In people with type 2 diabetes, semaglutide lowered glycated haemoglobin by 1.2 to 2.2 points, depending on the dose and the trial. In the SUSTAIN programme it did better than sitagliptin, insulin glargine, dulaglutide and canagliflozin, four commonly used medicines. In SUSTAIN 6 it reduced the risk of heart attack, stroke or cardiovascular death by 26 percent. Below we collect the results of all the most important SUSTAIN trials in one place.
What is the SUSTAIN trial programme?
SUSTAIN is a series of clinical trials of semaglutide in type 2 diabetes, run by the maker of Ozempic. It tested semaglutide at doses of 0.5, 1 and 2 mg once a week. It was compared with placebo and with other diabetes medicines, at different stages of the disease.
The main measure was glycated haemoglobin, or HbA1c. This is the average blood sugar level over the last two to three months, given as a percentage. In people with type 2 diabetes in these trials it was usually around 8 percent at the start.
What did SUSTAIN 1 show?
SUSTAIN 1 tested semaglutide as the only medicine in people who had so far been treated only with diet and exercise. It included 388 people with an average glycated haemoglobin of 8.05 percent. The results were published in 2017 in The Lancet Diabetes and Endocrinology.
| SUSTAIN 1, after 30 weeks | Semaglutide 0.5 mg | Semaglutide 1 mg | Placebo |
|---|---|---|---|
| Fall in HbA1c | 1.45 points | 1.55 points | 0.02 points |
| Weight loss | 3.73 kg | 4.53 kg | 0.98 kg |
| Nausea | 20 percent of people | 24 percent of people | 8 percent of people |
Between 11 and 13 percent of people stopped treatment, similarly in each group. There were no deaths in any group, and most side effects were mild or moderate.
How did semaglutide compare with other medicines?
In direct comparisons semaglutide lowered blood sugar and body weight more than each of the four medicines tested. The table collects the results at the 1 mg dose.
| Trial | Comparator | Duration | Fall in HbA1c: semaglutide 1 mg vs comparator | Body weight: semaglutide 1 mg vs comparator |
|---|---|---|---|---|
| SUSTAIN 2 | sitagliptin | 56 weeks | 1.6 vs 0.5 points | -6.1 vs -1.9 kg |
| SUSTAIN 4 | insulin glargine | 30 weeks | 1.64 vs 0.83 points | -5.17 vs +1.15 kg |
| SUSTAIN 7 | dulaglutide 1.5 mg | 40 weeks | 1.8 vs 1.4 points | -6.5 vs -3.0 kg |
| SUSTAIN 8 | canagliflozin | 52 weeks | 0.49 points more | 1.06 kg more |
On insulin glargine body weight went up, while on semaglutide it went down. In SUSTAIN 4 blood sugar falling too low was also less frequent on semaglutide: 6 percent of people at 1 mg against 11 percent on insulin.
In SUSTAIN 9, adding semaglutide 1 mg to a medicine from the SGLT-2 inhibitor group lowered glycated haemoglobin by 1.42 points more than placebo. Body weight fell by 3.81 kg more. Medicines from both groups can therefore be combined.
What did SUSTAIN 6 show about the heart?
SUSTAIN 6 tested how semaglutide affects the heart in people with diabetes and high cardiovascular risk. It included 3297 people, 83 percent of whom already had heart disease, kidney disease or both. The trial lasted 104 weeks, and the results were published in 2016 in the New England Journal of Medicine.
| SUSTAIN 6, after 104 weeks | Semaglutide | Placebo |
|---|---|---|
| Heart attack, stroke or cardiovascular death | 6.6 percent of people | 8.9 percent of people |
| Non-fatal heart attack | 2.9 percent of people | 3.9 percent of people |
| Non-fatal stroke | 1.6 percent of people | 2.7 percent of people |
The risk of the main endpoint was 26 percent lower than on placebo. New or worsening kidney disease also appeared less often. The rate of cardiovascular deaths was similar in both groups.
In the same trial, complications of diabetic retinopathy, a disease of the retina of the eye, were more frequent. People with retinopathy should therefore have their eyes checked regularly by an eye doctor during treatment.
What does the 2 mg dose add?
The 2 mg dose lowers blood sugar more strongly than 1 mg. In SUSTAIN FORTE, glycated haemoglobin fell after 40 weeks by 2.2 points at 2 mg and by 1.9 points at 1 mg. Body weight fell by 6.9 kg against 6.0 kg, and stomach complaints were reported by 34 against 31 percent of people.
The SUSTAIN OPTIMIZE trial from July 2026 tested the 2 mg dose in 573 people treated with insulin. Semaglutide added to a reduced insulin dose lowered glycated haemoglobin by 0.74 points more than insulin alone at an increased dose. Body weight was 8.5 kg lower, and severe falls in blood sugar occurred less than half as often.
Higher doses were also tested for people with diabetes and obesity. In STEP 2 the 2.4 mg dose lowered body weight by 9.6 percent after 68 weeks. All doses and their results are compared in the guide on semaglutide doses in trials.
How does semaglutide compare with tirzepatide?
In the direct comparison SURPASS-2, tirzepatide lowered blood sugar more strongly than semaglutide 1 mg. Glycated haemoglobin fell by 2.01 to 2.30 points on tirzepatide and by 1.86 points on semaglutide. The details of this and other trials are described in the guide on tirzepatide and the SURPASS trials.
Semaglutide, on the other hand, has data from SUSTAIN 6 on reducing cardiovascular risk in people with diabetes. The effect of both molecules on the heart, kidneys and liver is collected in the guide semaglutide and tirzepatide beyond weight loss.
Where to buy semaglutide?
The shop offers semaglutide 3 mg Bio-Peptide for 90 EUR, in stock. At a dose of 1 mg a week one vial lasts three weeks, so a week costs about 30 EUR. All information about the molecule is collected on the semaglutide page.
The products in the shop are material for laboratory research, not the medicine Ozempic. Diabetes treatment is managed by a doctor, and no research material replaces it. The difference is described in the guide why semaglutide and tirzepatide are prescription only.
Frequently asked questions
How much does semaglutide lower blood sugar in type 2 diabetes?
In the SUSTAIN trials glycated haemoglobin fell by 1.2 to 2.2 points, depending on the dose and the trial. The 2 mg dose gave 2.2 points in SUSTAIN FORTE.
Does semaglutide work better than other diabetes medicines?
In SUSTAIN 2, 4, 7 and 8 it lowered blood sugar and body weight more than sitagliptin, insulin glargine, dulaglutide and canagliflozin.
Does semaglutide protect the heart in diabetes?
In SUSTAIN 6, heart attack, stroke or cardiovascular death occurred in 6.6 percent of people on semaglutide and 8.9 percent on placebo, so the risk was 26 percent lower.
Do people with diabetes lose weight on semaglutide?
Yes, at the 1 mg dose by 4.5 to 6.5 kg in the SUSTAIN trials. At the 2.4 mg dose in STEP 2 body weight fell by 9.6 percent.
Can semaglutide be combined with other diabetes medicines?
In trials it was combined with metformin, SGLT-2 inhibitors and insulin. In SUSTAIN 9, adding it to an SGLT-2 inhibitor lowered HbA1c by 1.42 points more than placebo.
Sources
- Sorli C, Harashima SI, Tsoukas GM et al. Efficacy and safety of once-weekly semaglutide monotherapy versus placebo in patients with type 2 diabetes (SUSTAIN 1). The Lancet Diabetes and Endocrinology, 2017, 5(4): 251-260. https://doi.org/10.1016/S2213-8587(17)30013-X
- Ahrén B, Masmiquel L, Kumar H et al. Efficacy and safety of once-weekly semaglutide versus once-daily sitagliptin as an add-on to metformin, thiazolidinediones, or both (SUSTAIN 2). The Lancet Diabetes and Endocrinology, 2017, 5(5): 341-354. https://doi.org/10.1016/S2213-8587(17)30092-X
- Aroda VR, Bain SC, Cariou B et al. Efficacy and safety of once-weekly semaglutide versus once-daily insulin glargine as add-on to metformin in insulin-naive patients with type 2 diabetes (SUSTAIN 4). The Lancet Diabetes and Endocrinology, 2017, 5(5): 355-366. https://doi.org/10.1016/S2213-8587(17)30085-2
- Marso SP, Bain SC, Consoli A et al. Semaglutide and Cardiovascular Outcomes in Patients with Type 2 Diabetes. New England Journal of Medicine, 2016, 375(19): 1834-1844. https://doi.org/10.1056/NEJMoa1607141
- Pratley RE, Aroda VR, Lingvay I et al. Semaglutide versus dulaglutide once weekly in patients with type 2 diabetes (SUSTAIN 7). The Lancet Diabetes and Endocrinology, 2018, 6(4): 275-286. https://doi.org/10.1016/S2213-8587(18)30024-X
- Lingvay I, Catarig AM, Frias JP et al. Efficacy and safety of once-weekly semaglutide versus daily canagliflozin as add-on to metformin in patients with type 2 diabetes (SUSTAIN 8). The Lancet Diabetes and Endocrinology, 2019, 7(11): 834-844. https://doi.org/10.1016/S2213-8587(19)30311-0
- Zinman B, Bhosekar V, Busch R et al. Semaglutide once weekly as add-on to SGLT-2 inhibitor therapy in type 2 diabetes (SUSTAIN 9). The Lancet Diabetes and Endocrinology, 2019, 7(5): 356-367. https://doi.org/10.1016/S2213-8587(19)30066-X
- Frías JP, Auerbach P, Bajaj HS et al. Efficacy and safety of once-weekly semaglutide 2.0 mg versus 1.0 mg in patients with type 2 diabetes (SUSTAIN FORTE). The Lancet Diabetes and Endocrinology, 2021, 9(9): 563-574. https://doi.org/10.1016/S2213-8587(21)00174-1
- Rodbard HW, Irace C, Lobo J et al. Efficacy and Safety of Once-Weekly Semaglutide 2.0 mg as an Add-On to Dose-Reduced Insulin Glargine versus Dose-Titrated Insulin Glargine in People With Type 2 Diabetes and Overweight (SUSTAIN OPTIMIZE). Diabetes, Obesity and Metabolism, 2026, 28(10): 9304-9316. https://doi.org/10.1111/dom.71132
- Davies M, Færch L, Jeppesen OK et al. Semaglutide 2.4 mg once a week in adults with overweight or obesity, and type 2 diabetes (STEP 2). The Lancet, 2021, 397(10278): 971-984. https://doi.org/10.1016/S0140-6736(21)00213-0