Tirzepatide arrived as a diabetes medication, Mounjaro, from Eli Lilly, approved by the FDA in May 2022, and was subsequently approved for chronic weight management as Zepbound in late 2023. It is now the drug patients ask about most often after semaglutide.
What makes it different
Semaglutide, the molecule in Ozempic and Wegovy, is a GLP-1 receptor agonist: it mimics one gut hormone involved in insulin release, gastric emptying and satiety. Tirzepatide acts on that same receptor and on the GIP receptor, a second incretin hormone. Hence "dual agonist."
This is worth stating precisely, because it is widely described incorrectly, including, until recently, on our own older pages. Tirzepatide is not a GLP-1 agonist combined with a DPP-4 inhibitor. It is a single molecule that activates two incretin receptors.
What that means in practice
In head-to-head trial data, tirzepatide has generally produced greater average weight reduction than semaglutide. Average is the operative word: trial averages describe populations, and the patient in front of us may respond better to either drug, or tolerate one and not the other.
The side-effect profile is broadly similar: gastrointestinal, front-loaded, and managed by escalating the dose gradually rather than starting where you intend to finish. Both are weekly injections. Both are contraindicated in patients with a personal or family history of medullary thyroid carcinoma or MEN2.
How the choice is actually made
Not by which one is newer. It is made on your metabolic bloodwork, your history, what you have already tried and how you tolerated it, availability, and cost over the length of a real program rather than a first month.
What matters more than the molecule is what surrounds it. Protein intake and resistance training decide how much of what you lose is fat rather than muscle, and that, in turn, decides how much comes back when you stop.
