The semaglutide dosage STEP-1 studied was 2.4 mg once weekly, and it took 16 weeks of stepped escalation to reach it. The 2.4 mg you see quoted is where that trial finished, not where it started. We treat the schedule as the answer, not the number.
The short version
STEP-1 used 2.4 mg once weekly over 68 weeks, reached by a four-step climb from 0.25 mg: 0.25, then 0.5, 1.0, 1.7 and 2.4, each held four weeks. That's 16 weeks to target. Mean weight reduction was about 14.9% against roughly 2.4% on placebo.
Semaglutide is the molecule that set the benchmark. Before STEP-1, the obesity pharmacotherapy ceiling sat well under 10%. STEP-1 made 15% the number to beat, and everything since has been measured against it: tirzepatide's 20.9%, retatrutide's Phase 2 24.2%.
What is the semaglutide escalation schedule?
Semaglutide climbs in four steps over 16 weeks: 0.25 mg, 0.5 mg, 1.0 mg, 1.7 mg, then 2.4 mg weekly, each step held four weeks. Here's the week-by-week schedule STEP-1 ran.
| Week | Dose | Note |
|---|---|---|
| 1–4 | 0.25 mg weekly | Tolerability step |
| 5–8 | 0.5 mg weekly | |
| 9–12 | 1.0 mg weekly | Around the Ozempic diabetes range |
| 13–16 | 1.7 mg weekly | |
| 17+ | 2.4 mg weekly | Target dose, held for the rest of the trial |
Four weeks per step, the same as tirzepatide and retatrutide. Sixteen weeks of a 68-week trial spent below target is a large fraction, and it's part of why cross-trial comparisons of “time to result” are harder than they look.
What did 2.4 mg of semaglutide produce?
Wilding and colleagues randomized 1,961 adults with overweight or obesity to semaglutide 2.4 mg weekly or placebo, both with lifestyle intervention, over 68 weeks. Mean body-weight reduction was approximately 14.9% versus about 2.4% on placebo.
Semaglutide also holds something no other compound in this class has: the SELECT trial, the only published demonstration of cardiovascular event reduction in the class.
Tirzepatide's CV outcome trials are pending. Retatrutide has a heart-rate signal and no outcome data at all. So if you're asking which of these has the best evidence rather than the biggest number, we'd point at semaglutide.
GLP1-S (semaglutide)
The GLP-1 analog reference compound behind the STEP trial literature. Research use only — supplied with a batch-matched certificate of analysis.
How do Ozempic and Wegovy doses differ?
Ozempic and Wegovy are the same semaglutide molecule with different indications and different top doses. Ozempic is approved for type 2 diabetes. Wegovy is approved for weight management and carries the 2.4 mg weekly top dose STEP-1 studied.
The distinction confuses a lot of search traffic, but it's just labeling around one active ingredient.
Semaglutide is also the compound at the center of the 503A compounding controversy. It's an approved active ingredient, which is exactly what made compounded versions legally possible during the shortage and legally fraught once it ended. We'd read that history before you buy semaglutide anywhere.
For sourcing, see where to buy semaglutide. The head-to-head covers how the two compare on more than weight.
Frequently asked questions
What is the semaglutide dose for weight loss?
STEP-1 used 2.4 mg once weekly, reached through a 16-week escalation: 0.25 mg for four weeks, then 0.5, 1.0, 1.7 and finally 2.4 mg, each held for four weeks.
What is the starting dose of semaglutide?
0.25 mg once weekly for the first four weeks. Like every opening dose in this class, semaglutide's is a tolerability step rather than a therapeutic one, far below the dose that produced the trial result.
How much weight did semaglutide produce in STEP-1?
Mean body-weight reduction of about 14.9% at 68 weeks on 2.4 mg weekly, against roughly 2.4% on placebo. That result established the 15% ceiling that tirzepatide and retatrutide were subsequently measured against.
How long does semaglutide escalation take?
Sixteen weeks to reach 2.4 mg, in four four-week steps. Nearly a quarter of the 68-week semaglutide trial went on titration.
What is the difference between Ozempic and Wegovy dosing?
Same molecule, different indications, different top doses. Ozempic is the type 2 diabetes product. Wegovy is the weight-management product, carrying the 2.4 mg weekly dose STEP-1 studied. So the 14.9% belongs to that schedule, not to any dose you'd find on the diabetes label.
GLP1-S (semaglutide)
Research-use-only material, sold by the vial with batch documentation. Check the certificate of analysis against the batch you receive.
What to know now
- STEP-1 targeted 2.4 mg once weekly. The trial ran 68 weeks, so most of it was spent at the target dose.
- Escalation took 16 weeks. Four steps — 0.25, 0.5, 1.0, 1.7 then 2.4 mg — each held for four weeks.
- Mean weight reduction was about 14.9%. Placebo reached roughly 2.4% over the same period.
- The early steps are not treatment doses. The first weeks exist to reach 2.4 mg, not to produce the headline result.
- Ozempic and Wegovy carry different doses. The 14.9% figure belongs to the 2.4 mg schedule, so lower doses do not inherit it.
References
- Wilding, J. P. H., Batterham, R. L., Calanna, S., et al. (2021). Once-weekly semaglutide in adults with overweight or obesity (STEP-1). New England Journal of Medicine, 384(11), 989–1002. https://doi.org/10.1056/NEJMoa2032183
- Lincoff, A. M., Brown-Frandsen, K., Colhoun, H. M., et al. (2023). Semaglutide and cardiovascular outcomes in obesity without diabetes. New England Journal of Medicine, 389(24), 2221–2232. https://doi.org/10.1056/NEJMoa2307563
- Rubino, D., Abrahamsson, N., Davies, M., et al. (2021). Effect of continued weekly subcutaneous semaglutide vs placebo on weight loss maintenance in adults with overweight or obesity: The STEP 4 randomized clinical trial. JAMA, 325(14), 1414–1425. https://doi.org/10.1001/jama.2021.3224
- Jastreboff, A. M., Aronne, L. J., Ahmad, N. N., et al. (2022). Tirzepatide once weekly for the treatment of obesity. New England Journal of Medicine, 387(3), 205–216. https://doi.org/10.1056/NEJMoa2206038