Quick Answer
Prior authorization (PA) is required by Medicare Advantage and Part D plans before approving certain services or drugs. Original Medicare rarely requires PA. If denied, you have the right to appeal within 60 days.
Coverage Comparison by Plan Type
| Plan Type | Coverage | Notes |
|---|---|---|
| Original Medicare | Rarely Required | PA required for only a few services (e.g., some home health) |
| Medicare Advantage | Commonly Required | Plans set their own PA requirements for specialists, surgeries, imaging |
| Part D | For Some Drugs | Required for certain high-cost or specialty drugs on formulary |
| Medigap | Not Applicable | Medigap supplements Original Medicare; PA rules follow Original Medicare |
Understanding Your Coverage Options
Original Medicare (Part a & B)
Original Medicare does not require prior authorization for most services. Your doctor can generally order tests, referrals, and procedures without advance approval from Medicare.
A small number of services - such as certain home health agency services and some outpatient therapy - may require documentation of medical necessity, but this is not the same as a formal prior authorization process.
What It Covers
- Most Part B services without advance approval
- Hospital admissions (Part A) without pre-approval
- Physician referrals without PA requirement
What It Doesn't Cover
- Formal PA process does not apply to most Original Medicare services
- Some home health services require medical necessity documentation
Medicare Advantage (Part C)
Medicare Advantage plans are required to cover everything Original Medicare covers, but they can impose prior authorization requirements for many services. Common PA requirements include specialist visits, inpatient hospital stays, skilled nursing facility care, imaging (MRI, CT scans), and certain surgeries.
The CMS 2024 Prior Authorization Rule requires MA plans to make PA decisions within 72 hours for urgent requests and 7 calendar days for standard requests. Plans must also provide a specific reason for any denial.
What It Covers
- Specialist referrals (with PA approval)
- Inpatient hospital stays (with PA approval)
- Imaging and diagnostic tests (with PA approval)
- Surgeries and procedures (with PA approval)
What It Doesn't Cover
- Emergency services - PA cannot be required for emergencies
- Urgently needed care while temporarily outside the plan area
Medicare Part D
Part D plans use prior authorization for certain drugs on their formulary - typically high-cost, specialty, or brand-name medications. Your doctor must submit clinical documentation showing the drug is medically necessary for your condition.
Step therapy is a related requirement where you must try a lower-cost drug first before the plan will approve a more expensive alternative. If the first-line drug fails or is contraindicated, your doctor can request a PA exception.
What It Covers
- Formulary drugs after PA approval
- Specialty drugs with documented medical necessity
- Step therapy exceptions when lower-cost drugs fail
What It Doesn't Cover
- Off-formulary drugs (require a formulary exception, not just PA)
- Drugs not covered by Part D (e.g., weight loss drugs, vitamins)
How to Request Prior Authorization
Your doctor or specialist typically submits the PA request on your behalf. They will provide clinical notes, diagnosis codes, and supporting documentation to your plan. You can also call your plan's member services line to check the status of a pending PA.
If your PA is denied, you have the right to appeal. For Medicare Advantage, you can request a reconsideration from the plan, and then escalate to an Independent Review Entity (IRE) if still denied. Time limits apply: standard appeals must be filed within 60 days of the denial notice.
What It Covers
- Doctor-submitted PA requests on your behalf
- Expedited PA for urgent medical situations (72-hour decision)
- Right to appeal any PA denial within 60 days
What It Doesn't Cover
- Retroactive PA for services already received (generally not allowed)
- PA approval does not guarantee payment if other coverage rules apply
Prior Authorization at a Glance
| Plan Type | PA Required? | Decision Timeline | Appeal Right | Emergency Exception |
|---|---|---|---|---|
| Original Medicare | Rarely | N/A | Yes | Yes |
| Medicare Advantage | Yes - many services | 72 hrs (urgent) / 7 days (standard) | Yes - 60 days | Yes - always exempt |
| Part D | Yes - some drugs | 24 hrs (urgent) / 72 hrs (standard) | Yes | Emergency supply rules apply |
| Medigap | No | N/A | N/A | N/A |
✦ Important Exceptions and Protections
Emergency Care is Always Exempt
Medicare Advantage plans cannot require prior authorization for emergency medical care. If you have a medical emergency, go to the nearest emergency room - your plan must cover it regardless of PA status.
Emergency services are always covered without prior authorization under both Original Medicare and Medicare Advantage.
2024 CMS Prior Authorization Rule
CMS issued a final rule in 2024 requiring Medicare Advantage plans to streamline PA processes, provide specific denial reasons, and implement electronic PA systems by 2026. Plans must also honor PA approvals for the duration of a course of treatment.
MA plans must now provide a specific clinical reason for every PA denial - vague denials are no longer permitted.
Continuity of Care Protections
If you switch Medicare Advantage plans mid-year, your new plan must honor prior authorizations from your old plan for up to 90 days to ensure continuity of care.
You have 90 days of continuity of care protection when switching MA plans.
✦ Legislative Update
CMS 2024 Prior Authorization Rule
PassedCMS finalized rules requiring Medicare Advantage plans to implement electronic prior authorization, provide specific denial reasons, and meet stricter decision timelines. Electronic PA systems required by January 1, 2026.
GOLD Card Act
ProposedWould exempt physicians who have a track record of PA approvals from having to request PA for Medicare Advantage patients. Introduced in multiple sessions of Congress but not yet passed.
Improving Seniors' Timely Access to Care Act
PassedSigned into law in 2022, this act codified many of the electronic PA and transparency requirements for Medicare Advantage plans.
What to do if Prior Authorization is Denied
A PA denial is not the end of the road. You have clear rights under Medicare to appeal any coverage decision.
Work with your doctor to submit a strong appeal with clinical documentation. Many PA denials are overturned on appeal, especially when supported by medical records and a physician's letter of medical necessity.
PA Denial Action Steps
- Request the specific reason for the denial in writing
- Ask your doctor to submit a letter of medical necessity
- File a formal appeal within 60 days of the denial
- Request an expedited appeal if your health is at risk (72-hour decision)
- Escalate to an Independent Review Entity (IRE) if plan upholds denial
- Contact your State Health Insurance Assistance Program (SHIP) for free help
- File a complaint with CMS if the plan violates PA rules
✦ Frequently Asked Questions
David Haass
AuthorDavid Haass is a licensed Medicare expert who has been helping beneficiaries navigate their Medicare options for over a decade.
Ashlee Zareczny
ReviewerAshlee Zareczny is a licensed Medicare agent dedicated to helping those eligible for Medicare find the best coverage options.