Mounjaro (tirzepatide) activates GIP and GLP-1 receptors; Ozempic (semaglutide) activates GLP-1 only, and in their head-to-head trial tirzepatide won on both A1C and weight.
The SURPASS-2 trial randomized people with type 2 diabetes on metformin to tirzepatide 5, 10, or 15 mg or semaglutide 1 mg for 40 weeks. Mean A1C fell 2.01, 2.24, and 2.30 percentage points on the three tirzepatide doses versus 1.86 points on semaglutide, and tirzepatide was superior at every dose. Body weight fell more too, with treatment differences of 1.9, 3.6, and 5.5 kg. The most common adverse events in both groups were gastrointestinal. One caveat for a fair reading: the trial used semaglutide 1 mg, not the higher 2 mg dose approved later for diabetes. Both molecules have weight-loss brand versions (Zepbound and Wegovy). Neither trial result overrides individual factors like your other medications, kidney function, or what your plan covers.
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Common questions
What is the difference between Mounjaro and Ozempic?
Mounjaro and Ozempic are both once-weekly injections for type 2 diabetes, but they contain different active drugs. Ozempic is semaglutide, a GLP-1 receptor agonist. Mounjaro is tirzepatide, which targets both GIP and GLP-1 receptors. They were compared directly in the SURPASS-2 trial, a 40-week study in people with type 2 diabetes on metformin. Tirzepatide lowered A1C more at every dose: -2.01, -2.24, and -2.30 percentage points at 5, 10, and 15 mg, versus -1.86 points on semaglutide 1 mg. Weight loss also favored tirzepatide, by 1.9 kg, 3.6 kg, and 5.5 kg across the three doses. Gastrointestinal side effects (nausea, vomiting, diarrhea) were the most common in both groups. One nuance: SURPASS-2 tested tirzepatide against semaglutide 1 mg, which was Ozempic's highest approved dose at the time. Both drugs also exist under weight-management brand names, Zepbound (tirzepatide) and Wegovy (semaglutide). If you are choosing between them for diabetes, the evidence favors tirzepatide on average, but your other conditions, other medications, and insurance coverage all matter.