Tirzepatide vs. Semaglutide: Which Is Better for Weight Loss?
Published June 2026 | 8 min read
If you are comparing weight-loss medications, two names come up more than any others: tirzepatide and semaglutide. Both are injectable medications that have changed what is possible with medical weight management, and both work on the same appetite-regulating system in the body. The question most people want answered is simple: which one takes off more weight? In the first trial that tested them directly against each other, tirzepatide came out ahead. The fuller answer depends on more than a single number, so here is what the research actually shows and what it means for choosing between them.
Key takeaways
- In the first head-to-head trial, people on tirzepatide lost more weight on average than those on semaglutide, roughly 20 percent versus 14 percent of body weight. [3]
- Both are highly effective compared with older weight-loss treatments. The right choice depends on your health history, how you tolerate the medication, and your provider's guidance.
- Weight tends to return after stopping either medication, so both work best as part of an ongoing, supervised plan. [5][6]
How these medications work
Semaglutide and tirzepatide both belong to a class of medications that mimic gut hormones your body releases after you eat. Semaglutide acts on a single receptor, GLP-1, which helps regulate appetite and how full you feel. [4] Tirzepatide acts on two receptors, GLP-1 and GIP, which is why it is sometimes described as a dual-action medication. [4] In practice, both reduce hunger, slow how quickly the stomach empties, and make it easier to eat less without feeling deprived. They are taken as a once-weekly injection alongside changes to diet and activity, and they are meant to treat weight as an ongoing medical condition rather than to force a quick, temporary drop.
How much weight does semaglutide lead to?
In its landmark obesity trial, known as STEP 1, adults taking semaglutide lost an average of about 14.9 percent of their body weight over 68 weeks, compared with about 2.4 percent for those on a placebo. [1] More than two-thirds of participants lost at least 10 percent of their weight, and about half lost 15 percent or more. [1] Those results held up over time. In a two-year study, the average reduction was still about 15 percent at 104 weeks, which showed the effect lasts as long as treatment continues. [7]
How much weight does tirzepatide lead to?
Tirzepatide was studied in a parallel obesity trial called SURMOUNT-1. At its highest dose, participants lost up to about 20.9 percent of their body weight over 72 weeks, again compared with only a small change on placebo. [2] The effect was dose-dependent, meaning higher doses produced more weight loss, and a notable share of participants reached very large reductions. [2] One note on names that often causes confusion: tirzepatide is sold under two brands, Mounjaro for type 2 diabetes and Zepbound for weight management. They are the same medication.
The head-to-head trial
Comparing two separate trials only goes so far, because they enrolled different people under different conditions. In 2025, a trial called SURMOUNT-5 tested the two medications directly against each other. Over 72 weeks, the tirzepatide group lost an average of 20.2 percent of body weight, while the semaglutide group lost 13.7 percent. [3] The gap was even wider at the deepest level of weight loss: nearly 20 percent of people on tirzepatide lost at least 30 percent of their body weight, compared with about 7 percent of those on semaglutide. [3] The table below summarizes the key results.
| Tirzepatide | Semaglutide | |
|---|---|---|
| Avg weight lost (head-to-head) | 20.2% | 13.7% |
| Lost 30%+ of body weight | 19.7% | 6.9% |
| Stopped due to side effects | 2.7% | 5.6% |
| How it is taken | Weekly injection | Weekly injection |
Side effects and tolerability
The two medications have similar side-effect profiles. The most common effects are gastrointestinal, including nausea, diarrhea, constipation, and stomach discomfort, and they most often appear while the dose is being increased. [4] For most people these effects ease over time as the body adjusts, which is why both medications are started at a low dose and raised gradually. In the head-to-head trial, slightly fewer people stopped tirzepatide because of side effects than stopped semaglutide, 2.7 percent versus 5.6 percent, which suggests the two are broadly comparable in how well they are tolerated. [3] Side effects still vary from person to person, and a provider can help you manage them or adjust your plan.
What happens if you stop?
Both medications treat weight as an ongoing condition rather than a one-time fix, and the research is clear that stopping leads to weight regain for most people. In maintenance studies, participants who came off treatment regained a meaningful share of the weight they had lost, while those who stayed on it kept the large majority of their results. [5][6] This is not a sign that the medication failed. It reflects the underlying biology of weight regulation, which is why these medications work best as part of a long-term, supervised program that pairs the medication with sustainable changes to eating and activity.
Which one is right for you?
On the numbers alone, tirzepatide produced more weight loss than semaglutide in the head-to-head trial. But the best medication for you is not only about the biggest average result. Your health history, any other conditions you have, how well you tolerate the medication, your goals, and cost and availability all matter. Some people do very well on semaglutide and never need to consider anything else. The right path is a conversation with a licensed provider who can look at your full picture and recommend an option that fits.
Frequently asked questions
- Wilding JPH, et al. STEP 1. N Engl J Med. 2021. pubmed.ncbi.nlm.nih.gov/33567185
- Jastreboff AM, et al. SURMOUNT-1. N Engl J Med. 2022. pubmed.ncbi.nlm.nih.gov/35658024
- Aronne LJ, et al. SURMOUNT-5. N Engl J Med. 2025. pubmed.ncbi.nlm.nih.gov/40353578
- ZEPBOUND (tirzepatide) Prescribing Information. U.S. FDA / DailyMed.
- Aronne LJ, et al. SURMOUNT-4. JAMA. 2024. pubmed.ncbi.nlm.nih.gov/38078870
- Rubino D, et al. STEP 4. JAMA. 2021. pubmed.ncbi.nlm.nih.gov/33755728
- Garvey WT, et al. STEP 5. Nat Med. 2022. pmc.ncbi.nlm.nih.gov/articles/PMC9556320