Semaglutide vs Tirzepatide
For laboratory and research use only. Not for human or veterinary use. This page summarizes published scientific literature for educational purposes only.
Semaglutide and tirzepatide are the two most-compared compounds in incretin research. The core difference is simple: semaglutide engages one receptor, tirzepatide engages two. This guide breaks down what that means mechanistically and what the published literature reports. It is part of our GLP-1 research peptides hub.
The core difference
Semaglutide is a single GLP-1 receptor agonist. Tirzepatide is a dual agonist that engages both the GIP receptor and the GLP-1 receptor. The added GIP arm is the defining distinction between the two molecules, and it is the reason tirzepatide is often described in the literature as a next-generation incretin compound.
Mechanism comparison
- Semaglutide — GLP-1 only. Glucose-dependent insulin secretion, slowed gastric emptying, and appetite signaling through a single receptor pathway.
- Tirzepatide — GIP + GLP-1. The GLP-1 actions above, plus activation of the GIP receptor, a second incretin pathway that contributes additional insulinotropic and satiety signaling.
For context, the next step beyond dual agonism is the triple agonist retatrutide, which adds a third (glucagon) receptor arm.
What the clinical literature reports
Both molecules have been characterized in large sponsor-run clinical programs on their respective drug products: the STEP and SUSTAIN programs for semaglutide, and the SURMOUNT and SURPASS programs for tirzepatide, with results published in journals including the New England Journal of Medicine. These trials studied approved drug products in humans, not research-grade material, and are referenced here only to explain the science. Primary sources are available on PubMed.
Quick comparison
- Receptors: semaglutide = GLP-1; tirzepatide = GIP + GLP-1
- Class: semaglutide = single agonist; tirzepatide = dual agonist
- Research clinical programs: STEP / SUSTAIN vs SURMOUNT / SURPASS
- Form supplied: both as lyophilized, HPLC-characterized research powder
Dosing used in the clinical trials
The following reports the dose regimens administered in published clinical trials of the semaglutide and tirzepatide drug products, for scientific context only. It is not a recommendation, a protocol, or guidance for use, and it does not describe how the research-grade material sold here should be used. Self-administering research peptides can be dangerous; these products are strictly for laboratory research.
Both molecules were studied with once-weekly subcutaneous dosing and a gradual 4-week escalation, but the ladders and maintenance ceilings differ.
Semaglutide weekly dose — STEP 1 (NEJM 2021)
Tirzepatide weekly dose — SURMOUNT 1 (NEJM 2022)
Note: milligram doses are not directly comparable between the two molecules — they differ in potency. Approved maintenance doses are 2.4 mg (semaglutide) and 5/10/15 mg (tirzepatide).
At maintenance, STEP 1 reported about 14.9% mean weight loss (2.4 mg) and SURMOUNT 1 reported about 15% (5 mg), 19.5% (10 mg), and up to roughly 20.9–22.5% (15 mg). Sources: STEP 1 (NEJM 2021); SURMOUNT 1 (NEJM 2022).
Side-by-side: doses studied and outcomes reported
The values below come directly from the published trials of the approved drug products, for scientific context only — not a recommendation and not a dose conversion. Milligrams are not interchangeable between the two molecules.
| Compound | Trial | Weekly maintenance dose | Mean weight change |
|---|---|---|---|
| Semaglutide | STEP 1 (obesity, 68 wk) | 2.4 mg | about -14.9% |
| Tirzepatide | SURMOUNT 1 (obesity, 72 wk) | 5 mg | about -15% |
| Tirzepatide | SURMOUNT 1 | 10 mg | about -19.5% |
| Tirzepatide | SURMOUNT 1 | 15 mg | about -20.9% |
Sources: STEP 1 (Wilding et al., NEJM 2021); SURMOUNT 1 (Jastreboff et al., NEJM 2022). Obesity trials in participants without type 2 diabetes.
Head-to-head: the SURPASS-2 trial
The clearest direct comparison in the literature is SURPASS-2 (Frias et al., NEJM 2021), which studied both molecules in the same randomized trial — tirzepatide at 5, 10, and 15 mg against semaglutide at 1 mg, in adults with type 2 diabetes on metformin over 40 weeks. Because the doses were fixed by the trial design, this is comparative outcome data, not a conversion between doses.
| Trial arm | Mean A1c reduction | Mean weight change |
|---|---|---|
| Semaglutide 1 mg | about -1.9% | about -5.7 kg |
| Tirzepatide 5 mg | about -2.0% | about -7.6 kg |
| Tirzepatide 10 mg | about -2.2% | about -9.3 kg |
| Tirzepatide 15 mg | about -2.3% | about -11.2 kg |
Source: SURPASS-2 (Frias et al., NEJM 2021), type 2 diabetes, 40 weeks. Values approximate; see the primary publication for exact figures.
Is there a semaglutide-to-tirzepatide dose conversion?
From the published literature, no. There is no validated dose-equivalence that converts a semaglutide dose into a tirzepatide dose — the two differ in potency and mechanism, and no trial was designed to produce a conversion factor. Their milligram scales are not interchangeable: the approved semaglutide maintenance dose is 2.4 mg, while tirzepatide maintenance is 5, 10, or 15 mg. What the research provides is the per-drug outcome data and the SURPASS-2 head-to-head shown above. Any “1 mg equals X mg” figure circulating online is an informal community estimate, not a result from the trial data.
Laboratory handling
Both compounds ship lyophilized and are reconstituted with sterile bacteriostatic water before use. The reconstitution calculator returns the exact diluent volume for either one, and Certificates of Analysis are on the Lab Results page. Browse both in the GLP-1 catalog; bacteriostatic water is included free with every order.
Frequently asked questions
What is the main difference between semaglutide and tirzepatide?
Semaglutide activates the GLP-1 receptor only; tirzepatide activates both the GIP and GLP-1 receptors. Tirzepatide is therefore a dual agonist and semaglutide a single agonist.
Which is “stronger”?
That framing applies to clinical drug products, not research material. Mechanistically, tirzepatide engages an additional receptor arm; the relevant clinical comparisons are documented in the published SURMOUNT and STEP literature.
Are they handled differently in the lab?
No — both are lyophilized peptides reconstituted with bacteriostatic water and characterized by HPLC with a COA.
Disclaimer: Research-grade semaglutide and tirzepatide supplied by MyGLP1Store are strictly for laboratory and in-vitro research. They are not approved drugs, not supplements, and not for human or veterinary use. Clinical trial data above pertains to pharmaceutical drug products studied by their sponsors.