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| Mounjaro | Tirzepatide | |
|---|---|---|
| What it is | Eli Lilly's brand-name prescription injection made with tirzepatide12 | The active ingredient: a peptide that activates both the GIP and GLP-1 receptors1 |
| Active ingredient | Tirzepatide1 | Tirzepatide itself, sold in the US as Mounjaro and Zepbound14 |
| Maker | Eli Lilly and Company2 | Eli Lilly holds both US brands; the 2018 discovery paper names it LY32981762413 |
| Form | Single-dose pens and vials (0.5 mL) and 4-dose KwikPens and vials (2.4 mL), ready to inject1 | A solution injected under the skin once a week in both US brands15 |
| Approved uses | Type 2 diabetes: blood sugar control in adults and children 10 and older, and lower major cardiovascular event risk in high-risk adults1 | As Zepbound: long-term weight reduction, and moderate to severe sleep apnea in adults with obesity; as Mounjaro: the diabetes uses41 |
| Dosing schedule | 2.5 mg once weekly to start, raised in 2.5 mg steps after at least 4 weeks; maximum 15 mg (10 mg in children)1 | Once weekly in both brands; Zepbound maintenance is 5, 10 or 15 mg for weight and 10 or 15 mg for sleep apnea5 |
| First US approval | May 13, 20222 | 2022, as Mounjaro; Zepbound followed on November 8, 202327 |
Key differences
One ingredient, two US brand names
Tirzepatide is a molecule. Mounjaro is a finished, labeled product that Eli Lilly makes with it, and it is one of two US brands of tirzepatide.14 The other is Zepbound. Both come in the same six strengths, from 2.5 mg to 15 mg, but their labels cover different people.14
Mounjaro's label is about type 2 diabetes. It covers blood sugar control in adults and children 10 and older, and lowering the risk of heart attack, stroke or cardiovascular death in adults with type 2 diabetes at high risk.1 Zepbound's label is about weight. It covers long-term weight reduction in adults with obesity, or overweight with at least one weight-related condition, and moderate to severe obstructive sleep apnea in adults with obesity.4 Weight loss is not a US indication for Mounjaro.1 The Zepbound label also says combining it with other tirzepatide-containing products, Mounjaro included, is not recommended.4
The approvals came in steps. FDA approved Mounjaro on May 13, 2022, as a new molecular entity with priority review.2 On December 19, 2025, it extended the diabetes use to children 10 and older.21 On August 27, 2026, it added the cardiovascular indication, based on the SURPASS-CVOT trial.3 Zepbound was approved on November 8, 2023, for chronic weight management.7 On December 20, 2024, it gained a sleep apnea indication, which FDA called the first drug treatment option for certain patients with the condition.8
What the molecule is
Tirzepatide is a peptide. KEGG lists its sequence of 39 amino acids.12 A 2018 discovery paper describes it, under the code LY3298176, as a dual GIP and GLP-1 receptor agonist.13 The Mounjaro label explains the design. The chain is based on the GIP hormone sequence, carries aminoisobutyric acid at positions 2 and 13, and has a C20 fatty diacid on the lysine at position 20.1 That fatty chain lets the molecule bind albumin in the blood, which prolongs its half-life to about 5 days; Mounjaro is given once a week.1 In the body, tirzepatide raises insulin release and lowers glucagon, both in a glucose-dependent way, and it delays stomach emptying.1
Two trial programs behind one molecule
Each brand rests on its own trials. Mounjaro's label summarizes the SURPASS trials in type 2 diabetes. In SURPASS-1, 478 adults took Mounjaro alone or placebo for 40 weeks, and HbA1c fell 1.7 to 1.8 percentage points on 5 to 15 mg vs 0.1 on placebo.1 In SURPASS-CVOT, 13,299 adults with type 2 diabetes and heart or blood vessel disease took Mounjaro or dulaglutide and were followed for a median of 210.1 weeks. A first major cardiovascular event occurred in 12.1% vs 13.0% (hazard ratio 0.92). Mounjaro was non-inferior, but superiority was not shown.1
Zepbound's label summarizes the SURMOUNT trials in obesity. In the first, 2,539 adults with obesity, or overweight plus a weight-related condition, and no type 2 diabetes took 5, 10 or 15 mg or placebo for 72 weeks. Average weight change was -15.0%, -19.5% and -20.9%, vs -3.1% on placebo.6 Weight also fell in Mounjaro's diabetes trials, by about 5.4 to 11.3 kg over 40 to 52 weeks. The Mounjaro label does not turn that into a weight indication.1
Dose rules on the two labels
Both labels start at 2.5 mg once a week and raise the dose in 2.5 mg steps after at least 4 weeks, up to 15 mg.15 They differ at the low end. Since August 2026, the Mounjaro label allows 2.5 mg for ongoing blood sugar control; before that it was a starting dose only.31 Zepbound still treats 2.5 mg as a starting dose, with maintenance at 5, 10 or 15 mg for weight and 10 or 15 mg for sleep apnea.5 Children 10 and older on Mounjaro stop at 10 mg.1 The prescriber chooses the dose and the timing of each step, weighing response and tolerability.5
Outside the United States
The brand split differs by market. In the European Union, tirzepatide has been authorized under the Mounjaro name since September 15, 2022.9 That authorization includes weight management in adults with a BMI of 30 or more, or 27 to under 30 with a weight-related condition.9 So "Mounjaro for weight" means different things in different markets.
Tirzepatide products that are not Mounjaro
Not every product that lists tirzepatide is Mounjaro. FDA says compounded drugs are not FDA approved and are not reviewed for safety, effectiveness or quality before they are marketed.11 In an order dated December 19, 2024, FDA determined that the shortage of tirzepatide injection products is resolved.10 As of May 31, 2026, FDA had received more than 730 reports of adverse events associated with compounded tirzepatide.11 FDA has also warned companies that illegally sold unapproved tirzepatide falsely labeled "for research purposes" or "not for human consumption" directly to consumers for human use, and it calls these products of unknown quality.11 The label facts on this page apply only to Mounjaro and Zepbound as Lilly makes them.
Which page to read next
For the full label picture, read What is Mounjaro?, then the Mounjaro dosage and Mounjaro side effects pages. The tirzepatide profile covers the compound and the research on it, and What is Zepbound? covers the weight brand. To see where tirzepatide sits among GLP-1 drugs, read GLP-1 vs Mounjaro or Mounjaro vs Ozempic. Every pair is listed on the GLP-1 comparisons page.
Frequently asked questions
Is tirzepatide the same as Mounjaro?
Mounjaro contains tirzepatide, but the two words name different things. Tirzepatide is the active ingredient. Mounjaro is one FDA-approved product made with it, labeled for adults and children 10 and older with type 2 diabetes.1 Zepbound is Lilly's other tirzepatide brand, labeled for weight reduction and sleep apnea.4 FDA has warned companies that sold unapproved tirzepatide falsely labeled 'for research purposes' to consumers, and says unapproved versions do not undergo its review for safety, effectiveness and quality.11
Is Zepbound the same as Mounjaro?
Same molecule, different labels. Both contain tirzepatide, both are made by Eli Lilly, and both come in the same six strengths, from 2.5 mg to 15 mg.14 Mounjaro is approved for type 2 diabetes.1 Zepbound is approved for long-term weight reduction in adults with obesity, or overweight plus a weight-related condition, and for moderate to severe obstructive sleep apnea in adults with obesity.4 The Zepbound label says using it with other tirzepatide-containing products, such as Mounjaro, is not recommended.4
Can Mounjaro be used for weight loss only?
Not under its US label. Mounjaro's FDA indications are blood sugar control in type 2 diabetes and lowering major cardiovascular event risk in high-risk adults with type 2 diabetes.1 Weight was measured in its diabetes trials, where adults lost about 5.4 to 11.3 kg over 40 to 52 weeks on 5 to 15 mg.1 In the US, the tirzepatide brand approved for weight reduction is Zepbound.4 In the European Union, the Mounjaro authorization itself also covers weight management in adults.9
Is tirzepatide FDA approved?
Yes, as the active ingredient of two prescription brands. FDA approved Mounjaro on May 13, 2022, as a new molecular entity,2 and Zepbound on November 8, 2023, for chronic weight management.7 Those approvals cover the products as Eli Lilly makes and labels them; FDA says unapproved versions, including compounded tirzepatide, do not undergo its review for safety, effectiveness and quality.11 In an order dated December 19, 2024, FDA determined that the shortage of tirzepatide injection products, which began in December 2022, is resolved.10
What is the Mounjaro 2.5 mg dose for?
It is the starting dose. Since the August 2026 label update, 2.5 mg once weekly may also be used for ongoing blood sugar control; earlier labels said it was for starting treatment only.13 On the Zepbound label, 2.5 mg is still a starting dose only, used for 4 weeks before the first step up to 5 mg.5 In both cases the prescriber sets the dose and decides when to raise it, weighing response and tolerability.5
Is tirzepatide a peptide?
Yes. KEGG lists tirzepatide as a chain of 39 amino acids.12 The Mounjaro label describes a chain built on the GIP hormone sequence, with aminoisobutyric acid at positions 2 and 13, an amidated end, and a C20 fatty diacid on the lysine at position 20. That fatty chain binds albumin in the blood and stretches the half-life to about 5 days. The formula is C225H348N48O68 and the molecular weight is 4813.53 Da.1
Written by D2C Peptides Editorial Team.
Pending qualified review.
Updated .
Sources
- MOUNJARO (tirzepatide) injection Prescribing Information, Medication Guide and Instructions for Use, revised 08/2026 (NDA 215866/S-044, S-045). U.S. Food and Drug Administration (Drugs@FDA), 2026.
- Drugs@FDA: NDA 215866, Mounjaro (tirzepatide) application overview. U.S. Food and Drug Administration, 2026.
- FDA supplement approval letter, NDA 215866/S-044 and S-045 (Mounjaro), signed 08/27/2026. U.S. Food and Drug Administration, 2026.
- Zepbound Prescribing Information, revised 08/2026 (NDA 217806/S-041): Section 1 Indications and Usage. Eli Lilly and Company; posted by U.S. Food and Drug Administration, 2026.
- Same source as 4: Sections 2.1 and 2.2 Dose Escalation, Maintenance and Maximum Dosage.
- Same source as 4: Section 14.1 Weight Reduction Studies 1, 2 and 3 (Tables 2 to 5).
- FDA Approves New Medication for Chronic Weight Management (news release, November 8, 2023). U.S. Food and Drug Administration, 2023.
- FDA Approves First Medication for Obstructive Sleep Apnea (news release, December 20, 2024). U.S. Food and Drug Administration, 2024.
- Mounjaro (tirzepatide) EPAR overview, page last updated 08/10/2026. European Medicines Agency, 2026.
- Declaratory Order: Resolution of Shortages of Tirzepatide Injection Products (Mounjaro and Zepbound), December 19, 2024. U.S. Food and Drug Administration, 2024.
- FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss (content current as of 10/01/2026). U.S. Food and Drug Administration, 2026.
- KEGG DRUG D11360: Tirzepatide. KEGG, Kanehisa Laboratories, 2026.
- LY3298176, a novel dual GIP and GLP-1 receptor agonist for the treatment of type 2 diabetes mellitus: From discovery to clinical proof of concept (Coskun et al.). Molecular Metabolism, 2018.