When people compare weight loss shots, the real question is usually semaglutide vs tirzepatide. They are the two molecules behind the most talked about injections, and they do not work the same way or deliver the same results.
Semaglutide is sold as Ozempic and Wegovy. Tirzepatide is sold as Mounjaro and Zepbound. In head to head trials, tirzepatide leads on weight loss, but the right choice still depends on your health, your tolerance, and your budget.
Neither is available over the counter. Both need a prescription and medical supervision. This guide lines them up side by side so you walk into the appointment knowing what to ask.
Semaglutide vs tirzepatide: the quick comparison
Semaglutide and tirzepatide are both GLP-1 based weight loss drugs, but tirzepatide adds a second hormone and shows the bigger average weight loss in trials. Both are weekly injections that lower appetite and slow how fast the stomach empties.
The difference sits in the mechanism. Semaglutide mimics one gut hormone, GLP-1. Tirzepatide mimics two at once, GLP-1 and GIP, which helps explain the gap in results. When the two were tested directly, tirzepatide came out ahead in a head to head trial published in the NEJM.
| Molecule | Brands | Dosing | Average weight loss in trials |
|---|---|---|---|
| Semaglutide | Ozempic, Wegovy | once a week | about 15% (Wegovy 2.4 mg) |
| Tirzepatide | Mounjaro, Zepbound | once a week | about 20% (15 mg) |
If you want the full safety picture first, our guide on weight loss injection side effects covers what to expect on any of these drugs.
Semaglutide: Ozempic and Wegovy
Semaglutide is the better known of the two and shows up under two names that confuse people: Ozempic and Wegovy. Same molecule, different dose and different approved use.
Ozempic was built to treat type 2 diabetes, at doses up to 1 mg or 2 mg per week. People lost weight on it, so it became the household name. Using it purely for weight loss is off label.
Wegovy is the version made for obesity. Same semaglutide, but it climbs to 2.4 mg per week. In a 68 week trial, the average weight loss landed around 15% of body weight.
Ozempic and Wegovy carry the same molecule. The practical gap is the maximum dose and the label: Ozempic is approved for diabetes, Wegovy for treating obesity.
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Tirzepatide: Mounjaro and Zepbound
Tirzepatide is the newer molecule and the one with the largest average weight loss in trials, sold as Mounjaro and Zepbound. It works on two hormones at once, GLP-1 and GIP, while semaglutide works on one.
In the SURMOUNT-1 trial, over 72 weeks, the 15 mg dose led to an average loss near 20% of body weight. Mounjaro is the diabetes brand and Zepbound is the version approved for weight management.
More power often means more nausea at the start, which is why doctors step the dose up slowly. The trade off is the strongest result of the group when the treatment is tolerated.
Where liraglutide (Saxenda) fits
Liraglutide, sold as Saxenda, is the older daily option and lands below both semaglutide and tirzepatide on weight loss. In a 56 week trial it averaged around 8% of body weight.
It is a daily injection rather than weekly, which many people find harder to keep up. It still has a role, especially when a doctor wants a shorter acting option or when cost and access point that way.
Semaglutide vs tirzepatide: which should you choose
There is no single winner of semaglutide vs tirzepatide: the choice depends on your weight goal, your other conditions, how you tolerate the drug, and cost, always with a prescription.
If the biggest weight loss is the priority, tirzepatide tends to lead. If you value a longer track record or have a diabetes history, semaglutide is often the conversation. Insurance, supply, and side effects all move the decision in real life.
This is not a solo decision. A clinician weighs your labs, your history, and your other medications before picking the molecule and dose. If you are still at the access stage, see how to get Mounjaro.
Heads up: none of these are over the counter. They are prescription only, and the FDA has warned about unapproved compounded copies sold online. Stick to approved products through a licensed pharmacy.
The shot curbs appetite, but you still pick the plate
Semaglutide and tirzepatide lower hunger, they do not decide what goes on your plate. With appetite down, the new risk is eating so little that protein drops and you lose muscle along with fat.
That is where tracking your food pays off. When you can see how much protein you ate, it is easy to prioritize eggs, meat, fish and beans even without much hunger. Protected muscle is what holds the result after treatment ends.
The ContaCal app handles that part without a spreadsheet. You photograph the plate and the AI estimates calories and macros on the spot. To set the right target, learn how much protein per day you actually need.