As of: November 7, 2026 · Sources: New England Journal of Medicine
Semaglutide is a GLP-1 receptor agonist from Novo Nordisk and one of the best-studied drugs in its class. In the STEP 1 study, overweight or obese adults receiving 2.4 mg once weekly lost an average of 14.9% of their body weight after 68 weeks, compared to 2.4% with placebo [1]. Semaglutide is approved under the brand names Ozempic® and Rybelsus® for the treatment of type 2 diabetes and as Wegovy® for weight loss.
How does Semaglutide work?
Semaglutide mimics the gut hormone GLP-1 and binds to its receptor:
- Insulin secretion: Promotes glucose-dependent insulin release from the beta cells of the pancreas.
- Glucagon inhibition: It suppresses glucagon release and thus further stabilizes blood sugar.
- Gastric emptying: It slows down gastric emptying and thus prolongs the feeling of satiety.
- Brain: It acts on hunger and satiety centers in the hypothalamus and reduces food intake.
With a half-life of about one week, Semaglutide is designed for administration once a week.
What do the studies on Semaglutide show?
STEP 1 study (2021)
STEP 1 studied 1,961 overweight or obese adults without diabetes over 68 weeks, in addition to a lifestyle intervention [1]. Body weight decreased by an average of 14.9% in the Semaglutide group and by 2.4% in the placebo group. A reduction of at least 15% was achieved by 50.5% of participants in the Semaglutide group and by 4.9% in the placebo group.
Cardiovascular study SELECT (2023)
SELECT studied 17,604 adults aged 45 years and older with existing cardiovascular disease and overweight, but without diabetes [2]. Over an average of 39.8 months, cardiovascular death, myocardial infarction, or stroke occurred in 6.5% of participants taking Semaglutide, compared to 8.0% in the placebo group. This corresponds to a 20% lower risk.
Direct comparison with Tirzepatide: SURMOUNT-5 (2025)
In the SURMOUNT-5 trial, 751 adults with obesity without diabetes received either Semaglutide or Tirzepatide at the highest tolerated dose for 72 weeks [3]. Body weight decreased by 13.7% with Semaglutide and by 20.2% with Tirzepatide.
What side effects were observed?
Nausea and diarrhea were the most common side effects. They were mostly transient, mild to moderate, and resolved over time [1]. In the STEP 1 study, 4.5% of participants discontinued treatment due to gastrointestinal disturbances in the Semaglutide group, compared to 0.8% in the placebo group [1].
How does Semaglutide differ from Tirzepatide and Retatrutide?
Semaglutide acts only on the GLP-1 receptor and is the longest-available drug in this class, with correspondingly extensive long-term data. Tirzepatide and Retatrutide activate additional receptors. The table shows the main results of the respective registration and Phase 3 studies, evaluated across all participants:
| Active ingredient | Receptors | Average weight change | Study | Status |
|---|---|---|---|---|
| Semaglutide | GLP-1 | -14.9% after 68 weeks | STEP 1 [1] | approved |
| Tirzepatide | GLP-1, GIP | -20.9% after 72 weeks (15 mg) | SURMOUNT-1 [4] | approved |
| Retatrutide | GLP-1, GIP, Glucagon | -25.0% after 80 weeks (12 mg) | TRIUMPH-1 [5] | not approved yet |
The studies are not directly comparable because they differ in duration, dosage, and participants.
A detailed comparison of all three active ingredients.
Storage and shelf life of Semaglutide
Semaglutide is supplied as a lyophilized (freeze-dried) powder. Dry, light-protected storage at 2–8 °C is recommended. After dissolving in BAC water (bacteriostatic water), the solution should be refrigerated and used within 4 weeks.
All details are in the storage instructions.
Where can I buy Semaglutide?
Reta24 offers Semaglutide as a research peptide in strengths of 5 mg and 10 mg. Each batch is tested by HPLC for a purity of at least 98.9%. Shipping is from Germany.
View all dosages and current prices of Semaglutide.
Sources
- Wilding JPH, Batterham RL, Calanna S, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med 2021;384:989–1002. doi:10.1056/NEJMoa2032183
- Lincoff AM, Brown-Frandsen K, Colhoun HM, et al. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes. N Engl J Med 2023;389:2221–2232. doi:10.1056/NEJMoa2307563
- Aronne LJ, Horn DB, le Roux CW, et al. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity. N Engl J Med 2025;393:26–36. doi:10.1056/NEJMoa2416394
- Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med 2022;387:205–216. doi:10.1056/NEJMoa2206038
- Jastreboff AM, Kaplan LM, Davies MJ, et al. Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity. N Engl J Med 2026;395:1781–1793. doi:10.1056/NEJMoa2604169
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