Medicare health insurance helps pay for many medical services and prescriptions, but not everything is covered automatically. For certain drugs, tests, procedures, or equipment, Medicare requires something called prior authorization before they will pay their share. This step can feel confusing or frustrating, especially when you are waiting for treatment.
Prior authorization means your doctor or other provider must get approval from Medicare (or your Medicare Advantage plan) before the service or item is provided. The goal is to make sure the item is medically necessary and meets Medicare’s coverage rules. Without approval, you may have to pay the full cost yourself.
This article explains how prior authorization works under Medicare in 2025. It covers which services most often need it, the steps involved, what to do if coverage is denied, and practical ways to prepare so you avoid delays or unexpected bills. Rules can change, so always check with your plan for the latest details.
What Prior Authorization Means in Medicare
Prior authorization is a process where Medicare reviews a doctor’s recommendation before agreeing to pay for it. The doctor submits information showing why the service or drug is medically necessary. Medicare then decides whether it meets their coverage criteria.
If approved, Medicare pays its share according to your plan rules. If denied, the service is not covered unless you appeal successfully. You can still get the treatment, but you will pay the full cost out-of-pocket.
Prior authorization applies to both Original Medicare (Parts A and B) and Medicare Advantage plans (Part C). Medicare Part D (prescription drug plans) also uses prior authorization for many medications, especially expensive or specialty drugs.
Services and Drugs That Most Often Require Prior Authorization
Certain categories trigger prior authorization more than others. These include:
- High-cost specialty drugs (cancer treatments, biologics, some diabetes drugs)
- Certain durable medical equipment (power wheelchairs, hospital beds)
- Some outpatient procedures (MRIs, CT scans, PET scans in non-hospital settings)
- Home health services beyond short periods
- Infusion drugs given at home or in a clinic
For prescription drugs under Part D, common examples include GLP-1 medications (Ozempic, Wegovy, Mounjaro, Zepbound), some cancer drugs, hepatitis C treatments, and growth hormones. Each plan’s formulary lists exactly which drugs need prior authorization.
Medicare Advantage plans often have stricter rules than Original Medicare. They may require prior authorization for services Original Medicare covers without it.
How the Prior Authorization Process Works Step by Step
- Your doctor decides you need a service or drug that requires prior authorization.
- The doctor’s office (or the pharmacy for drugs) submits a request to Medicare or your Medicare Advantage plan.
- The request includes your medical records, diagnosis, and explanation of why the item is necessary.
- Medicare reviews the request (usually within 7–14 days for standard requests; 72 hours for urgent cases).
- You and your doctor receive a decision: approved, denied, or approved with modifications.
- If approved, the service or drug is covered according to your plan rules. If denied, you can appeal.
Appeals can go through several levels. The first level is a redetermination by the same plan. Higher levels involve independent reviewers or administrative law judges.
Comparison of Prior Authorization Timelines and Approval Rates (2025 Estimates)
| Plan Type | Standard Review Timeline | Urgent Review Timeline | Typical Approval Rate for Common Drugs | Most Frequent Denial Reasons |
|---|---|---|---|---|
| Original Medicare Part B | 14 days | 72 hours | 80–90% (when documentation complete) | Incomplete records |
| Medicare Part D | 14 days | 72 hours | 70–85% | Step therapy not met |
| Medicare Advantage (Part C) | 14 days | 72 hours | 60–80% | Not medically necessary |
Medicare Advantage plans tend to have lower approval rates and stricter criteria than Original Medicare. Complete documentation improves approval chances significantly.
Common Reasons for Denial and How to Avoid Them
Denials often happen because the request lacks required information. Common reasons include:
- Missing medical records showing why the drug or service is necessary
- Failure to show that less expensive alternatives were tried first (step therapy)
- No documented BMI or comorbidity for weight-loss drugs
- Incomplete forms or missing signatures
To reduce denial risk, work closely with your doctor’s office. Make sure they include:
- Your current diagnosis and relevant test results
- History of previous treatments and why they were not enough
- Specific clinical notes explaining medical necessity
- Any supporting letters from specialists
Appeals succeed in 30–50% of cases when stronger documentation is added. Keep copies of everything submitted.
Practical Tips to Prepare for Prior Authorization
Ask your doctor’s office early whether prior authorization is needed for your medication or procedure. Request they start the process as soon as possible—delays can add weeks to your wait time.
Gather your own records if needed: recent lab results, BMI calculation, list of previous treatments tried, and notes on symptoms or limitations caused by your condition. Share these with your provider to strengthen the request.
If denied, file an appeal quickly—deadlines are usually 60 days from the denial notice. Ask your doctor for a detailed letter of medical necessity explaining why the drug or service is essential for your health.
- Steps to Strengthen a Prior Authorization Request:
- Provide recent labs and test results
- Document failed previous treatments
- Include a clear explanation of medical necessity
- Attach specialist notes if applicable
- Submit the request as early as possible
What to Do When Prior Authorization Is Denied
First, read the denial letter carefully—it must explain the exact reason and your appeal rights. Ask your doctor’s office to help file the first-level appeal (redetermination) with additional documentation.
If the first appeal is denied, you can request reconsideration by an independent reviewer (second level). Higher levels involve administrative law judges or federal review. Many denials are overturned at the first or second level when more evidence is provided.
While appealing, you can still get the medication or service by paying out-of-pocket and requesting reimbursement if the appeal succeeds. Some providers will hold off collection until the appeal is resolved.
Alternatives When Coverage Is Denied
If prior authorization is repeatedly denied, explore manufacturer patient assistance programs. Novo Nordisk (for Ozempic/Wegovy) and Eli Lilly (for Mounjaro/Zepbound) offer free medication to qualifying uninsured or underinsured patients who meet income guidelines.
Compounded versions of semaglutide or tirzepatide are available through telehealth providers at $199–$499 per month. These are not covered by Medicare but are cash-pay options for patients denied branded coverage.
Other medications in the same class (e.g., dulaglutide/Trulicity) may have better coverage under some plans. Discuss alternatives with your doctor if Wegovy or Zepbound remains uncovered.
Conclusion
Medicare does not cover weight loss injections like Wegovy or Zepbound when used only for obesity, but Ozempic and Mounjaro are usually covered for type 2 diabetes with prior authorization. Limited pilot programs in 2025 test broader coverage in select areas. If denied, appeal with strong documentation, apply for manufacturer assistance, or explore compounded options. Work closely with your doctor to navigate rules and find the most affordable, safe path forward.
FAQ
Does Medicare cover Wegovy or Zepbound for weight loss?
No. Medicare Part D excludes coverage for drugs used only for weight loss or obesity under current federal law. Ozempic and Mounjaro are covered when prescribed for type 2 diabetes.
Are there any exceptions where Medicare covers weight loss injections?
Yes, if the injection treats a covered condition such as type 2 diabetes. Some limited pilot programs in 2025 test coverage for obesity in select regions, but these are not available nationwide.
What should I do if my Medicare plan denies coverage?
Appeal the denial with medical documentation showing medical necessity. Ask your doctor to submit additional records or a letter of medical necessity. If denied again, explore manufacturer patient assistance or compounded alternatives.
How much does Wegovy cost without Medicare coverage?
The cash price for a 4-week supply is typically $1,300–$1,400 at retail pharmacies in 2025. Discount cards can reduce it to $900–$1,100 per month at participating locations.
Can I get Wegovy free through a patient assistance program?
Yes. Novo Nordisk’s Patient Assistance Program provides free Wegovy to uninsured or underinsured patients who meet income guidelines (usually ≤400% of the federal poverty level). Approval requires financial documentation and takes 2–6 weeks.
Are compounded versions of GLP-1 drugs covered by Medicare?
No. Compounded semaglutide or tirzepatide is not covered by Medicare. These are cash-pay options ($199–$499/month through telehealth) for patients denied branded coverage. Quality varies, so choose reputable providers.
Dr. Usman is a medical content reviewer with 12+ years of experience in healthcare research and patient education. He specializes in evidence-based health information, medications, and chronic health topics. His work is based on trusted medical sources and current clinical guidelines to ensure accuracy, transparency, and reliability. Content reviewed by Dr. Usman is for educational purposes and does not replace professional medical advice.