Semaglutide vs Tirzepatide
Both are weekly injections approved for type 2 diabetes and weight management. Tirzepatide acts on one more hormone receptor than semaglutide, and in trials it produced more weight loss on average.
At a glance
The facts side by side. Tap a name for its calculator.
| Semaglutide | Tirzepatide |
|---|---|
| Evidence | |
| Approved drug. Sold as Ozempic and Wegovy. | Approved drug. Sold as Mounjaro and Zepbound. |
| Vial sizes | |
| 2, 3, 5, 10 mg | 5, 10, 15, 30 mg |
| Usual dose range | |
| 0.25–2.4 mg | 2.5–15 mg |
| How often | |
| Weekly | Weekly |
| Unmixed | |
| Freezer −20°C | Freezer −20°C |
| After mixing | |
| Fridge 2–8°C, use within 28 days | Fridge 2–8°C, use within 28 days |
How they work
Semaglutide copies one gut hormone, GLP-1. Tirzepatide copies two, GLP-1 and GIP. Both slow stomach emptying and reduce appetite; the extra GIP action is thought to be part of why tirzepatide produced more weight loss in trials.
Weight loss in trials
In STEP 1, people on semaglutide 2.4 mg lost about 15% of their body weight on average over 68 weeks. In SURMOUNT-1, people on tirzepatide 15 mg lost about 21% over 72 weeks. In SURPASS-2, a head-to-head trial in people with type 2 diabetes, tirzepatide lowered weight and blood sugar more than semaglutide 1 mg. These are averages; individual results vary widely.
Dose steps
Both start low and step up no faster than every 4 weeks, to limit nausea. The approved semaglutide (Wegovy) steps are 0.25, 0.5, 1, 1.7 and 2.4 mg. The approved tirzepatide (Zepbound) steps are 2.5, 5, 7.5, 10, 12.5 and 15 mg. The right dose, and whether to step up at all, is for you and your prescriber to decide.
Side effects
The common ones are the same for both: nausea, vomiting, diarrhoea and constipation, mostly in the weeks after a dose goes up. Both carry the same warnings, including pancreatitis, gallbladder problems and a boxed warning about thyroid C-cell tumours seen in rodents.
Mixing and measuring
Vials of powder mix the same way for both, with bacteriostatic water. Semaglutide vials tend to be small (2 to 10 mg) and tirzepatide vials larger (5 to 30 mg), so the same number of units can be a very different dose. Always work it out from your own vial.
Track record
Semaglutide has been on the market longer (Ozempic 2017, Wegovy 2021), and large heart-outcome trials showed fewer heart attacks and strokes in people at high risk. Tirzepatide (Mounjaro 2022, Zepbound 2023) is newer, so there is less long-term data.
The short version
On average tirzepatide produces more weight loss; semaglutide has the longer track record and proven heart benefits. Which suits you is a decision to make with your prescriber. Pens from a pharmacy remove the mixing step, and the chance of a measuring mistake, entirely.