Mounjaro vs Zepbound: Same Drug, Two Labels Compared
The short answer
Mounjaro and Zepbound are the same drug, tirzepatide from Eli Lilly, in the same 2.5 to 15 mg once-weekly strengths. The Mounjaro label covers type 2 diabetes and cardiovascular risk reduction in adults with type 2 diabetes at high risk. The Zepbound label covers weight reduction and obstructive sleep apnea in adults with obesity.
Mounjaro and Zepbound are two brand names for the same medicine, tirzepatide, made by Eli Lilly. A search for one is a search for the other: the molecule, the strengths and the injection are the same, and what differs is which conditions each brand's FDA label covers. This page sets the two US labels side by side. It is a research reference, not medical advice.
Mounjaro vs Zepbound at a glance
| What | Mounjaro | Zepbound |
|---|---|---|
| Active ingredient | Tirzepatide (GIP and GLP-1 receptor agonist) | Tirzepatide (GIP and GLP-1 receptor agonist) |
| Maker | Eli Lilly | Eli Lilly |
| What the label covers | Type 2 diabetes in adults and in children aged 10 and over (glycemic control); lowering the risk of major cardiovascular events in adults with type 2 diabetes at high risk (Mounjaro label, rev. 8/2026) | Reducing excess body weight and keeping it off in adults with obesity, or overweight plus one weight-related condition; moderate to severe obstructive sleep apnea in adults with obesity (Zepbound label, rev. 8/2026) |
| Starting dose | 2.5 mg once weekly | 2.5 mg once weekly for 4 weeks (initiation only) |
| Dose steps | 2.5 mg increments after at least 4 weeks on the current dose, if more glycemic control is needed | Up to 5 mg after 4 weeks, then 2.5 mg increments, each after at least 4 weeks |
| Doses used long term | Titrated to glycemic control, up to 15 mg in adults (10 mg in children) | 5, 10 or 15 mg for weight; 10 or 15 mg for sleep apnea |
| Maximum dose | 15 mg once weekly in adults; 10 mg in pediatric patients | 15 mg once weekly |
| Forms | Single-dose pen or vial (2.5 to 15 mg in 0.5 mL), multi-dose vial, KwikPen | Single-dose pen or vial (2.5 to 15 mg in 0.5 mL), multi-dose vial, KwikPen |
| Boxed warning | Risk of thyroid C-cell tumors | Risk of thyroid C-cell tumors |
The strengths and forms in the two labels are the same list. The label for each brand is what its prescriber works from, so a diabetes label dose schedule and a weight-loss label dose schedule are not interchangeable on paper, even though the molecule is.
Why the side effect tables look different
The two labels report different percentages for the same drug, which can look like a contradiction. It is not: each table comes from different trials in different people. The Mounjaro table pools placebo-controlled studies in adults with type 2 diabetes; the Zepbound table pools SURMOUNT-1 and SURMOUNT-2 in adults with obesity.
| Reaction | Mounjaro (placebo) | Zepbound (placebo) |
|---|---|---|
| Nausea | 12%, 15%, 18% (4%) | 25%, 29%, 28% (8%) |
| Diarrhea | 12%, 13%, 17% (9%) | 19%, 21%, 23% (8%) |
| Vomiting | 5%, 5%, 9% (2%) | 8%, 11%, 13% (2%) |
| Constipation | 6%, 6%, 7% (1%) | 17%, 14%, 11% (5%) |
| Decreased appetite | 5%, 10%, 11% (1%) | Not in the label table |
Sources: the Mounjaro label (placebo-controlled pool, 235 on placebo and about 240 per tirzepatide dose) and the Zepbound label (pooled Studies 1 and 2, 958 on placebo). Reading across the two tables is a comparison of populations as much as of brands.
Weight loss in the Zepbound trial
The weight data on the Zepbound side come from SURMOUNT-1, which enrolled 2,539 adults with obesity or overweight and no diabetes for 72 weeks. Mean weight change was -15.0% at 5 mg, -19.5% at 10 mg and -20.9% at 15 mg, against -3.1% on placebo (NEJM 2022). The Mounjaro label notes that tirzepatide lowers body weight in people with type 2 diabetes, but weight reduction is not one of its listed indications.
Can Mounjaro be used for weight loss?
Doctors can prescribe an approved drug for a use outside its label, and coverage rules then depend on the insurer. That is a decision between a patient, a prescriber and a payer, and the labels above show what each brand has been formally approved for. For the full trial picture on weight, see the Zepbound guide and tirzepatide before and after.
Storage and handling
The storage limits come from each brand's label and depend on the form. A Mounjaro KwikPen or multi-dose vial lasts 30 days once opened, while a single-dose pen or vial may spend up to 21 days in total out of the fridge. The details are in Mounjaro storage and Zepbound storage.
Research-grade tirzepatide
Neither brand name applies to compounded or research-grade tirzepatide, which is covered separately in compounded tirzepatide and the tirzepatide dosage guide. If you are working from a vial, the calculator turns vial strength, water volume and dose into a syringe mark.
Calculate your draw for tirzepatide
Enter the vial strength, the bacteriostatic water you added and your dose, and get the exact mark on the syringe. Free, no signup, and the result comes with a link you can share or save.
Open the tirzepatide calculator peptulator.com, the Bureau's independent toolComparing tirzepatide with the other big weekly injection? See Zepbound vs Wegovy.
Not sure which of these you actually need?
Answer five questions about your goal, experience and budget and the Stack Builder shows you a matched research protocol on screen, with the compounds, cycle shape and vendor picks from the six vendors we score.
Build your stack, 2 minutesSee also: Ozempic vs Mounjaro.
Frequently asked questions
Is Mounjaro the same as Zepbound?
Yes in the sense that matters for the molecule: both contain tirzepatide from Eli Lilly, in the same strengths, as a once-weekly injection under the skin. They are sold under separate brand names with separate FDA labels for different conditions.
What is Mounjaro approved for?
The Mounjaro label (revised August 2026) lists improving glycemic control in adults and children aged 10 and over with type 2 diabetes, and lowering the risk of major cardiovascular events in adults with type 2 diabetes who are at high risk.
What is Zepbound approved for?
The Zepbound label (revised August 2026) lists reducing excess body weight and maintaining the reduction long term in adults with obesity, or with overweight plus a weight-related condition, and treating moderate to severe obstructive sleep apnea in adults with obesity.
Why do Mounjaro and Zepbound show different side effect rates?
The labels pool different trials in different people. The Mounjaro table is built from studies in adults with type 2 diabetes, the Zepbound table from SURMOUNT-1 and SURMOUNT-2 in adults with obesity, so the percentages reflect the populations as well as the brands.
Sources (checked 6 November 2026)
- Mounjaro prescribing information, Eli Lilly, revised 8/2026, DailyMed. Checked 6 November 2026.
- Zepbound prescribing information and Medication Guide, Eli Lilly, revised 8/2026, DailyMed. Checked 6 November 2026.
- Jastreboff et al, Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1), New England Journal of Medicine, 2022. Checked 6 November 2026.
Label figures are from the Mounjaro and Zepbound labels revised August 2026. Labels and trial records change; the leaflet in your box and your prescriber come first. Educational content, not medical advice.