Important: this page is educational. Tirzepatide is a prescription drug and requires a clinician evaluation.
What is tirzepatide?
Tirzepatide is a once-weekly injectable peptide that activates both the GLP-1 and GIP receptors. It is sold as Mounjaro for type 2 diabetes and Zepbound for chronic weight management. It was the first dual incretin to reach the market and has set the current ceiling for weight loss in a single-molecule therapy.
How does tirzepatide work?
GLP-1 activity drives appetite suppression and slowed gastric emptying. GIP activity appears to enhance insulin sensitivity, support fat oxidation, and improve tolerability by buffering some GLP-1 side effects. The combination produces a steeper weight curve and stronger glycemic effect than GLP-1 alone, with a roughly similar side-effect profile in trials.
Compare the two head to head in our tirzepatide vs semaglutide breakdown.
How is tirzepatide dosed?
Standard titration starts at 2.5 mg weekly for four weeks, then 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg. Most men land at 5 to 15 mg depending on response and tolerability. The four-week step interval is a minimum, not a maximum, and slower steps are common when nausea persists.
Trial data
In SURMOUNT-1, adults with obesity lost an average of 15 to 22.5 percent of body weight at 72 weeks depending on dose. SURPASS-2 showed superior A1c and weight reductions versus semaglutide 1 mg in type 2 diabetes. SURMOUNT-3 added a lifestyle lead-in and produced additional weight loss on top of that baseline.
How long until tirzepatide works?
Appetite changes within the first one to two weeks. Weight loss begins by week three or four. Peak effect on body composition takes nine to eighteen months at the dose a patient tolerates.
Side effects of tirzepatide
Nausea, diarrhea, constipation, and decreased appetite are the most common. Most are mild to moderate and dose-related. Less common issues include gallbladder events, injection-site reactions, and rare pancreatitis. As with semaglutide, muscle loss is a concern without adequate protein intake and resistance training.
Who should not take tirzepatide?
Contraindicated in MTC, MEN-2, and known hypersensitivity. Not recommended in active pancreatitis, severe gastroparesis, pregnancy, or breastfeeding. Use caution with concurrent insulin or sulfonylureas due to hypoglycemia risk.
Tirzepatide vs semaglutide
In SURMOUNT and SURPASS trials, tirzepatide produced greater weight loss and stronger A1c reductions than semaglutide at maximum doses. Tolerability was broadly similar. Cost, insurance, and supply often drive the practical choice. A clinician can map your goals and history to the right starting point.