Also known as: Mounjaro, Zepbound, LY3298176
Half-life: ~5 days (120 hours)
Tirzepatide is a first-in-class dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist developed by Eli Lilly and Company. As a "twincretin," it simultaneously activates both incretin receptor pathways, producing metabolic effects that exceed those of selective GLP-1 agonists alone. The 39-amino-acid synthetic peptide is based on the GIP sequence with specific amino acid substitutions and a C20 fatty acid chain that enables albumin binding for a half-life of approximately 5 days.
Clinical trials have demonstrated weight loss results surpassing any previously approved pharmacotherapy. The SURMOUNT-1 trial showed that tirzepatide at the highest dose (15 mg) produced an average weight loss of 22.5% of body weight over 72 weeks in adults with obesity — a result that approaches the efficacy of bariatric surgery. The SURPASS program for type 2 diabetes similarly showed superior glycemic control compared to semaglutide and other comparators, with a significant proportion of patients achieving HbA1c levels below 5.7%.
The dual receptor mechanism is believed to provide complementary metabolic benefits: GLP-1 receptor activation reduces appetite and slows gastric emptying, while GIP receptor activation may enhance fat metabolism, improve insulin sensitivity, and contribute to the overall superior efficacy profile. Tirzepatide was approved as Mounjaro for type 2 diabetes in May 2022 and as Zepbound for chronic weight management in November 2023. In December 2024, it also received approval for moderate-to-severe obstructive sleep apnea in adults with obesity.
Tirzepatide was developed by Eli Lilly and Company, representing a novel "twincretin" approach by targeting both GIP and GLP-1 receptors simultaneously. The compound (LY3298176) is a 39-amino-acid synthetic peptide based on the GIP sequence, engineered with specific substitutions and a C20 fatty acid chain for extended duration. Phase 2 results published in The Lancet (2018) generated significant excitement. The SURPASS trial program for diabetes and SURMOUNT trials for obesity delivered unprecedented results. FDA approved Mounjaro for type 2 diabetes in May 2022 and Zepbound for chronic weight management in November 2023. In December 2024, it also received approval for moderate-to-severe obstructive sleep apnea in adults with obesity.
Tirzepatide's tolerability is similar to other GLP-1 class medications, with gastrointestinal side effects being the primary concern. Nausea, diarrhea, and decreased appetite are most common during dose escalation. In the SURMOUNT-1 trial, approximately 4.3-7.1% of participants discontinued due to adverse events across dose groups. The slow titration schedule (starting at 2.5 mg and increasing every 4 weeks) is critical for tolerability. Most GI side effects are mild to moderate and transient. Serious adverse events were infrequent in clinical trials, and the overall safety profile supported FDA approval for multiple indications.
Dose Range
2500-15000 mcg
Frequency
Once weekly (SubQ)
Duration
Ongoing as prescribed
Dose Range
2500-15000 mcg
Frequency
Once weekly (SubQ, titrated over 20 weeks)
Duration
Ongoing as prescribed
Dosing information is for educational purposes only. Consult a healthcare professional before using any peptide.
Typical Vial Size
5 mg
Water Type
Pre-filled pen (pharmaceutical) — no reconstitution needed
Mixing Volume
N/A (pre-filled) mL
Half-Life
~5 days (120 hours)
Molecular Weight
4813.5 Da
Mounjaro/Zepbound are supplied as pre-filled single-dose pens. Store refrigerated at 2-8°C. May be stored at room temperature (up to 30°C) for up to 21 days. Compounded tirzepatide is reconstituted with bacteriostatic water.
FDA Status
FDA approved. Mounjaro (2022) for type 2 diabetes, Zepbound (2023) for chronic weight management, and (2024) for obstructive sleep apnea in adults with obesity.
Legal Status
Prescription medication. Available through pharmacies with valid prescription. Compounded versions available through 503B pharmacies.
USA
ApprovedMounjaro (2022), Zepbound (2023), also for sleep apnea (2024)
EU
ApprovedEMA authorized Mounjaro for type 2 diabetes 2022
UK
ApprovedNICE recommended Mounjaro for diabetes
Australia
ApprovedTGA approved Mounjaro
Canada
ApprovedHealth Canada approved for diabetes
Japan
ApprovedApproved for type 2 diabetes 2022
Jastreboff AM, Aronne LJ, Ahmad NN, Wharton S, Connery L, Alves B, Kiyosue A, Zhang S, Liu B, Bunck MC, Stefanski A
New England Journal of Medicine (2022)
SURMOUNT-1 trial demonstrating that tirzepatide produced mean weight reductions of 15.0% (5 mg), 19.5% (10 mg), and 20.9% (15 mg) versus 3.1% with placebo over 72 weeks.
View Study →Frias JP, Davies MJ, Rosenstock J, Perez Manghi FC, Fernandez Lando L, Bergman BK, Liu B, Cui X, Brown K
New England Journal of Medicine (2021)
SURPASS-2 trial showing tirzepatide was superior to semaglutide 1 mg in reducing HbA1c and body weight across all dose levels in patients with type 2 diabetes.
View Study →Nauck MA, Meier JJ
The Lancet Diabetes & Endocrinology (2021)
Comprehensive review of the scientific rationale for dual GIP/GLP-1 receptor agonism and its therapeutic potential in metabolic disease.
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