Medicare Advantage Prior Auth: What Makes It Different from Traditional Medicare

Here's something that trips up practices constantly: a patient turns 65, moves to Medicare, and suddenly a biologic that sailed through approvals for years hits a wall. Not because the drug changed. Not because the diagnosis changed. Because which Medicare matters enormously — and traditional Medicare and Medicare Advantage operate under completely different prior authorization rules.

If your practice sees patients with MA plans, this distinction is worth understanding cold.

Traditional Medicare: Coverage by Coverage Determination

Traditional Medicare — fee-for-service Medicare, sometimes called Original Medicare — doesn't operate with a prior authorization system the way commercial payers do. Coverage is determined by Local Coverage Determinations (LCDs) and National Coverage Determinations (NCDs) published by CMS and Medicare Administrative Contractors.

These are public documents. Your biller can look up exactly what documentation CMS requires for a given biologic and diagnosis code. If your documentation meets the criteria, the claim pays. There's no prior authorization step in the middle — no submission, no waiting period, no plan-specific approval queue.

This doesn't mean traditional Medicare is frictionless. You still need to document medical necessity, meet the LCD criteria, and get the coding right. But you're working against published, stable standards — not a black box of payer-specific requirements.

Medicare Advantage: Prior Auth Layered on Top

Medicare Advantage plans are administered by private insurers — UnitedHealthcare, Humana, Aetna, BCBS affiliates — who contract with CMS to provide Medicare benefits. They're required to cover everything traditional Medicare covers, but they're allowed to use utilization management tools, including prior authorization, to manage that coverage.

That's where the friction comes in. An MA plan can require prior authorization for a biologic even when traditional Medicare would pay the same claim without one. The plan can also set its own documentation standards, step therapy requirements, and formulary preferences — all on top of the baseline Medicare coverage rules.

In practice, this means a patient on a UnitedHealthcare MA plan and a patient on traditional Medicare may have the same diagnosis and the same prescription, but the prior authorization burden is completely different. The MA patient requires an approval. The traditional Medicare patient doesn't.

The Scale of the Problem

Medicare Advantage enrollment has grown steadily for years. As of 2024, more than 54% of Medicare enrollees were in MA plans — about 33 million people. That number continues to climb.

For practices with older patient populations — rheumatology, oncology, dermatology — the majority of Medicare patients are now in MA plans. That means the majority of Medicare PA submissions are going to private insurers, not to traditional Medicare, where the LCD framework makes coverage predictable.

The OIG has documented what this looks like at scale. A 2022 report found that MA plans denied 13% of prior authorization requests that met Medicare coverage rules — meaning plans were denying care that would have been covered under traditional Medicare. That's not a small rounding error. At the volume of biologics PAs in a typical specialty practice, those denial rates translate directly into delayed patient care and staff time spent on appeals.

How MA Prior Auth Requirements Differ from Commercial

If you're used to commercial payer PA requirements, MA requirements feel similar — but there are meaningful structural differences.

Commercial payer requirements vary by employer group, plan tier, and benefit design. MA requirements are theoretically constrained by what Medicare would cover, but plans have significant latitude in how they operationalize that. An MA plan can require step therapy before approving a biologic even when CMS's own step therapy rules are more limited. CMS issued guidance in 2018 specifically allowing MA step therapy for Part B drugs, which opened the door for plans to layer additional requirements onto an already complex system.

MA plans also tend to shift their formularies and PA criteria annually — sometimes mid-year for biosimilar additions. A biologic that was preferred last year may require extra documentation steps this year. Commercial plans do this too, but the MA context adds a wrinkle: patients often don't realize they're in a plan with different rules than what they think of as "regular Medicare."

CMS Oversight and Recent Crackdowns

CMS has been tightening oversight of MA prior authorization practices. The 2024 final rule included provisions requiring MA plans to make PA decisions faster, use clinical criteria aligned with traditional Medicare coverage, and provide more detailed denial explanations.

The 2024 Medicare Advantage final rule specifically requires MA plans to use "current evidence-based criteria" when making PA decisions for Part B drugs — a direct response to the OIG's findings about inappropriate denials. Plans that deviate from Medicare coverage standards now face more scrutiny.

This doesn't eliminate MA prior auth. It raises the floor. Plans still require prior authorization; they're just under more pressure to apply it consistently with Medicare coverage rules. For providers, that means two things: the criteria are becoming more predictable, and well-documented submissions that clearly meet Medicare standards have a stronger path to approval.

Documentation Strategies Specific to MA

The most effective MA PA strategy mirrors the same principle that works in traditional Medicare: document to the LCD/NCD standard first, then address the plan's additional requirements.

Start by identifying which Medicare Administrative Contractor jurisdiction covers your patient. The relevant LCD tells you exactly what CMS expects for medical necessity. Document to that standard completely — diagnosis codes, disease severity, duration of condition, failed treatments, lab values if required. Then layer in whatever the MA plan specifically requires on top: their step therapy documentation, their preferred formulary history, their specific form fields.

Appeals in the MA context are also worth understanding. MA plans must follow Medicare's appeals process, which includes fast-track appeals (72 hours for urgent cases) and standard appeals. The OIG findings on inappropriate denials suggest that well-constructed appeals citing Medicare coverage criteria have a reasonable success rate — plans are aware of the scrutiny they're under.

Luma researches MA-specific payer criteria alongside standard Medicare LCD/NCD documentation requirements. When a submission is going to a UnitedHealthcare or Humana MA plan, the generated documentation accounts for both the Medicare coverage standard and the plan's specific requirements — so nothing gets left out of the submission.

For more on how payer-specific research affects documentation quality, see related posts on the Luma blog.

The Bottom Line

Traditional Medicare and Medicare Advantage are not the same thing when it comes to prior authorization. One uses LCD/NCD criteria with no PA step. The other layers private insurer requirements on top of Medicare coverage rules — requirements that can and do result in denials that wouldn't happen under traditional Medicare.

With MA enrollment now above 54% of Medicare beneficiaries, most specialty practices are already majority-MA for their Medicare population. Treating those patients the same as traditional Medicare patients — from a documentation standpoint — is a fast path to denials that could have been avoided.

The fix isn't complicated: know which plan you're dealing with, document to Medicare standards first, and address the plan's specific requirements on top. That's the structure that survives MA scrutiny.

Sources: CMS Medicare Coverage Database, Local Coverage Determinations and National Coverage Determinations (cms.gov/medicare-coverage-database); Kaiser Family Foundation, "Medicare Advantage in 2024: Enrollment Update and Key Trends" (kff.org); OIG Report OEI-09-18-00260, "Medicare Advantage Prior Authorization: Program Integrity Risks" (oig.hhs.gov); CMS, "Medicare Advantage Step Therapy for Part B Drugs" fact sheet (cms.gov); CMS, 2024 Medicare Advantage and Part D Final Rule press release (cms.gov).