Retatrutide vs Tirzepatide (and Semaglutide): Full Comparison

Retatrutide vs tirzepatide vs semaglutide at a glance

The weight figures come from different trials with different populations and durations, so they are not a direct comparison. Tirzepatide and retatrutide share a length and a similar design lineage: both are Lilly peptides with a C20 fatty diacid for albumin binding.

Receptors: what the glucagon component adds

Semaglutide works through GLP-1 alone: insulin release, slower gastric emptying and appetite reduction. Tirzepatide adds GIP, and it is actually more potent at the GIP receptor than at GLP-1. Retatrutide keeps that GIP-heavy balance (structural work in Cell Discovery in 2024 put it at about 8.9 times native GIP potency) and adds partial glucagon receptor activity, at about 0.3 times native glucagon.

Glucagon receptor activity raises energy expenditure and drives fat breakdown in the liver. That is the plausible reason retatrutide's liver fat results were so large (86.0% relative reduction at 48 weeks on 12 mg in the Nature Medicine 2024 substudy), and why researchers treat it as a separate question rather than a stronger tirzepatide. For more on the molecule itself, see what retatrutide is.

Tirzepatide vs retatrutide: trial results side by side

Each compound's flagship obesity trial, in adults without diabetes:

• Tirzepatide, SURMOUNT-1 (Jastreboff et al., NEJM, 2022): 72 weeks, mean weight change of 15.0% (5 mg), 19.5% (10 mg) and 20.9% (15 mg), against 3.1% on placebo.
• Retatrutide, phase 2 (Jastreboff et al., NEJM, 2023): 48 weeks, 17.1% (4 mg), 22.8% (8 mg) and 24.2% (12 mg), against 2.1% on placebo.
• Retatrutide, TRIUMPH-1 (Lilly topline, May 2026): mean loss at 80 weeks was 28.3% on 12 mg, 25.9% on 9 mg and 19.0% on 4 mg.
• Semaglutide 2.4 mg, STEP 1 (Wilding et al., NEJM, 2021): 68 weeks, 14.9% against 2.4% on placebo.

Tirzepatide and semaglutide have also been compared directly: in SURMOUNT-5 (NEJM, 2025), tirzepatide produced 20.2% weight loss against 13.7% for semaglutide at 72 weeks. The equivalent retatrutide trial is TRIUMPH-5, about 800 adults randomised to retatrutide or tirzepatide with an 80-week weight endpoint. ClinicalTrials.gov lists its estimated completion as December 2026. Until it reports, anyone claiming to know what's better, tirzepatide or retatrutide, is comparing across trials. Our retatrutide results guide has the full timepoint data.

Side effects compared

All three share the incretin side effect profile: nausea, diarrhoea, vomiting and constipation, dose related and concentrated in escalation. The numbers at the top doses:

Retatrutide also has a signal the others do not: dysesthesia, an altered skin sensation, reported in 20.9% of the 12 mg group in TRIUMPH-4 against 0.7% on placebo. And tirzepatide and semaglutide have years of post-marketing safety data, which retatrutide cannot have until it is approved. Details are in our retatrutide side effects guide.

Retatrutide vs Mounjaro and retatrutide vs Ozempic

Mounjaro is the brand name for tirzepatide, registered by the TGA for type 2 diabetes and, since September 2024, for chronic weight management in adults. Ozempic is semaglutide registered for type 2 diabetes in Australia; Wegovy is the semaglutide product registered for weight management. All three are prescription medicines. So retatrutide vs Mounjaro is really retatrutide vs tirzepatide, and retatrutide vs Ozempic is retatrutide vs semaglutide at diabetes doses (STEP 1 used the 2.4 mg Wegovy dose).

The practical difference in Australia is regulatory, not pharmacological. Mounjaro and Ozempic have been evaluated by the TGA for quality, safety and efficacy. Retatrutide has not, and the TGA has warned against using it outside a clinical trial. Research-grade tirzepatide from a peptide supplier is also not Mounjaro: it is not a registered medicine, has not been assessed by the TGA, and is sold for laboratory work only. More on the Australian position is in is retatrutide available in Australia.

Choosing between them for laboratory research

Our view: for a lab, the question is rarely which compound is better; it is which receptor contribution you need to isolate. Tirzepatide is the better-characterised reference compound, with a large published literature, so it makes the natural dual-agonist comparator. Retatrutide is the variable when the study asks what glucagon receptor activity adds, for example in energy expenditure or liver lipid work. Many designs run both, and add cagrilintide, a long-acting amylin analogue, to probe a separate satiety pathway.

Formats matter too. Research tirzepatide comes as the Tirzepatide Pen in a 3 mL cartridge, and retatrutide as 10, 20 and 30 mg vials or the 10 mg Retatrutide Pen. Both compounds go through the same independent checks on every lot, mass spectrometry for identity and HPLC for purity, and the lot number printed on each vial links to a certificate on the COA lookup. The retatrutide calculator handles reconstitution volumes, and both sit in our metabolic research peptides range.

Order Retatrutide and Tirzepatide Online for Comparator Studies

For a head-to-head design, buy both compounds from one supplier so the two certificates report identity and purity the same way. A sensible starting order is the 10 mg retatrutide vial ($129) with the 2 mg tirzepatide vial ($59); labs that want the comparator already in solution can buy the Tirzepatide Pen at $149 instead. Adding an amylin arm? The 5 mg cagrilintide vial costs $69. Shop the set online from Australian stock, then buy bacteriostatic water sized to the number of vials you plan to reconstitute.

Research use only: AminoBlend supplies these compounds for laboratory research, not for human or veterinary use. Nothing on this page is medical advice or a recommendation to use any product.