Tirzepatide loses more weight than semaglutide on average. That is the short answer, and it holds up in the one trial that tested the two drugs directly. In a 72-week randomized study published in 2024, tirzepatide produced larger average reductions than semaglutide. The gap is real but modest for many people, and it is not the only thing that should decide the tirzepatide vs semaglutide question.
What did the head-to-head trial actually find?
Most of the internet compares these drugs using separate trials, which is a shaky way to do it. There is one proper randomized comparison: a study published in 2024 that put semaglutide against tirzepatide in adults with overweight or obesity over 72 weeks. Tirzepatide came out ahead on average weight reduction. You can see the design and full results in the published head-to-head report, which remains the strongest single piece of evidence on the direct question.
One trial is not the whole story, but it is worth more than any number of side-by-side figures pulled from studies that never enrolled the same people. When someone quotes a tidy percentage difference from stacking SURMOUNT against STEP, treat that with caution.
Why can’t the SURMOUNT and STEP numbers just be lined up?
Tirzepatide’s obesity evidence comes largely from the SURMOUNT program. Semaglutide’s comes from the STEP program. These were run separately, with different populations, entry criteria, and endpoints, so their headline percentages are not interchangeable. SURMOUNT-1, published in 2022, tested tirzepatide in adults with obesity and reported large average reductions across its dose groups; the details are in the SURMOUNT-1 report. That is a different experiment from any STEP trial, so subtracting one number from the other does not produce a valid comparison.
The STEP program answered questions the SURMOUNT trials did not. STEP 8, published in 2022, compared weekly semaglutide against daily liraglutide and placebo, showing semaglutide’s advantage over an older GLP-1 drug; the results appear in the STEP 8 report. Useful, but again a separate context.
How do the two compare across the evidence?
| Question | Tirzepatide | Semaglutide |
|---|---|---|
| Average weight loss, direct trial | Larger in the 2024 head-to-head | Smaller in the 2024 head-to-head |
| Mechanism | Acts on GIP and GLP-1 receptors | Acts on the GLP-1 receptor |
| Regain after stopping | Seen in SURMOUNT-4 | Seen in STEP 4 |
| Extra condition evidence | Obstructive sleep apnea trial | Broad cardiometabolic program |
What happens if treatment stops?
Both drugs are studied as ongoing therapy, not a short course, and the withdrawal data make the reason clear. SURMOUNT-4, published in 2023, kept some participants on tirzepatide and switched others to placebo after an initial period; those switched to placebo regained a substantial share of the weight they had lost, as shown in the SURMOUNT-4 maintenance trial. The pattern repeats with semaglutide. STEP 4, published in 2021, found that stopping led to regain while continuing preserved most of the loss; that result is in the STEP 4 report.
This matters more than the headline percentage. A drug that produces a slightly larger loss but that someone cannot afford or tolerate long term may leave them worse off than the alternative they can stay on. The sustainable choice usually beats the marginally stronger one.
Does the difference hold across different groups?
The tirzepatide evidence extends beyond the original obesity trials. SURMOUNT-CN, published in 2024, tested tirzepatide in Chinese adults with obesity and reported strong reductions in that population; the findings are in the SURMOUNT-CN trial. There is also a dedicated study of tirzepatide in people with obstructive sleep apnea and obesity, published in 2024, which found improvements in apnea measures alongside weight loss. That evidence appears in the sleep apnea trial, and it is a genuine reason some prescribers lean toward tirzepatide for patients with that condition.
What about cost, access, and compounded versions?
Weight loss on paper does not set what a person pays. Both brands list well above a thousand dollars a month, coverage for weight management is patchy, and the drug that fits a budget is often the one that gets taken consistently. Manufacturer self-pay programs and telehealth prescribing have widened the routes to both molecules. Some supervised telehealth practices, including Ro, Hims and Hers, Henry Meds, and FormBlends, publish flat monthly pricing for compounded versions, and for readers weighing that route it helps to read the full breakdown before assuming any advertised figure applies to them.
Compounded semaglutide and tirzepatide are not the same as the brands. They are prepared by compounding pharmacies and are not FDA-approved products, so they have not gone through the process that generated the trial evidence discussed here. The brand labels are the reference for approved use; the current details sit in the Zepbound prescribing information and the Mounjaro prescribing information. Compounded pricing can look attractive, but it trades regulatory assurance for a predictable cash price, and that trade belongs with a prescriber who knows the case rather than with a marketing page.
So which one should a person choose?
If the only goal is the largest average weight loss and both are affordable and tolerated, the direct trial points to tirzepatide. That is an honest read of the data. But the honest read also says the gap is smaller than the marketing suggests for many people, semaglutide has a deep track record, and side effects, cost, and coexisting conditions frequently outweigh a few percentage points. There is no single winner for everyone, and anyone told there is should ask harder questions.
Key takeaways
- The one direct trial favors tirzepatide for average weight loss, but the margin is modest for many people.
- Stacking SURMOUNT against STEP is not a valid comparison, since they enrolled different populations.
- Both drugs show meaningful regain after stopping, so they are studied as ongoing treatment.
- Tolerability, cost, and conditions like sleep apnea often matter more than the headline number.
- Compounded versions are not FDA-approved and are not equivalent to the brand medications.
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Frequently asked questions
Does tirzepatide beat semaglutide on weight loss?
In the one head-to-head trial, tirzepatide produced larger average weight loss than semaglutide over 72 weeks. Trial averages describe groups, not any single person, and individual response varies widely.
Are the SURMOUNT and STEP numbers directly comparable?
Not cleanly. SURMOUNT tested tirzepatide and STEP tested semaglutide in separate populations with different designs. Cross-trial numbers hint at a difference but do not prove one. The direct comparison came from a single randomized study.
Is more weight loss always the better choice?
No. Tolerability, cost, coverage, and other conditions like sleep apnea can matter more than the last few percentage points. The drug a person can actually stay on tends to win over time.
Does weight come back if the drug stops?
Trials of both molecules show meaningful regain after stopping. Maintenance studies treat these as ongoing therapies rather than short courses.
Is compounded tirzepatide or semaglutide the same as the brand?
No. Compounded versions are prepared by compounding pharmacies and are not FDA-approved products. They may contain the same active molecule but have not gone through the approval process behind the trial evidence.
