Tirzepatide lowered glycated haemoglobin in people with type 2 diabetes by 1.87 to 2.58 percentage points. These were the results of five phase three trials in the SURPASS programme, with more than 6200 people in total. In each of them tirzepatide did better than placebo, insulin or semaglutide. If you want to know exactly what was measured and how each comparison turned out, below you will find all the figures.
Why does tirzepatide act on blood sugar?
Tirzepatide stimulates two gut hormone receptors at once: GLP-1 and GIP. Both hormones are incretins, signals that boost insulin release after a meal. The strength of this action depends on the blood glucose level. That is why in SURPASS-1 tirzepatide used as the only drug did not cause a single episode of severe hypoglycaemia.
Tirzepatide is the active substance of the medicine Mounjaro, dispensed on prescription. The details of its action on both receptors are described in the guide on tirzepatide, GLP-1 and GIP.
What does glycated haemoglobin measure?
Glycated haemoglobin, HbA1c for short, shows the average blood sugar level over the last three months. It is given as a percentage. According to the US CDC, a result below 5.7 percent is normal, and 6.5 percent or more means diabetes. In the SURPASS trials the treatment target was a result below 7.0 percent.
In all SURPASS trials the main measure was the change in HbA1c from the start to the end of the trial. Alongside it, body weight, fasting glucose and the share of people who reached the treatment target were measured. Episodes of low blood sugar, or hypoglycaemia, were also counted.
What did the SURPASS-1 trial show?
In SURPASS-1, tirzepatide used as the only drug lowered HbA1c by 1.87 to 2.07 percentage points. The trial was published in 2021 in the Lancet. It included 478 people for whom diet and exercise were not enough. The average HbA1c at the start was 7.9 percent, and the trial lasted 40 weeks.
In the placebo group HbA1c rose by 0.04 points. The target of below 7 percent was reached by 87 to 92 percent of people on tirzepatide and 20 percent on placebo. A result below 5.7 percent, in the range of people without diabetes, was reached by 31 to 52 percent of participants. Body weight fell by 7.0 to 9.5 kg, and no severe hypoglycaemia was recorded.
Does tirzepatide work better than semaglutide?
Yes, in the head-to-head SURPASS-2 trial every dose of tirzepatide lowered HbA1c more than semaglutide 1 mg. The trial appeared in 2021 in the New England Journal of Medicine. It included 1879 people with an average HbA1c of 8.28 percent and an average weight of 93.7 kg. The trial lasted 40 weeks, and tirzepatide and semaglutide were given once a week.
| Result after 40 weeks | Tirzepatide 5 mg | Tirzepatide 10 mg | Tirzepatide 15 mg | Semaglutide 1 mg |
|---|---|---|---|---|
| Fall in HbA1c | 2.01 points | 2.24 points | 2.30 points | 1.86 points |
| Weight advantage over semaglutide | 1.9 kg | 3.6 kg | 5.5 kg | reference |
The differences in HbA1c were statistically significant at every tirzepatide dose. Nausea was reported by 17 to 22 percent of people on tirzepatide and 18 percent on semaglutide. Hypoglycaemia below 54 mg/dl was rare in both groups, from 0.2 to 1.7 percent.
How does tirzepatide compare with insulin?
In two trials tirzepatide lowered HbA1c more than long-acting insulin, and it also lowered body weight. In SURPASS-3 it was compared with insulin degludec in 1444 people over 52 weeks. Tirzepatide lowered HbA1c by 1.93 to 2.37 points, insulin by 1.34 points. Body weight fell on tirzepatide by 7.5 to 12.9 kg, while on insulin it rose by 2.3 kg.
In SURPASS-4, tirzepatide was compared with insulin glargine in 2002 people at high cardiovascular risk. After 52 weeks HbA1c fell by 2.43 points at 10 mg and by 2.58 points at 15 mg. On insulin the fall was 1.44 points. Hypoglycaemia was reported by 6 to 9 percent of people on tirzepatide and 19 percent on insulin.
Does tirzepatide help people already taking insulin?
Yes, in SURPASS-5 adding tirzepatide to insulin glargine lowered HbA1c by 2.11 to 2.40 points. In the placebo group, which also received insulin, the fall was 0.86 points. The trial was published in 2022 in JAMA. It included 475 people with an average HbA1c of 8.31 percent, treated for 40 weeks.
Body weight fell by 5.4 kg at 5 mg, 7.5 kg at 10 mg and 8.8 kg at 15 mg. In the placebo group it rose by 1.6 kg. The HbA1c target of below 7 percent was reached by 85 to 90 percent of people on tirzepatide and 34 percent on placebo.
How did the five SURPASS trials turn out in one table?
The table brings together the fall in HbA1c in the five main trials of the programme. All lasted 40 to 52 weeks and involved adults with type 2 diabetes.
| Trial | Number of people | Comparison | Fall in HbA1c on tirzepatide | Fall in HbA1c in the comparison group |
|---|---|---|---|---|
| SURPASS-1 | 478 | placebo | 1.87-2.07 points | rise of 0.04 points |
| SURPASS-2 | 1879 | semaglutide 1 mg | 2.01-2.30 points | 1.86 points |
| SURPASS-3 | 1444 | insulin degludec | 1.93-2.37 points | 1.34 points |
| SURPASS-4 | 2002 | insulin glargine | 2.43-2.58 points (10 and 15 mg) | 1.44 points |
| SURPASS-5 | 475 | placebo added to insulin | 2.11-2.40 points | 0.86 points |
What does tirzepatide do for the heart in people with diabetes?
In the largest heart trial, tirzepatide proved at least as safe for the heart as dulaglutide. The SURPASS-CVOT trial appeared in 2025 in the New England Journal of Medicine. It included 13,165 people with type 2 diabetes and atherosclerotic disease. Dulaglutide is an older GLP-1 drug with a proven protective effect on the heart.
Cardiovascular death, heart attack or stroke occurred in 12.2 percent of people on tirzepatide and 13.1 percent on dulaglutide. The result confirmed that tirzepatide is not worse than dulaglutide. The numerical advantage of tirzepatide did not, however, reach statistical significance. The effects of this group of drugs on the heart and kidneys are covered in more detail in the guide on semaglutide and tirzepatide for the heart, kidneys, sleep and liver.
Does tirzepatide protect against developing diabetes?
In the three-year part of SURMOUNT-1, tirzepatide clearly reduced the number of new cases of diabetes. It covered 1032 people with obesity and prediabetes. After 176 weeks, type 2 diabetes was diagnosed in 1.3 percent of people on tirzepatide and 13.3 percent on placebo. After 17 weeks without treatment, the figures were 2.4 and 13.7 percent.
How much does tirzepatide cost in the shop?
In the shop, tirzepatide comes in three versions. Tirzepatide 20 mg Bio-Peptide costs 200 EUR and is in stock. Tirzepatide 20 mg Genheal costs 200 EUR on backorder. Tirzepatide 40 mg Nouveaux in a pen costs 350 EUR and contains a ready-made solution.
All versions and the price per milligram are on the tirzepatide page. How research material differs from the medicine Mounjaro is explained in the guide on why semaglutide and tirzepatide are prescription-only. Diabetes treatment is run by a doctor, and the products in the shop are for laboratory research.
Frequently asked questions
How much does tirzepatide lower HbA1c?
In five SURPASS trials, tirzepatide lowered HbA1c by 1.87 to 2.58 percentage points over 40 to 52 weeks, depending on the dose and the trial.
Is tirzepatide better than semaglutide in diabetes?
In SURPASS-2 every dose of tirzepatide lowered HbA1c more than semaglutide 1 mg, by 2.01 to 2.30 points versus 1.86 points.
Does tirzepatide cause low blood sugar?
No severe hypoglycaemia was recorded in SURPASS-1. In SURPASS-4 hypoglycaemia was reported by 6 to 9 percent of people on tirzepatide and 19 percent on insulin glargine.
Is tirzepatide safe for the heart?
In SURPASS-CVOT with 13,165 people, cardiovascular death, heart attack or stroke occurred in 12.2 percent on tirzepatide and 13.1 percent on dulaglutide.
Can tirzepatide be combined with insulin?
In SURPASS-5 adding tirzepatide to insulin glargine lowered HbA1c by 2.11 to 2.40 points and body weight by 5.4 to 8.8 kg.
Sources
- Rosenstock J, Wysham C, Frías JP et al. Efficacy and safety of a novel dual GIP and GLP-1 receptor agonist tirzepatide in patients with type 2 diabetes (SURPASS-1): a double-blind, randomised, phase 3 trial. Lancet, 2021, 398(10295): 143-155. https://doi.org/10.1016/S0140-6736(21)01324-6
- Frías JP, Davies MJ, Rosenstock J et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes. New England Journal of Medicine, 2021, 385(6): 503-515. https://doi.org/10.1056/NEJMoa2107519
- Ludvik B, Giorgino F, Jódar E et al. Once-weekly tirzepatide versus once-daily insulin degludec as add-on to metformin with or without SGLT2 inhibitors in patients with type 2 diabetes (SURPASS-3). Lancet, 2021, 398(10300): 583-598. https://doi.org/10.1016/S0140-6736(21)01443-4
- Del Prato S, Kahn SE, Pavo I et al. Tirzepatide versus insulin glargine in type 2 diabetes and increased cardiovascular risk (SURPASS-4). Lancet, 2021, 398(10313): 1811-1824. https://doi.org/10.1016/S0140-6736(21)02188-7
- Dahl D, Onishi Y, Norwood P et al. Effect of Subcutaneous Tirzepatide vs Placebo Added to Titrated Insulin Glargine on Glycemic Control in Patients With Type 2 Diabetes: The SURPASS-5 Randomized Clinical Trial. JAMA, 2022, 327(6): 534-545. https://doi.org/10.1001/jama.2022.0078
- Nicholls SJ, Pavo I, Bhatt DL et al. Cardiovascular Outcomes with Tirzepatide versus Dulaglutide in Type 2 Diabetes. New England Journal of Medicine, 2025, 393(24): 2409-2420. https://doi.org/10.1056/NEJMoa2505928
- Jastreboff AM, le Roux CW, Stefanski A et al. Tirzepatide for Obesity Treatment and Diabetes Prevention. New England Journal of Medicine, 2025, 392(10): 958-971. https://doi.org/10.1056/NEJMoa2410819
- Centers for Disease Control and Prevention. A1C Test for Diabetes and Prediabetes. https://www.cdc.gov/diabetes/diabetes-testing/prediabetes-a1c-test.html