What the SURPASS trial programme found about tirzepatide

Where the SURPASS programme started and why it matters

Eli Lilly designed the SURPASS trials to test tirzepatide across the full spectrum of type 2 diabetes management: as a first injectable therapy, against semaglutide, against insulin, and in people with cardiovascular disease or kidney disease. The trial IDs run from SURPASS-1 through SURPASS-6 (with SURPASS-CVOT sitting outside the numbered sequence as a cardiovascular outcomes trial). Together they recruited tens of thousands of adults with type 2 diabetes across multiple countries. You can read the overview of the broader SURPASS study design if you want the programme architecture before getting into individual results.

The primary endpoint across most trials was reduction in HbA1c, the standard measure of longer-term blood glucose control. Body weight was a key secondary endpoint in every trial, which is part of why SURPASS data directly informed the decision to run the SURMOUNT programme in people with obesity who did not have diabetes. The SURPASS trials, in other words, were not just a diabetes story.

NICE's appraisal of tirzepatide drew on this clinical programme when evaluating tirzepatide's evidence base. The NICE technology appraisal TA1026 (published December 2024, updated September 2025) references the depth of randomised trial evidence as part of its recommendation for tirzepatide in weight management.

What the individual SURPASS trials found

SURPASS-1 tested tirzepatide against placebo in adults whose diabetes was managed by diet and exercise alone. At 40 weeks, HbA1c reductions ranged from around 1.9 to 2.1 percentage points depending on dose, with placebo producing a modest 0.04-point reduction. Body weight fell by roughly 7–9.5kg across the tirzepatide arms. SURPASS-1's full results give a clearer picture of what those numbers mean in practice.

SURPASS-2 was arguably the most consequential trial for the medicine's profile: it put tirzepatide head-to-head against semaglutide 1mg (Ozempic, licensed for type 2 diabetes) over 40 weeks. Tirzepatide at all three doses produced greater HbA1c reductions and greater weight loss than semaglutide 1mg. The SURPASS-2 comparison page details those figures and their clinical context. Published in the New England Journal of Medicine, this trial drew significant attention from both diabetes specialists and the wider medical press.

SURPASS-3 compared tirzepatide with insulin degludec; SURPASS-4 focused on high cardiovascular risk populations against insulin glargine. In both, tirzepatide produced non-inferior or superior glucose control alongside meaningful weight loss. SURPASS-3's insulin comparison is worth reading if you are specifically curious about how tirzepatide stacks up against basal insulin regimens.

Across the programme, the higher doses (10mg and 15mg) generally produced the largest effects, with gastrointestinal side effects (nausea, diarrhoea, reduced appetite) most common after starting or after a dose step-up. These typically settled within days to a couple of weeks.

How SURPASS connects to the weight-management evidence

The consistent body-weight reductions seen in SURPASS prompted the SURMOUNT programme, which enrolled adults with obesity rather than primarily diabetes. SURMOUNT-1, published in the New England Journal of Medicine and involving 2,539 adults, found average weight loss of around 20–21% at the 15mg dose over 72 weeks, making tirzepatide the basis for Mounjaro's weight-management licence in the UK. The tirzepatide surpass trials fed directly into that trajectory: without the SURPASS safety and efficacy data, SURMOUNT would not have had the foundation to build on.

For a detailed look at how the weight-management trial results differ from the diabetes programme, the SURPASS evidence summary sets out the distinction clearly. And if you are weighing tirzepatide against other options, the weight-loss treatment overview covers what is currently licensed in the UK.

One practical note: a consultation with a prescriber looks at far more than trial averages. What participants achieved in a controlled trial over 72 weeks, with regular contact and lifestyle support, reflects conditions most people's everyday lives do not perfectly replicate. That is not a reason to discount the evidence, it is a reason to take the clinical conversation seriously.

From trial data to a treatment decision

Knowing the SURPASS results is useful context. It tells you that tirzepatide's evidence base is broad, peer-reviewed, and includes direct comparisons with established medicines. What it cannot tell you is whether tirzepatide is right for you specifically. The SmPC sets out licensed indications and contraindications; in practice, a GPhC-registered prescriber reviews your medical history, current medicines, and BMI before any prescription is written. There are no shortcuts to that step, and no responsible pharmacy would offer one.

Lilly's pricing decisions have also shifted the cost landscape, the Eli Lilly Mounjaro UK price increase page explains what changed in September 2025 and what typical private pricing looks like now. Cost is a real consideration, but the trial data makes one thing plain: the clinical scrutiny behind tirzepatide is substantial. Cheap supply from unverified sources carries none of that assurance.

If the evidence has answered your questions about what tirzepatide has been shown to do, the next step is finding out whether it is suitable for you. Speak to our prescribers through a free consultation at our weight-loss treatments page.