GLP-1 Letter of Medical Necessity: What to Include (+ Template)

If your plan requires prior authorization for Wegovy or Zepbound, or it has already said no, the most important document in the file is usually the prescriber's letter of medical necessity (LMN). It turns a chart full of numbers into one clear argument that the plan's reviewer can check against their criteria.

Many of these letters are weak. They say the patient "has struggled with weight for years" and "would benefit from" the drug. That is not what a reviewer is checking. They have a written policy with specific boxes to tick, and a good letter ticks each one with a date, a measurement or a code.

This guide covers what insurers look for, what belongs in the letter, the mistakes that lead to denials, and a fill-in-the-blanks template your prescriber can adapt. It is general information to discuss with your prescriber, not medical advice. Only the prescriber can decide whether the drug is right for you and sign the letter.

What a letter of medical necessity is (and when you need one)

A letter of medical necessity is a signed statement from the prescriber explaining why a particular treatment is medically necessary for a particular patient. Novo Nordisk's sample Wegovy letter describes its purpose as explaining "the prescribing healthcare provider's rationale and clinical decision-making" to the insurer. It notes the letter can be used with a prior authorization or when Wegovy is not on the patient's formulary. Eli Lilly's Zepbound guide says the same and adds appeals of a coverage decision.

In practice, an LMN comes up in four situations:

1. Initial prior authorization (PA). Many plans accept the PA form alone. A letter helps when the case is borderline or the form has no room for the detail.
2. Formulary exception. The drug is not on your plan's list, or the plan prefers another GLP-1. The letter explains why the plan's preferred option is not appropriate.
3. Appeal after a denial. The letter is rewritten to answer the specific reason given in the denial.
4. Reauthorization. Approvals are time-limited. Continuing therapy usually means showing a response to treatment (see below).

Lilly's guide also notes that some plans require their own coverage authorization form instead of, or as well as, a free-text letter. Check what your plan wants before your prescriber starts writing.

If the plan excludes weight-loss drugs altogether, a letter alone rarely changes that. See our GLP-1 insurance coverage guide for how exclusions work and which indications fall outside them.

Start with the plan's written criteria

The biggest improvement you can make to any LMN is to get the insurer's actual coverage policy for the drug and write to it. Most large insurers and pharmacy benefit managers publish these as PDFs, and the plan's member services or the prescriber's office can request them. Criteria vary a lot between plans, and sometimes between different products from the same insurer.

Here are two real 2026 policies:

• UnitedHealthcare commercial (plans that cover weight-loss drugs), effective September 1, 2026. Wegovy (injection, tablet and HD) and Zepbound require use as an adjunct to lifestyle modification and a BMI of 30 or more, or 27 or more with a weight-related comorbidity (examples given: dyslipidemia, hypertension, type 2 diabetes, sleep apnea). Initial approval is 5 months for Wegovy products and 6 months for Zepbound. Reauthorization requires at least 5% loss of baseline body weight and continued lifestyle modification. The same document has a separate North Dakota fully insured EHB section requiring a BMI of 40 or more.
• Neighborhood Health Plan of Rhode Island, effective January 2026 (the Medicaid portion of a Medicare plan). This policy requires documented, current participation in a comprehensive weight-management program with behavioral counseling, nutrition counseling and exercise components, meeting at least monthly for 6 months before drug therapy. It also requires prescribing by or with a weight-loss clinic or dietitian. For Zepbound, it requires an inadequate response, intolerance or contraindication to Wegovy first.

That second example is why a generic letter fails. A letter that never mentions a monthly program or a Wegovy trial would be denied under that policy, however strong the rest of the case is.

What insurers look for, item by item

1. A diagnosis that matches the FDA-approved indication

Insurers check the request against the FDA label. As of the current labels (Wegovy revised 03/2026, Zepbound revised 02/2026):

The indication the letter names changes the case. A patient with a prior heart attack and a BMI of 28 may fit Wegovy's cardiovascular indication. A patient with moderate-to-severe OSA and obesity may fit Zepbound's OSA indication. Some plans cover these indications even where they exclude drugs "for weight loss." UnitedHealthcare, for example, has a separate Zepbound policy "for obesity with obstructive sleep apnea" for plans where weight-loss drugs are excluded.

2. BMI and weight, measured and dated

The current labels say "obesity" and "overweight" rather than giving BMI cutoffs in the indication. The weight-management trials described in both labels enrolled adults with a BMI of 30 or more, or 27 to under 30 with at least one weight-related condition, and most commercial policies use those same numbers. Wegovy's cardiovascular trial enrolled adults 45 and older with a BMI of 27 or more and established cardiovascular disease (prior heart attack, stroke or peripheral arterial disease). Zepbound's OSA trials enrolled adults with a BMI of 30 or more.

The letter should give a recent, clinic-measured height, weight and BMI with the date, plus the weight history if it helps. Some plans want a baseline weight on record so they can later measure the 5% response at reauthorization.

3. ICD-10 codes

Codes let the reviewer match the letter to the policy quickly. Codes the prescriber commonly uses include:

The CDC's guidance on the class codes tells providers to use E66.811–E66.813 together with the matching Z68 BMI code, and to move away from older codes such as E66.01 and E66.09. The exact code for each condition is the prescriber's call and must match the chart. Many conditions have more specific codes than the examples above.

4. Weight-related comorbidities, with evidence

If the case relies on "overweight plus a comorbidity," the comorbidity must be documented, not just listed. Include the relevant blood pressure readings, lipid panel, HbA1c or fasting glucose, sleep study results, or cardiac history, with dates. Lilly's guide specifically suggests calling out comorbid conditions "(i.e. obstructive sleep apnea)."

5. A documented lifestyle program

Both drugs are approved as an adjunct to diet and physical activity, and plans often ask for proof of a structured effort. Both manufacturers' templates include a lifestyle section. Novo's asks for each intervention with start date, end date and outcome, and Lilly's asks for "reduced calorie diet, increased physical activity, or lifestyle modification programs." As shown above, some plans set a minimum, such as monthly sessions for 6 months. List programs by name with dates, and attach records if you have them (program enrollment, dietitian notes, app exports).

6. Prior medications and step therapy

Novo's template includes a table for each previous drug with dose, start date, end date and reason for stopping or contraindication. If the plan requires a trial of a cheaper drug or a preferred GLP-1 first, the letter should show that trial happened, or explain why it can't. See our step therapy guide for how these requirements usually work.

7. Contraindications to the plan's alternatives

If the plan wants you to try an older weight-loss drug first, a documented contraindication is often the strongest reason to skip that step. Examples from the current FDA labels:

• Phentermine: history of cardiovascular disease (such as coronary artery disease, stroke, arrhythmias, heart failure or uncontrolled hypertension), hyperthyroidism, glaucoma, agitated states, history of drug abuse, pregnancy, nursing, or MAOI use within 14 days.
• Phentermine/topiramate (Qsymia): pregnancy, glaucoma, hyperthyroidism, or MAOI use within 14 days.
• Naltrexone/bupropion (Contrave): uncontrolled hypertension, seizure disorder or history of seizures, bulimia or anorexia nervosa, chronic opioid use, other bupropion products, or MAOI use.
• Orlistat (Xenical): pregnancy, chronic malabsorption syndrome, or cholestasis.

A patient with a prior stroke, for example, may not be a candidate for phentermine under its label. The letter should say so and cite the label. The prescriber should also confirm the patient has no contraindication to the drug being requested. Wegovy and Zepbound are both contraindicated in patients with a personal or family history of medullary thyroid carcinoma or MEN 2, and in patients with prior serious hypersensitivity to the drug. See who shouldn't take a GLP-1.

8. For Zepbound and sleep apnea: the sleep study and PAP history

For the OSA indication, the evidence is different. UnitedHealthcare's Zepbound OSA-only policy (effective September 1, 2026) requires medical records showing:

• BMI of 30 or more
• Moderate-to-severe OSA on a sleep study, with an AHI, REI or RDI of at least 15 events per hour
• At least one previous unsuccessful dietary effort to lose weight
• Either continued OSA symptoms despite adherent PAP use (defined as 4 or more hours a night on at least 70% of nights), or a reason the patient is not a candidate for PAP
• No diagnosis of diabetes and no HbA1c above 6.5%
• Prescriber attestation about positional therapy counseling, alcohol and sedative counseling, no planned sleep or obesity surgery, and no predominantly central or mixed sleep apnea
• Prescribing by or with a sleep specialist, pulmonologist, otolaryngologist, or a physician experienced in OSA

Other plans will differ, but this shows the level of detail a sleep apnea letter may need. Attach the sleep study report and PAP download data if you have them. More background is in our GLP-1s and sleep apnea guide.

Fill-in-the-blanks template letter

The template below follows the structure of the manufacturers' published sample letters. It is a template only. Every bracketed field must be completed by the prescriber from the patient's medical record, checked against the plan's written criteria, and signed by the prescriber. Delete any section that does not apply. Do not submit it unedited.

Common mistakes that lead to denials

Writing to the drug instead of to the policy. The reviewer is checking a list. If the plan requires monthly program visits for six months, a letter that says "tried diet and exercise" does not meet it.

Using self-reported or old weights. Give a clinic-measured weight and BMI with a date. Some plans compare against this baseline later for reauthorization.

Missing or mismatched codes. A letter that says "class 2 obesity" but codes E66.9 with no Z68 code makes the reviewer work harder. Use the class code with the matching BMI code, as the CDC advises.

Undated history. "Has tried phentermine" is weak. "Phentermine 37.5 mg daily, [date] to [date], stopped because of [reason]" matches what the manufacturers' templates ask for.

Naming the wrong indication. If the strongest case is cardiovascular risk reduction (Wegovy) or sleep apnea (Zepbound), say so. It can put the request under a different policy.

Ignoring the plan's preferred drug. If the plan prefers one GLP-1, the letter for the other needs a documented reason: an inadequate response, intolerance or a contraindication.

Not answering the denial reason on appeal. An appeal letter should quote the denial reason and answer it. Lilly's sample appeal letter starts this way: "the reason for your denial is [copy reason verbatim from the plan's denial letter]."

Leaving out attachments. The letter summarizes, and the records prove it. List every enclosure.

Forgetting the signature, NPI or contact details. Both manufacturers' templates include the prescriber's NPI and contact information. An unsigned letter, or one with no phone number for a peer-to-peer call, slows everything down.

How the letter fits into prior authorization, exceptions and appeals

At the initial PA, the prescriber's office submits the plan's PA form (often electronically) with chart notes. A letter is optional for some plans and expected by others. Sending a strong letter the first time can prevent an avoidable denial.

For a formulary exception, federal rules for plans that must cover essential health benefits (such as Marketplace plans) require an exception process. The plan must decide a standard exception request within 72 hours and an expedited request, based on exigent circumstances, within 24 hours. If it denies the request, the enrollee or prescriber can ask for an independent review of that decision on the same timelines. The LMN is the core of that request.

After a denial, the letter gets rewritten to answer the denial reason and goes into the internal appeal, often with a peer-to-peer call between the prescriber and the plan's reviewer. If internal appeals fail, most plans allow an external review. Deadlines, timelines and step-by-step instructions are in our GLP-1 prior authorization appeal guide.

At reauthorization, the letter or form shows the response. Under the UnitedHealthcare policy above, that means at least 5% loss of baseline body weight plus continued lifestyle modification. Keep the baseline weight from the first letter so the comparison is easy.

Medicare patients have different rules for obesity drugs. See our Medicare GLP-1 coverage guide. Both manufacturers note that in a Medicare appeal, specific requirements must be met before a prescriber can act as the patient's legal representative. They point to CMS form 1696 (Appointment of Representative).

What you can do as the patient

Your prescriber writes and signs the letter, but you can make it much easier:

1. Get the plan's coverage policy for the specific drug and send it to your prescriber's office.
2. Build a dated timeline of every diet, program, app, dietitian visit and weight-loss medication you have tried, with approximate dates, doses and why you stopped.
3. Collect records: program enrollment confirmations, pharmacy history (your pharmacy can print this), and any sleep study or cardiology reports.
4. Send the denial letter word for word if you are appealing.
5. Ask directly whether the office will request a peer-to-peer review if the plan denies again.

If you would rather not manage this yourself, some telehealth services handle PA paperwork and appeals for you. See our insurance-friendly GLP-1 telehealth comparison. If coverage is delayed or denied, the manufacturers' direct self-pay programs are an alternative. See our walkthroughs for NovoCare Pharmacy (Wegovy) and LillyDirect (Zepbound).

Related coverage guides

• Zepbound prior authorization
• Wegovy prior authorization
• If your employer dropped GLP-1 coverage
• GLP-1 coverage by PBM (CVS Caremark, Express Scripts, Optum Rx)
• Ozempic and Mounjaro prior authorization for type 2 diabetes
• How to appeal a GLP-1 prior authorization denial
• Step therapy for Wegovy and Zepbound