What is Tirzepatide?
Everything you need to know about the active ingredient in Mounjaro, the first "twincretin" for weight management.
Introduction
Tirzepatide is a prescription medication used for the treatment of type 2 diabetes and obesity. It is sold under the brand name Mounjaro (for diabetes and weight loss in the UK) and Zepbound (specifically for weight loss in the US).
It represents a new class of medications because it mimics the action of two different hormones, not just one.
How It Works
Tirzepatide is a dual GIP and GLP-1 receptor agonist. This means it activates receptors for two incretin hormones:
- GLP-1 (Glucagon-like peptide-1): Reduces appetite and slows digestion.
- GIP (Glucose-dependent insulinotropic polypeptide): Enhances insulin secretion and affects fat metabolism.
By targeting both pathways, Tirzepatide has been shown to be more effective for weight loss than medications that only target GLP-1 (like Semaglutide/Wegovy).
Clinical Efficacy
In the SURMOUNT-1 clinical trial, participants taking the highest dose of Tirzepatide (15mg) lost an average of 22.5% of their body weight over 72 weeks.
Key Stat
More than one-third of participants on the 15mg dose lost over 25% of their body weight.
Medical References & Sources
Last Medically Reviewed: April 2026