Retatrutide and tirzepatide are next-generation incretin peptides that both act on the GIP and GLP-1 receptors, but retatrutide adds a third target: the glucagon receptor. Tirzepatide is an approved medicine (marketed as Mounjaro and Zepbound), while retatrutide remains investigational and has only completed Phase 2 studies. That difference in development stage shapes almost everything else, from the strength of the evidence to how each compound is available. This comparison lays out the mechanisms, the published trial data and the practical distinctions side by side.
| Attribute | Retatrutide | Tirzepatide |
|---|---|---|
| Receptor targets | Triple agonist: GIP + GLP-1 + glucagon | Dual agonist: GIP + GLP-1 |
| Drug class | Investigational triple incretin agonist | Incretin (twincretin) GIP/GLP-1 agonist |
| Regulatory status | Investigational — Phase 2 only, not approved | Approved (EMA/FDA) for type 2 diabetes and weight management |
| Brand names | None (no approved product) | Mounjaro, Zepbound |
| Trial weight-loss data | ~24% mean at 48 weeks, highest dose (Phase 2, NEJM 2023) | ~20–22% at the highest dose over 72 weeks (SURMOUNT-1) |
| Dosing frequency | Once weekly (subcutaneous) in trials | Once weekly (subcutaneous) |
| Primary study focus | Obesity and metabolic disease (early stage) | Glycaemic control (SURPASS) and obesity (SURMOUNT) |
| Body Pharm EU availability | Pre-loaded pen (not an approved medicine) | Pre-loaded pen (not Mounjaro or Zepbound) |
Tirzepatide is a single molecule engineered to activate two incretin receptors at once — GIP and GLP-1 — which together improve insulin secretion, slow gastric emptying and reduce appetite signalling. Retatrutide keeps both of those targets and adds glucagon-receptor agonism. Glucagon activation is thought to raise energy expenditure and influence hepatic fat metabolism, which is the mechanistic rationale for the larger weight changes seen in its early trials. The trade-off is that adding a third pathway makes the pharmacology more complex and is precisely why retatrutide still needs large confirmatory studies.
Tirzepatide has an extensive, mature evidence base. The SURPASS programme established its glycaemic effect in type 2 diabetes, and SURMOUNT-1 reported roughly 20–22% mean body-weight reduction at the highest dose over 72 weeks in people with obesity. Retatrutide, by contrast, is supported by a single widely cited Phase 2 obesity trial (published in the New England Journal of Medicine in 2023) in which the highest-dose group lost about 24% of body weight at 48 weeks. Those headline numbers are not directly comparable — different trial lengths, populations and designs — and a Phase 2 result is far less certain than tirzepatide's completed Phase 3 programme.
The single most important distinction is regulatory status: tirzepatide is an approved medicine available on prescription through pharmacies, whereas retatrutide is not approved anywhere and remains an investigational compound. Beyond that, the mechanisms differ (dual vs triple agonism), the depth of safety data differs (years of post-approval use vs early-phase exposure), and the confidence you can place in the efficacy figures differs accordingly. Both are dosed once weekly by subcutaneous injection in their respective studies.
We supply both retatrutide and tirzepatide as pre-loaded pens: RETATRUTIDE 32, RETATRUTIDE 64 and TIRZEPATIDE 60. None of them is an approved medicine. They are not Mounjaro, Zepbound or any other licensed product, and if you are looking for an approved treatment, that decision belongs with a clinician who can prescribe one.
Tirzepatide is the established, approved option with the deeper evidence base. Retatrutide is the more experimental triple agonist, whose early data look striking but remain unconfirmed by Phase 3 trials. Neither is "better" in the abstract: tirzepatide offers regulated, trial-proven efficacy today, and retatrutide is the leading edge of the class, still to prove itself.
Early Phase 2 data for retatrutide showed a larger mean weight change (~24% at 48 weeks) than tirzepatide reported in SURMOUNT-1 (~20–22% at 72 weeks), but the trials differ in length, design and population, so they cannot be compared head-to-head. Retatrutide's figures also come from a much earlier stage of development and are not yet confirmed.
Tirzepatide activates two incretin receptors (GIP and GLP-1). Retatrutide activates those two plus the glucagon receptor, making it a triple agonist. The added glucagon activity is the main mechanistic reason it is being studied for larger metabolic effects.
No. Tirzepatide is approved by the EMA and FDA and marketed as Mounjaro and Zepbound. Retatrutide is investigational, has only completed Phase 2 trials, and is not approved anywhere.
Yes. We stock both as pre-loaded pens, at two strengths for retatrutide. They are not approved medicines, and the certificate of analysis for each batch is published on our certificates page.
Both compounds are administered once weekly by subcutaneous injection in their respective clinical trials.
This page is educational and intended for research and informational use only. It is not medical advice, a treatment recommendation, or dosing guidance, and it makes no promises about outcomes. Retatrutide, tirzepatide and semaglutide are the active pharmaceutical ingredients studied in clinical trials; approved medicines are supplied only through licensed pharmacies with a prescription. Body Pharm EU supplies research-grade materials for laboratory use, not approved medicines, and nothing here should be read as a substitute for advice from a qualified healthcare professional.
These two get compared on headline weight-loss percentages more than any other pairing in the category. The percentages are real. They were generated at completely different stages of clinical development, and that difference matters more than the gap between the numbers.
Jastreboff AM et al. Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. N Engl J Med 2023. PMID 37366315; Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med 2022. PMID 35658024; SURMOUNT-1, NCT04184622
No study has administered retatrutide and tirzepatide to comparable groups at the same time and measured the difference. Every comparison you will read, including this one, lines up results from separate trials with separate protocols, populations, durations and endpoints.
That is a legitimate thing to do carefully and a misleading thing to do casually.
Retatrutide (what retatrutide is): Phase 2, 48 weeks, around 24% mean weight reduction at the highest dose. A Phase 2 trial establishes a signal and informs dose selection.
Tirzepatide: Phase 3, 72 weeks, mean change of −15.0%, −19.5% and −20.9% at 5, 10 and 15 mg against −3.1% for placebo. Phase 3 is the evidence base on which a medicine is authorised, and tirzepatide is authorised.
Different durations, different phases, different regulatory outcomes. Putting 24% next to 20.9% and concluding retatrutide is stronger ignores every one of those differences.
Tirzepatide is a dual agonist: GIP and GLP-1 (tirzepatide, explained). Retatrutide adds a third receptor, glucagon. Glucagon receptor activity is the genuinely novel element and what separates retatrutide from everything else in the class.
Whether three receptors beats two is exactly what a Phase 3 programme would establish. It has not run.
Tirzepatide holds an EU marketing authorisation. Retatrutide holds none anywhere, has no completed Phase 3 programme, and remains investigational: in active clinical development, a real and specific status distinct from both “approved” and “abandoned”.
For you that is more consequential than any percentage: one has an approved dose, prescribing information, pharmacy supply and post-marketing surveillance behind it. The other does not, and neither does a pre-loaded pen of either compound. Ours are RETATRUTIDE 32, RETATRUTIDE 64 and TIRZEPATIDE 60.
Gastrointestinal adverse events are the characteristic, dose-related pattern for the class. Both programmes used slow upward titration over months rather than starting at a target dose. We publish no dosing schedule; the protocols are public in the papers above.
Related: incretin peptides, Tirzepatide vs Semaglutide, everything we list for weight loss.
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