Semaglutide vs Tirzepatide: What the Research Compares

Semaglutide and tirzepatide are prescription medicines used under the care of a licensed clinician, and both have been studied in large randomized trials in type 2 diabetes and in obesity. Unlike many peptide comparisons, this pairing has been examined in direct head-to-head randomized trials, so the strongest comparative evidence does not depend on indirect inference alone. This page summarises what the published trials, meta-analyses and observational analyses reported, describes the pharmacologic class and mechanism of each medicine, and sets out their regulatory status. This page is for educational purposes only and is not medical advice; consult a licensed physician about any medical condition, medicine or treatment decision.

Head-to-Head Randomized Trials

Two randomized trials have compared tirzepatide with semaglutide directly, one in adults with type 2 diabetes and one in adults with obesity who did not have diabetes. Both were open-label, both ran for extended treatment periods, and both reported gastrointestinal events as the most frequent adverse events in each arm (SURPASS-2) (SURMOUNT-5).

SURPASS-2: type 2 diabetes

SURPASS-2 was an open-label, 40 week randomized trial in adults with type 2 diabetes that was inadequately controlled on metformin, and the study randomly assigned participants to three dose levels of once weekly tirzepatide or to once weekly semaglutide, with mean change in glycated hemoglobin from baseline to week 40 as the primary endpoint (NEJM, 2021). Researchers reported mean HbA1c reductions of 2.01, 2.24 and 2.30 percentage points across the three tirzepatide groups compared with 1.86 percentage points in the semaglutide group, and tirzepatide met the prespecified noninferiority criterion for the primary endpoint (NEJM, 2021). The same publication reported mean body weight reductions of 7.6, 9.3 and 11.2 kg across the tirzepatide groups and 5.7 kg in the semaglutide group (NEJM, 2021).

An important design feature discussed in the literature is that the semaglutide comparator in SURPASS-2 was the once weekly dose studied for glycemic control in type 2 diabetes rather than the higher dose later studied for weight management, a point reflected in the dose columns of the design table below (NEJM, 2021) (NEJM, 2025).

SURMOUNT-5: obesity without diabetes

SURMOUNT-5 was an open-label, 72 week randomized trial in adults with obesity who did not have type 2 diabetes, comparing once weekly tirzepatide with once weekly semaglutide, each titrated to a maximum tolerated dose, with percentage change in body weight from baseline to week 72 as the primary endpoint (NEJM, 2025). The study reported a least squares mean weight change of 20.2 percent in the tirzepatide group and 13.7 percent in the semaglutide group at week 72 (NEJM, 2025). Researchers reported that the most common adverse events in both groups were gastrointestinal and were mostly mild to moderate in severity (NEJM, 2025).

Design of the two head-to-head trials

The dose levels in this table appear only as a record of how the published trials were designed. Any question about dosing belongs with a prescribing clinician.

Comparative Evidence Beyond the Two Trials

Several systematic reviews and meta-analyses have pooled randomized data from the separate development programmes of each medicine and from the head-to-head trials. A network meta-analysis of subcutaneous tirzepatide versus semaglutide in adults with type 2 diabetes pooled randomized controlled trials and reported comparative estimates for HbA1c change and body weight change across the dose levels studied (Diabetologia, 2024). A network meta-analysis of GLP-1 receptor agonists and dual agonists for weight loss compared agents across randomized trials and reported relative weight change estimates for the included medicines (Diabetes Obesity and Metabolism, 2026).

A meta-analysis restricted to randomized trials of at least 20 weeks compared tirzepatide with placebo or with GLP-1 receptor agonists in adults with obesity or overweight and reported pooled weight loss estimates for each comparison (Journal of Obesity, 2025). A broader systematic review and meta-analysis of pharmacological treatments for obesity in adults pooled randomized trials across many drug classes and reported efficacy and safety estimates, including for agents in this class (Nature Medicine, 2025).

Observational research has also compared the two medicines in routine clinical care. A matched cohort analysis of adults with overweight or obesity treated with semaglutide or tirzepatide reported on-treatment weight change at multiple time points and on the frequency of gastrointestinal adverse events in each group (JAMA Internal Medicine, 2024). Observational designs of this type can reflect everyday prescribing patterns, although the authors of such analyses typically note that residual confounding and differences in dose escalation between groups limit causal interpretation (JAMA Internal Medicine, 2024).

Cardiovascular and heart failure outcomes

Comparative outcome data outside weight and glycemia are more limited. A real world analysis known as STEER examined cardiovascular outcomes among people with overweight or obesity treated with semaglutide or tirzepatide and reported comparative event estimates drawn from routine care data (Diabetes Obesity and Metabolism, 2026). A separate analysis published in JAMA examined patients with heart failure with preserved ejection fraction who were treated with semaglutide or tirzepatide and reported on heart failure related outcomes in that population (JAMA, 2025). Neither of those analyses was a randomized cardiovascular outcome trial pitting one medicine against the other, and both were framed by their authors as comparative observational evidence (Diabetes Obesity and Metabolism, 2026) (JAMA, 2025).

Class, Mechanism and How the Two Molecules Differ

Semaglutide is a glucagon-like peptide 1 receptor agonist, while tirzepatide acts at both the glucose-dependent insulinotropic polypeptide receptor and the GLP-1 receptor, a difference in receptor pharmacology described in a review of novel GLP-1 based medications for type 2 diabetes and obesity (Endocrine Reviews, 2026). That review summarised how incretin receptor signalling influences insulin secretion, gastric emptying and appetite regulation across the agents in this class (Endocrine Reviews, 2026).

Mechanistic work has examined the physiological pathways involved. A clinical study in people with type 2 diabetes reported that tirzepatide reduced appetite, lowered energy intake and decreased fat mass over the study period (Diabetes Care, 2023). Reviews of this class place such appetite and energy intake findings alongside effects on glycemic control when describing how the medicines were studied (Endocrine Reviews, 2026).

Interest in this class has also extended to specific clinical populations. A review of psychotropic drug related weight gain discussed pharmacological approaches that have been studied for weight gain associated with psychiatric medicines, including incretin based agents (American Journal of Psychiatry, 2024).

Regulatory Status

Both molecules are approved prescription medicines in the United States. Semaglutide is approved in subcutaneous and oral formulations for use in type 2 diabetes and, as a separate subcutaneous product, for chronic weight management in adults meeting defined criteria. Tirzepatide is approved as a subcutaneous prescription medicine for type 2 diabetes and, as a separate product, for chronic weight management in adults meeting defined criteria. Approved labelling, indications and population criteria are set by regulators and are updated over time, so the current prescribing information and a licensed clinician are the appropriate sources for status in any individual case. Published trials of each medicine, including the two head-to-head trials, were conducted in defined populations with protocol-specified monitoring (NEJM, 2021) (NEJM, 2025).

Adverse Events in the Comparative Literature: What Studies Report

In SURPASS-2, researchers reported that the most common adverse events in both the tirzepatide groups and the semaglutide group were gastrointestinal, including nausea, diarrhea and vomiting, and that these events were primarily mild to moderate in severity, with hypoglycemia reported infrequently across the groups studied (NEJM, 2021). In SURMOUNT-5, the study reported that gastrointestinal adverse events were the most frequent events in both groups and were mostly mild to moderate (NEJM, 2025).

The matched observational cohort comparing the two medicines in adults with overweight or obesity reported rates of gastrointestinal adverse events in both treatment groups alongside its weight outcomes (JAMA Internal Medicine, 2024). Pooled analyses have also reported tolerability signals: a meta-analysis of randomized trials lasting at least 20 weeks reported adverse event and discontinuation data for tirzepatide against its comparators (Journal of Obesity, 2025), and a broad meta-analysis of obesity pharmacotherapy reported safety outcomes including treatment discontinuation due to adverse events across agents (Nature Medicine, 2025). A network meta-analysis in type 2 diabetes reported comparative tolerability alongside efficacy estimates for the two medicines (Diabetologia, 2024).

What the Comparative Literature Leaves Open

• Open-label design. Both head-to-head trials were open-label, a design feature described in each report (NEJM, 2021) (NEJM, 2025).
• Comparator dose selection. The semaglutide dose studied in the diabetes trial differed from the higher dose studied in the obesity trial, as recorded in the design table above (NEJM, 2021) (NEJM, 2025).
• Outcome scope. The randomized head-to-head endpoints were glycemic and anthropometric rather than long term cardiovascular event rates, and comparative cardiovascular data to date have come from observational analyses (Diabetes Obesity and Metabolism, 2026) (JAMA, 2025).
• Population limits. Trial populations were defined by entry criteria, so findings describe the groups enrolled rather than every clinical situation (NEJM, 2025).

Related Reading

• Semaglutide: what the research describes
• Tirzepatide: what the research describes

References

• Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes (The New England Journal of Medicine, 2021)
• Tirzepatide as Compared with Semaglutide for the Treatment of Obesity (The New England Journal of Medicine, 2025)
• Semaglutide vs Tirzepatide for Weight Loss in Adults With Overweight or Obesity (JAMA Internal Medicine, 2024)
• Subcutaneously administered tirzepatide vs semaglutide for adults with type 2 diabetes: a systematic review and network meta-analysis of randomised controlled trials (Diabetologia, 2024)
• GLP-1 Receptor/Dual Agonists for Weight Loss: A Systematic Review and Network Meta-Analysis of RCTs (Diabetes, Obesity and Metabolism, 2026)
• Weight Loss Efficacy of Tirzepatide Compared to Placebo or GLP-1 Receptor Agonists in Adults With Obesity or Overweight: A Meta-Analysis of Randomized Controlled Trials With at Least 20 Weeks Treatment Duration (Journal of Obesity, 2025)
• A systematic review and meta-analysis of the efficacy and safety of pharmacological treatments for obesity in adults (Nature Medicine, 2025)
• Novel GLP-1-based Medications for Type 2 Diabetes and Obesity (Endocrine Reviews, 2026)
• Tirzepatide Reduces Appetite, Energy Intake, and Fat Mass in People With Type 2 Diabetes (Diabetes Care, 2023)
• Semaglutide and tirzepatide effects on cardiovascular outcomes in people with overweight or obesity in the real world (STEER) (Diabetes, Obesity and Metabolism, 2026)
• Semaglutide and Tirzepatide in Patients With Heart Failure With Preserved Ejection Fraction (JAMA, 2025)
• Psychotropic Drug-Related Weight Gain and Its Treatment (The American Journal of Psychiatry, 2024)