PeptidesInfo

Comparison

Semaglutide vs tirzepatide

The two approved incretin peptides for weight and glucose compared on trial results, mechanism, approvals, cardiovascular evidence, and what remains uncertain.

Updated

Bottom line

Both are FDA-approved with large randomised trials showing substantial weight loss and glycaemic improvement. Tirzepatide produced greater weight loss in its own trials and in the SURMOUNT-5 head-to-head trial; semaglutide has a longer track record and dedicated cardiovascular-outcome evidence (SELECT). Neither is 'safer' in a way the data can support; side-effect profiles are similar and GI-dominated.

Dimension
Semaglutide
Established evidenceFDA-approved for this use
Tirzepatide
Established evidenceFDA-approved for this use
MechanismGLP-1 receptor agonistDual GIP and GLP-1 receptor agonist
FDA approvalsType 2 diabetes (Ozempic, Rybelsus); chronic weight management (Wegovy); CV risk reduction (Wegovy, 2024)Type 2 diabetes (Mounjaro); chronic weight management (Zepbound); obstructive sleep apnoea with obesity (Zepbound, 2024)
Weight loss in pivotal trialsSTEP 1: mean −14.9% vs −2.4% placebo at 68 weeks (2.4 mg weekly)SURMOUNT-1: mean −15.0% to −20.9% vs −3.1% placebo at 72 weeks (5–15 mg weekly)
Head-to-headSURMOUNT-5 (2025): semaglutide 2.4 mg −13.7% at 72 weeksSURMOUNT-5 (2025): tirzepatide 15 mg −20.2% at 72 weeks
Cardiovascular outcomesSELECT: 20% relative reduction in MACE in adults with CVD and overweight/obesity (no diabetes)SURPASS-CVOT (2025): non-inferior to dulaglutide for MACE in T2D with CVD; dedicated obesity CVOT ongoing
Evidence level (weight management)EstablishedEstablished
Common adverse effectsNausea, diarrhoea, vomiting, constipation; boxed warning for thyroid C-cell tumours (rodent)Nausea, diarrhoea, vomiting, constipation; boxed warning for thyroid C-cell tumours (rodent)
Weight regain after stoppingSTEP 1 extension: about two-thirds of lost weight regained at 1 year off drugSURMOUNT-4: switching to placebo led to ~14% regain over 52 weeks

The comparison the evidence can support

Tirzepatide produces more weight loss than semaglutide at approved doses. That was suggested by cross-trial comparison and confirmed by SURMOUNT-5, an open-label randomised head-to-head trial in adults with obesity without diabetes, which found roughly 20% versus roughly 14% mean weight loss at 72 weeks. Glycaemic control in type 2 diabetes was also greater with tirzepatide in SURPASS-2 versus semaglutide 1 mg.

The comparison it can't (yet)

Semaglutide has a completed cardiovascular-outcome trial in people with obesity but not diabetes (SELECT), which is why it carries a cardiovascular indication. Tirzepatide's SURPASS-CVOT showed non-inferiority to dulaglutide in type 2 diabetes with established cardiovascular disease, and a dedicated obesity outcomes trial is ongoing. "Which is better for your heart" is therefore not yet answerable on like-for-like data.

What they share

Both cause gastrointestinal effects that lead a meaningful minority to discontinue, both carry a boxed warning based on rodent thyroid tumours, and both are followed by substantial weight regain when stopped. Both are frequently counterfeited and were widely compounded during shortages that have now been declared resolved. The differences between them are smaller than the difference between either and any unapproved "metabolic peptide".

Go deeper

Research analysis5 min read

GLP-1 Peptides: Established Uses Versus Emerging Research

Semaglutide and tirzepatide are the best-evidenced peptides in medicine — for specific uses. We separate the approved indications with large trials from the emerging research (kidney, liver, heart failure, sleep apnoea, Alzheimer's) and the open questions about regain, muscle loss and compounded products.