Research
The trials behind semaglutide
Semaglutide is one of the better-evidenced medications a reader of this site will encounter, and almost none of that evidence is about what the price index sells. This corpus separates the two.
Every trial below was located on PubMed and its PMID resolved before anything here was written. Each figure is reported with the comparator it was measured against, the number of weeks it took, and the number of participants it came from.
- Trials in this corpus
- 6
- Participants across them
- 6,933
- Longest trial, in weeks
- 72
The trials in this corpus
- STEP 1
14.9%mean body-weight change at 68 weeks, against 2.4% on placebo
Mean body weight changed by -14.9% on semaglutide against -2.4% on placebo, an estimated treatment difference of -12.4 percentage points. 86.4% of the semaglutide group lost at least 5% of body weight, against 31.5% on placebo.
- Participants
- 1,961
- Weeks
- 68
- Against
- Placebo, plus lifestyle intervention
Wilding JPH, New England Journal of Medicine 2021 · PMID 33567185
- STEP 4
+6.9%regained by those switched to placebo, against 7.9% lost on continued semaglutide
From week 20 to week 68 mean body weight changed by -7.9% with continued semaglutide against +6.9% after the switch to placebo, a difference of -14.8 percentage points. The 20-week run-in had itself produced a mean weight loss of 10.6%.
- Participants
- 803
- Weeks
- 68
- Against
- A switch to placebo after the run-in
Rubino D, JAMA 2021 · PMID 33755728
- SUSTAIN 7
6.5 kgof bodyweight lost on semaglutide 1.0 mg, against 3.0 kg on dulaglutide 1.5 mg
HbA1c fell by 1.8 percentage points on semaglutide 1.0 mg against 1.4 on dulaglutide 1.5 mg. Bodyweight fell by 6.5 kg against 3.0 kg on the higher doses, and by 4.6 kg against 2.3 kg on the lower pair.
- Participants
- 1,201
- Weeks
- 40
- Against
- Dulaglutide at 0.75 mg and 1.5 mg once weekly
Pratley RE, The Lancet Diabetes & Endocrinology 2018 · PMID 29397376
- STEP 8
15.8%mean weight change at 68 weeks, against 6.4% on liraglutide 3.0 mg
Mean weight change was -15.8% on semaglutide against -6.4% on liraglutide, a difference of -9.4 percentage points; -1.9% on pooled placebo.
- Participants
- 338
- Weeks
- 68
- Against
- Liraglutide 3.0 mg daily (and pooled placebo)
Rubino DM, JAMA 2022 · PMID 35015037
- SURPASS-2
1.86percentage points off HbA1c on semaglutide 1 mg, against 2.30 on tirzepatide 15 mg
Glycated hemoglobin fell by 2.01, 2.24 and 2.30 percentage points on tirzepatide 5 mg, 10 mg and 15 mg, against 1.86 points on semaglutide 1 mg. Tirzepatide was noninferior and superior at every dose. Weight fell further on tirzepatide, by an estimated 1.9 kg, 3.6 kg and 5.5 kg respectively.
- Participants
- 1,879
- Weeks
- 40
- Against
- Semaglutide 1 mg once weekly
Frías JP, New England Journal of Medicine 2021 · PMID 34170647
- SURMOUNT-5
13.7%of body weight lost, against 20.2% on tirzepatide
At week 72 weight fell by 20.2% on tirzepatide and 13.7% on semaglutide. Waist circumference fell by 18.4 cm and 13.0 cm respectively.
- Participants
- 751
- Weeks
- 72
- Against
- Semaglutide at 1.7 mg or 2.4 mg once weekly
Aronne LJ, New England Journal of Medicine 2025 · PMID 40353578
More from the research
- Does semaglutide cause cancer? What the evidence showsThe boxed warning comes from rodent thyroid tumors of undetermined human relevance. In SELECT, cancers were reported by 4.8% on semaglutide, 4.7% on placebo.
- Semaglutide long-term side effectsWegovy's longest trial followed 17,604 adults for 39.8 months on average. More quit for side effects (16.6% vs 8.2%) and gallbladder problems rose.
- Semaglutide results by monthWeight loss on semaglutide showed from the first check at week 4, bottomed out at week 60 in STEP 1, and averaged 14.9% at 68 weeks against 2.4% on placebo.
What they measured
5 of the 6 trials report weight change per study arm. Each chart below draws only figures that appear in that trial’s own published abstract, beside the comparator it was measured against — which is the part most coverage drops.
Filled bar is semaglutide; the outlined bar is placebo, plus lifestyle intervention. Read from the published abstract, PMID 33567185.
Filled bar is semaglutide; the outlined bar is a switch to placebo after the run-in. Read from the published abstract, PMID 33755728.
Filled bar is semaglutide; the outlined bar is dulaglutide at 0.75 mg and 1.5 mg once weekly. Read from the published abstract, PMID 29397376.
Filled bar is semaglutide; the outlined bar is liraglutide 3.0 mg daily (and pooled placebo). Read from the published abstract, PMID 35015037.
Filled bar is semaglutide; the outlined bar is semaglutide at 1.7 mg or 2.4 mg once weekly. Read from the published abstract, PMID 40353578.
The corpus at a glance
| Trial | Compared against | Participants | Weeks |
|---|---|---|---|
| STEP 1 | Placebo, plus lifestyle intervention | 1,961 | 68 |
| STEP 4 | A switch to placebo after the run-in | 803 | 68 |
| SUSTAIN 7 | Dulaglutide at 0.75 mg and 1.5 mg once weekly | 1,201 | 40 |
| STEP 8 | Liraglutide 3.0 mg daily (and pooled placebo) | 338 | 68 |
| SURPASS-2 | Semaglutide 1 mg once weekly | 1,879 | 40 |
| SURMOUNT-5 | Semaglutide at 1.7 mg or 2.4 mg once weekly | 751 | 72 |
References
- Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine. 2021;384(11):989-1002. PMID: 33567185. NCT03548935.
- Rubino D, et al. 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. 2021;325(14):1414-1425. PMID: 33755728. NCT03548987.
- Pratley RE, et al. Semaglutide versus dulaglutide once weekly in patients with type 2 diabetes (SUSTAIN 7): a randomised, open-label, phase 3b trial. The Lancet Diabetes & Endocrinology. 2018;6(4):275-286. PMID: 29397376. NCT02648204.
- Rubino DM, et al. Effect of Weekly Subcutaneous Semaglutide vs Daily Liraglutide on Body Weight in Adults With Overweight or Obesity Without Diabetes: The STEP 8 Randomized Clinical Trial. JAMA. 2022;327(2):138-150. PMID: 35015037. NCT04074161.
- Frías JP, et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes. New England Journal of Medicine. 2021;385(6):503-515. PMID: 34170647. NCT03987919.
- Aronne LJ, et al. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity. New England Journal of Medicine. 2025;393(1):26-36. PMID: 40353578. NCT05822830.