Research

The trials behind tirzepatide

Tirzepatide 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

4

Participants across them

5,839

Longest trial, in weeks

88

The trials in this corpus

• SURMOUNT-1

  20.9%of body weight lost at the top dose, against 3.1% on placebo

  At week 72 mean weight change was -15.0% on 5 mg, -19.5% on 10 mg and -20.9% on 15 mg, against -3.1% on placebo. In the 15 mg group 57% of participants lost 20% of body weight or more, against 3% on placebo.

  Participants

  2,539

  Weeks

  72

  Against

  Placebo

  Jastreboff AM, New England Journal of Medicine 2022 · PMID 35658024

• SURPASS-2

  2.30percentage points off HbA1c, against 1.86 on semaglutide

  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-4

  14.0%regained by those switched to placebo, against 5.5% lost on tirzepatide

  Between week 36 and week 88 weight changed by -5.5% on continued tirzepatide and by +14.0% on placebo, a difference of 19.4 percentage points. Participants had lost a mean 20.9% during the lead-in; 89.5% of those continuing held at least 80% of that loss, against 16.6% of those switched to placebo.

  Participants

  670

  Weeks

  88

  Against

  Placebo, by withdrawal of tirzepatide

  Aronne LJ, JAMA 2024 · PMID 38078870

• SURMOUNT-5

  20.2%of body weight lost, against 13.7% on semaglutide

  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 tirzepatide cause cancer? The rat data and the human dataThe boxed warning comes from rat thyroid tumors. In 13 tirzepatide trials of 13,761 people, cancer did not rise and no medullary thyroid cancer was seen.
• Tirzepatide weight loss results, week by weekWhat SURMOUNT-1, Study 1 in the Zepbound label, found at weeks 8, 12, 24 and 72: most of the weight came off in the first six months, then the loss slowed.

What they measured

3 of the 4 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.

The corpus at a glance