Retatrutide vs Tirzepatide vs Semaglutide
The three differ by how many receptors they act on: semaglutide acts on GLP-1 alone, tirzepatide on GIP and GLP-1, and retatrutide on GIP, GLP-1 and glucagon. Tirzepatide has the largest trial record and is registered on the ARTG as Mounjaro; retatrutide is still investigational. Semaglutide is not sold here and has no page on this site.
Side by side
| Retatrutide | Tirzepatide | Semaglutide | |
|---|---|---|---|
| Class | Triple receptor agonist (GIP, GLP-1, glucagon); developed as LY3437943 | Dual receptor agonist (GIP, GLP-1) | Selective GLP-1 receptor agonist |
| What's studied | Body weight, HbA1c, liver fat, body composition and appetite in obesity and type 2 diabetes | Type 2 diabetes (SURPASS), obesity (SURMOUNT), sleep apnoea, heart failure with preserved ejection fraction, MASH | On this site, only as a comparator: against tirzepatide in SURPASS-2, and alone or with cagrilintide (CagriSema) in the cagrilintide trials |
| Strength of the evidence | Human phase 1b and phase 2 trials, and one phase 3 trial in type 2 diabetes (n=537); 12 to 48 weeks | Large human phase 3 programmes (SURMOUNT-1 n=2539; SURPASS-2 n=1879), with a 3-year SURMOUNT-1 analysis | Human phase 3 trials, cited here only where semaglutide was a comparator arm |
| Forms sold here | Lyophilised powder vial; pre-filled pen | Lyophilised powder vial | Not sold here |
| Sizes sold here | 10, 20 and 30 mg vials; 15, 20, 30 and 70 mg pens | 20 and 40 mg vials | Not sold here |
| Storage | Vial: −20 °C, dry and dark; 2–8 °C once mixed. Pen: 2–8 °C, protected from light, not frozen | −20 °C, dry and dark; 2–8 °C once mixed, use within 28 days | Not covered on this site |
| Status in Australia | Not registered on the ARTG; investigational | Registered on the ARTG as Mounjaro (prescription medicine); the research powder is not Mounjaro | Not covered on this site |
| Cited studies on our pages | 6 | 8 | No page; a semaglutide-alone arm appears in 1 tirzepatide study and 3 cagrilintide studies |
Key differences
Receptors: semaglutide acts on the GLP-1 receptor only, tirzepatide adds the GIP receptor, and retatrutide adds the glucagon receptor on top of both. Glucagon acts on the liver and energy use, which is why the retatrutide trials also measured liver fat.
Head-to-head data: the only direct comparison among the studies we cite is SURPASS-2, where tirzepatide lowered HbA1c by 2.01 to 2.30 percentage points against 1.86 with semaglutide over 40 weeks in type 2 diabetes. None of our cited studies compares retatrutide directly with tirzepatide or semaglutide; its trials used placebo or dulaglutide.
Stage of development: tirzepatide is an approved medicine in Australia as Mounjaro, backed by phase 3 programmes. Retatrutide is investigational, with phase 2 results published in 2023 and one phase 3 type 2 diabetes trial published in 2026. The material sold here for both is research-grade, not the pharmaceutical product.
FAQ
What is the difference between retatrutide, tirzepatide and semaglutide?
They act on different numbers of hormone receptors. Semaglutide is a GLP-1 receptor agonist, tirzepatide activates GIP and GLP-1 receptors, and retatrutide activates GIP, GLP-1 and glucagon receptors. All three were given as once-weekly injections in their published trials.
Does Tasman sell semaglutide?
No. Semaglutide is not sold here and has no page on this site. It appears in this comparison because it is the usual reference point, and the facts in its column come only from studies on our tirzepatide and cagrilintide pages, where it was a comparator.
Has retatrutide been compared directly with tirzepatide?
Not in the studies we cite. The retatrutide trials on our page compared it with placebo or with dulaglutide. The only head-to-head trial in this set is SURPASS-2, tirzepatide against semaglutide in type 2 diabetes.
Are these compounds legal in Australia?
Tirzepatide is registered on the ARTG as the prescription medicine Mounjaro; that registration covers the finished product, not research-grade powder. Retatrutide is not registered on the ARTG. Tasman supplies retatrutide and tirzepatide as research chemicals for laboratory research only, not for human consumption.