What Is the Difference Between Mounjaro and Zepbound?

Why do Mounjaro and Zepbound have different names?

The brand name tracks the approved use, not a different molecule — each brand has its own FDA-approved indication and its own prescribing information. Mounjaro's initial U.S. approval year is 2022; its approval is for glycemic control, and chronic weight management is not an approved indication under the Mounjaro label. Zepbound's label carries the weight-reduction indication and the obstructive sleep apnea indication instead.

There is also no generic to fall back to. Lilly's state pricing disclosure for Mounjaro states there are no generic prescription drugs available from the same therapeutic class (USC 39259, anti-diabetic hormone, other), as of its January 2, 2025 disclosure sheet.

Are Mounjaro and Zepbound interchangeable?

No — chemically they are the same drug, but administratively they are not the same product, and the prescription names one of them. Coadministration of Zepbound with other tirzepatide-containing products or with any GLP-1 receptor agonist is not recommended, so a change of brand is a switch, not an addition — and a decision for your prescriber.

Both brands carry the same boxed warning: tirzepatide causes thyroid C-cell tumors in rats, and it is unknown whether Mounjaro or Zepbound causes thyroid C-cell tumors, including medullary thyroid carcinoma (MTC), in humans. Both are contraindicated in patients with a personal or family history of medullary thyroid carcinoma (MTC) or in patients with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2), per the Mounjaro and Zepbound prescribing information (Section 4, Contraindications) as of August 5, 2026.

The side-effect lists overlap heavily. Per each brand's prescribing information as of August 5, 2026, the most common adverse reactions reported in at least 5% of treated patients are: for Mounjaro — nausea, diarrhea, decreased appetite, vomiting, constipation, dyspepsia, and abdominal pain; for Zepbound — nausea, diarrhea, vomiting, constipation, abdominal pain, dyspepsia, injection site reactions, fatigue, hypersensitivity reactions, eructation, hair loss, and gastroesophageal reflux disease.

Reported rates come from different trials in different populations. Per the labels as of August 5, 2026: in Mounjaro's placebo-controlled trials, nausea was reported in 12% (5 mg), 15% (10 mg), and 18% (15 mg) of Mounjaro-treated patients versus 4% with placebo; in the Zepbound weight-reduction trials, nausea was reported by 25% of patients on 5 mg, 29% on 10 mg, and 28% on 15 mg, versus 8% on placebo. These are not head-to-head figures.

The efficacy data likewise come from different endpoints and populations. In SURPASS-2, a 40-week trial versus semaglutide 1 mg added to metformin published in 2021, HbA1c fell by 2.0% (5 mg), 2.2% (10 mg), and 2.3% (15 mg) with Mounjaro versus 1.9% with semaglutide. In SURMOUNT-1, published in 2022, mean percent change in body weight was -15.0% with tirzepatide 5 mg, -19.5% with 10 mg, and -20.9% with 15 mg, versus -3.1% with placebo over 72 weeks. In SURMOUNT-OSA, published in 2024, the apnea-hypopnea index decreased by 25.3 events/hour with tirzepatide versus 5.3 events/hour with placebo at week 52 among participants not receiving PAP therapy at baseline.

Does the brand name affect your insurance coverage?

Yes — your plan builds its own formulary and evaluates the brand and the indication on the prescription, not the fact that both products contain tirzepatide. Most patients meet that decision as a prior authorization; Measured states that many plans require one before covering brand-name GLP-1s such as Ozempic, Wegovy, Mounjaro, or Zepbound, and approval is not a promise of payment. (More in does insurance cover GLP-1 weight loss medications.)

The two brands can land differently here because of what they treat, not the molecule: Medicare Part D has long excluded "agents when used for weight loss," so Mounjaro's diabetes indication is generally Part D-eligible in a way a weight-reduction drug is not — which is why Zepbound needed a separate bridge program to reach Part D patients (below). If either drug is denied, you can appeal the decision or ask your plan about its exceptions process.

For patients with commercial insurance, Measured performs a benefits check and its concierge team submits prior authorizations on the patient's behalf, working with plans including Aetna, Anthem, Blue Cross Blue Shield, Cigna, and UnitedHealthcare.

Which one will I be prescribed, Mounjaro or Zepbound?

The indication decides which brand applies to you. If you have type 2 diabetes, Mounjaro's approved use applies: glycemic control in adults and pediatric patients 10 years of age and older.

If the goal is weight reduction, Zepbound's label is the relevant one. The obesity eligibility threshold used in the Zepbound weight-reduction registration trials was a BMI of 30 kg/m2 or greater, and the overweight eligibility threshold was a BMI of 27 to less than 30 kg/m2 together with at least one weight-related comorbid condition. For the weight-reduction indication, the recommended Zepbound maintenance dosages are 5 mg, 10 mg, or 15 mg injected subcutaneously once weekly.

Obstructive sleep apnea is a separate approved indication. The OSA registration trials for Zepbound enrolled adults with moderate to severe OSA defined as an apnea-hypopnea index (AHI) of 15 or greater, in patients with obesity (BMI 30 kg/m2 or greater). For the OSA indication, the recommended Zepbound maintenance dosage is 10 mg or 15 mg injected subcutaneously once weekly.

Both Zepbound indications are limited to adults; the safety and effectiveness of Zepbound have not been established in pediatric patients.

What do Mounjaro and Zepbound cost if your plan doesn't cover them?

Last verified: August 21, 2026.

If your plan doesn't cover either drug, list price, Medicare's GLP-1 Bridge, and self-pay are the fallback paths — here is how the numbers break down. Eli Lilly's wholesale acquisition cost (list price) for Mounjaro is $1,079.77 per carton of four single-dose pens as of its January 2, 2025 disclosure, the same price at every strength from 2.5 mg/0.5 mL through 15 mg/0.5 mL.

For Medicare Part D, eligible beneficiaries can obtain Zepbound for a $50 per month copay through the Medicare GLP-1 Bridge demonstration as of August 5, 2026, regardless of Part D benefit phase; the Bridge runs July 1, 2026 through December 31, 2027, covers only the Zepbound KwikPen formulation, and applies when Zepbound is used to reduce and maintain weight loss. Mounjaro is not part of the Bridge — its Part D coverage runs through the ordinary diabetes-drug pathway described above.

Without insurance, Measured lists Zepbound as available "with or without insurance" and Mounjaro as "insurance required," with medication priced separately from membership. Current self-pay options, including compounded alternatives, are on the medications page.

Can I switch between Mounjaro and Zepbound?

Yes, with a new prescription — the strengths, titration steps, and missed-dose rule are identical between the two brands. Some people move between the two brands when their coverage changes mid-treatment. From the labels: the strengths available are the same, the titration steps are the same, and both labels give the same missed-dose rule — administer the missed dose as soon as possible within 4 days (96 hours); if more than 4 days have passed, skip the missed dose and resume the regular weekly schedule.

How a switch plays out — dose continuity, mid-year brand changes, existing authorizations — belongs to your prescriber and your plan.

Where to check the rest

Pricing, plan tiering, and pharmacy substitution rules change faster than FDA labels do, so this page sticks to the labels and dated price sheets in its sources. For self-pay prices, current formulary placement, and whether a given brand is in the Medicare GLP-1 Bridge, check your plan documents and the manufacturer pages linked in the sources.