The appeal process for PA differs slightly from the standard Medicare claim appeal process.

Reconsideration

Within 30 calendar days of a non-affirmation, the supplier can submit a reconsideration request with additional documentation. This goes back to the same MAC. The MAC has 10 business days to respond to a reconsideration request.

What Strengthens an Appeal

  • Updated physician notes that explicitly address the coverage criteria that were cited as missing
  • Results of functional assessments (for mobility devices, a formal PT or OT evaluation)
  • Hospital records, diagnostic test results, or specialist notes that corroborate medical necessity
  • A letter of medical necessity from the treating physician explaining the clinical rationale in plain language

Tips for Navigating the PA Process

  1. Start early. PA requests take up to 2 weeks for routine equipment. If you know you'll need equipment at a specific time (hospital discharge, post-surgery), start the PA process well in advance.
  2. Choose a supplier experienced with PA. Suppliers who regularly handle power wheelchairs, ventilators, and other PA-required items have documentation workflows that reduce denials significantly.
  3. Keep copies of everything. Request copies of all submitted documentation. If you need to appeal, you'll want to know exactly what was submitted.
  4. Get your doctor involved early. Many PA denials happen because the physician's office sends incomplete records. Brief your doctor on what Medicare's LCD for your specific equipment requires.
  5. Track the timeline. Know when the PA was submitted and when the MAC's 10-day clock expires. If you haven't heard back, follow up with your supplier.

Frequently Asked Questions

Does prior authorization guarantee Medicare will pay my claim?

No. PA affirms that coverage criteria appear to be met based on submitted documentation. The actual claim can still be denied if the delivered equipment doesn't match what was approved, or if billing errors occur. However, an affirmed PA gives you strong grounds to appeal any subsequent denial.

Can I get equipment delivered while the PA request is pending?

Generally, no — suppliers risk not being paid if they deliver before PA is granted for required-PA equipment. In urgent situations (2-day expedited review), suppliers may deliver at risk and request emergency PA. Discuss this with your supplier.

Who handles the PA submission — me or my supplier?

Your supplier submits the PA request. Your physician must provide the supporting documentation. Your role is to make sure your doctor sends complete records promptly. Delays in physician documentation are the most common source of PA processing delays.

Explore coverage details and PA requirements for all DME categories →