Two molecules, four names
Semaglutide is sold as Ozempic (approved for type 2 diabetes, weekly injection up to 2 mg), Wegovy (approved for weight management, weekly injection 2.4 mg and now a 7.2 mg dose, plus a 25 mg daily tablet), and Rybelsus (daily tablet for diabetes).[1][2][3] Tirzepatide is sold as Mounjaro (type 2 diabetes) and Zepbound (weight management and obstructive sleep apnea), both weekly injections up to 15 mg.[4][5] Within each pair the drug is identical; the label, the approved uses and sometimes the pen differ.
The head-to-head trial
Only one large trial has compared the molecules directly in people without diabetes. In SURMOUNT-5, 751 adults took either tirzepatide or semaglutide at the highest dose they tolerated for 72 weeks. Weight fell 20.2% on tirzepatide and 13.7% on semaglutide; waist size fell 18.4 cm versus 13.0 cm.[6] The trial was funded by Lilly, tirzepatide's maker, and was open-label (people knew which drug they had), which are reasons to read the gap as real but not precise to the decimal.[6]
Side effects compared
The gut side effects are the same kind for both. In their own placebo-controlled trials, nausea was reported by 44% on Wegovy 2.4 mg and 25 to 29% on Zepbound, but those are different trials with different populations, not a comparison.[2][5] A network meta-analysis that lined up the trials indirectly found tirzepatide's gut tolerability at all doses similar to semaglutide 2.0 mg, with no difference in serious adverse events.[7] Zepbound's label lists injection-site reactions (6 to 8% versus 2%) more often than Wegovy's (1.4% versus 1%).[2][5] Both carry the same boxed warning about thyroid C-cell tumours in rodents.[2][5]
At a glance
| Brand | Molecule | Approved for | Weekly dose range | Pivotal weight result |
|---|---|---|---|---|
| Ozempic | semaglutide | type 2 diabetes; heart and kidney protection | 0.25 to 2 mg | not a weight-loss label |
| Wegovy | semaglutide | weight management; heart protection; MASH; (teens 12+) | 0.25 to 2.4 mg, or 7.2 mg; 25 mg daily tablet | −14.9% vs −2.4% at 68 wk[2] |
| Mounjaro | tirzepatide | type 2 diabetes | 2.5 to 15 mg | not a weight-loss label |
| Zepbound | tirzepatide | weight management; obstructive sleep apnea | 2.5 to 15 mg | −15.0 to −20.9% vs −3.1% at 72 wk[5] |
Heard vs evidence
The short version
Short on the way. A 35-second captioned version of this page is in production for the Fewer Bites channel. It will be embedded here when it is live.
Questions to bring to your prescriber
Print these or screenshot them. They are conversation starters, not a checklist of things to do.
- Which of these is on the table for me, and is that because of my diagnosis, my insurance, or the evidence?
- If I switch from one molecule to the other, how is the dose handled, and what side effects should I expect to restart?
- Do I have anything in my history (thyroid cancer in the family, pancreatitis, gallbladder disease, eye disease) that favours one over the other?
Education, not advice. This page explains what trials, labels and guidelines report. It does not tell anyone to start, change or stop a medicine. Your prescriber knows your history; this page does not.
Sources
- Novo Nordisk / FDA. Ozempic (semaglutide) prescribing information, revised 05/2026. label
- Novo Nordisk / FDA. Wegovy (semaglutide) injection and tablets, prescribing information, revised 06/2026. label
- Novo Nordisk / FDA. Rybelsus (oral semaglutide) prescribing information, revised 01/2026. label
- Eli Lilly / FDA. Mounjaro (tirzepatide) prescribing information, revised 08/2026. label
- Eli Lilly / FDA. Zepbound (tirzepatide) prescribing information, revised 08/2026. label
- Aronne LJ et al. Tirzepatide as compared with semaglutide for the treatment of obesity (SURMOUNT-5). N Engl J Med 2025. abstract only · RCT · industry-funded · open-label
- Karagiannis T et al. Subcutaneously administered tirzepatide vs semaglutide for adults with type 2 diabetes: systematic review and network meta-analysis. Diabetologia 2024. secondary · network meta-analysis (figures via Fewer Bites dossier)