Tirzepatide

Tirzepatide is a weekly injectable developed by Eli Lilly that activates two gut-hormone receptors at once: GLP-1 and GIP (glucose-dependent insulinotropic polypeptide). It’s often grouped with the GLP-1s in everyday conversation, though it’s technically a dual agonist. Two brand names, one molecule:

• Mounjaro — approved for type 2 diabetes.
• Zepbound — approved for weight management and obstructive sleep apnea in people with obesity.

What the evidence shows

In the SURMOUNT-1 trial (Jastreboff et al., New England Journal of Medicine, 2022), adults on the highest dose (15 mg weekly) lost an average of 20.9% of body weight over 72 weeks; even the 5 mg dose averaged 15%. The SURMOUNT-5 head-to-head trial (2025) found greater average weight loss with tirzepatide than with semaglutide 2.4 mg.

Doses and side effects

Zepbound titrates from 2.5 mg up to a maximum of 15 mg in 4-week steps (see titration). The side-effect profile is similar to other GLP-1s — mostly gastrointestinal, mostly during dose escalation; roughly a quarter to a third of SURMOUNT-1 participants reported nausea at some point, most of it mild to moderate.

Practical notes

Like semaglutide, tirzepatide has a missed-dose window in its label (take within 4 days / 96 hours, otherwise skip — and confirm with your prescriber). And as with any GLP-1, average trial results say little about your week-to-week response — dose history and weight trends over months are what make your own pattern visible.