Retatrutide 20mg

RetaLABS Retatrutide 20mg is a lyophilised research vial of LY3437943, a triple GLP-1, GIP, and Glucagon receptor agonist developed by Eli Lilly. At the 4mg/week starting dose used in Phase 2 cohorts, a single 20mg vial supplies five weeks of research. At the 8mg/week maintenance dose, it covers approximately 2.5 weeks of protocol. The 20mg format is the most common choice for Australian researchers running short-to-medium-duration Phase 2-style cohorts; researchers planning long maintenance protocols typically prefer the 30mg vial for fewer reconstitution events.

Supplied as a white lyophilised powder. Shipped via Express Post Australia-wide in discrete, unmarked packaging, typically dispatched within 1–2 business days of confirmed crypto payment (BTC, LTC, or XMR).

Why Retatrutide Is Mechanistically Distinct

Retatrutide is the first triple receptor agonist in human clinical trials in the GLP-1 class. The compound simultaneously activates three receptors that have historically been engaged separately or in pairs:

• GLP-1R (Glucagon-Like Peptide-1 Receptor). Drives glucose-dependent insulin secretion, suppresses glucagon, slows gastric emptying, and signals satiety via hypothalamic and brainstem pathways. This is the receptor engaged by Semaglutide and the GLP-1 component of Tirzepatide.
• GIPR (Glucose-dependent Insulinotropic Polypeptide Receptor). Amplifies beta-cell insulin secretion through pathways distinct from GLP-1R, modulates adipose tissue lipid handling, and appears to reduce the GI adverse-event burden associated with isolated GLP-1R agonism. This is the second receptor engaged by Tirzepatide (the "twincretin" target).
• GcgR (Glucagon Receptor). The third receptor, unique to Retatrutide among the three primary research-grade GLP-1 class peptides. GcgR agonism drives hepatic fatty acid oxidation and thermogenesis, adding an energy-expenditure mechanism on top of the appetite-suppression and insulin-secretion mechanisms of GLP-1R/GIPR.

For the full mechanism explainer including how GcgR's glucose-raising effect is offset by GLP-1R co-agonism, see the Glucagon Receptor Explained entity page. For the GLP-1 entity overview see GLP-1 Explained.

Phase 2 Trial Data, What Researchers Are Working From

The pivotal Phase 2 trial (Jastreboff et al., NEJM 2023, NCT04881760) enrolled 338 adults across six cohorts over 48 weeks. Top-line outcomes at the 48-week primary endpoint, by dose:

Dose cohort	Mean weight loss	Placebo-adjusted
Placebo	2.1%	-
1mg/week	8.7%	~6.6%
4mg/week (fast titration)	17.3%	~15.2%
8mg/week	22.8%	~20.7%
12mg/week	24.2%	~22.1%

Secondary endpoint magnitudes at the 12mg cohort: approximately 41% mean reduction in fasting insulin; approximately 43% mean reduction in triglycerides; approximately 18.5 cm mean reduction in waist circumference; meaningful reduction in liver fat fraction on MRI in the measured subset. Cardiometabolic biomarkers including HbA1c, LDL cholesterol, and blood pressure also improved across active cohorts.

The 20mg vial covers the early cohort durations of every Phase 2 escalation schedule. At the 4mg/week dose level (Phase 2 starting maintenance dose for the lower cohorts), a single 20mg vial supplies five weekly doses. The 8mg/week cohort uses one 20mg vial across approximately 2.5 weeks; the 12mg/week cohort consumes a 20mg vial in approximately 1.7 weeks at full maintenance dose. Researchers running longer maintenance phases at peak doses generally combine 20mg and 30mg vial purchases or rely on the 30mg format alone.

For the full Phase 2 statistics including adverse event rates, discontinuation breakdown, and cohort-by-cohort numbers, see the Retatrutide Statistics 2026 data page.

Cross-Compound Comparison

Retatrutide research is most usefully contextualised against the two other compounds in the GLP-1 receptor agonist class with the strongest published trial data. The following table is cross-trial (drawn from separate studies with different populations, durations, and dose designs, not a head-to-head trial) so direct ranking requires caution:

Metric	Semaglutide	Tirzepatide	Retatrutide
Receptor targets	GLP-1R	GLP-1R + GIPR	GLP-1R + GIPR + GcgR
Compound class	Single	Dual (twincretin)	Triple agonist
Developer	Novo Nordisk	Eli Lilly	Eli Lilly
Pivotal trial	STEP 1, 68 weeks	SURMOUNT-1, 72 weeks	Phase 2, 48 weeks
Trial enrolment	1,961	2,539	338
Highest dose	2.4mg/week	15mg/week	12mg/week
Mean weight loss (highest dose)	14.9%	20.9%	24.2%
Half-life	~7 days	~5 days	~6 days
Phase 3 status	Complete	Complete	TRIUMPH ongoing

For full side-by-side comparisons see Retatrutide vs Tirzepatide and Retatrutide vs Semaglutide.

Reconstitution at a Glance

The most common research-protocol approach for a 20mg vial: add 2.0mL bacteriostatic water to produce a 10mg/mL working concentration. At this concentration, individual dose volumes on a standard U100 insulin syringe are:

Dose	Volume at 10mg/mL	U100 syringe units
2 mg	0.20 mL	20 units
4 mg	0.40 mL	40 units
6 mg	0.60 mL	60 units
8 mg	0.80 mL	80 units

Reconstitution technique: inject the bacteriostatic water slowly down the inner wall of the vial, swirl gently (do not shake), and store the reconstituted solution refrigerated at 2–8°C. The bacteriostatic water diluent contains 0.9% benzyl alcohol as a preservative, supporting multiple withdrawals from the same vial across an approximately 4-week stability window. For full protocol detail see the Peptide Reconstitution & Storage Guide and the reconstitution calculator.

Sourcing, Quality & Documentation

RetaLABS Retatrutide is supplied as research-grade, manufacturer-verified lyophilised peptide. Each batch is purity-tested by HPLC. Where a batch is published, its Certificate of Analysis appears on this page; full batch documentation is available on request, email support@retalabs.is with your order number.

All Retatrutide vials are supplied for laboratory research use only. Retatrutide is not approved as a therapeutic in Australia (TGA register confirmed); it has not completed Phase 3 trials in any jurisdiction. By placing an order you confirm the compound is acquired for research purposes and not for human consumption. For the regulatory framework see Retatrutide Legal Status in Australia.

Primary Research References

The core peer-reviewed publications underlying current Retatrutide research:

• Jastreboff AM et al. "Triple-Hormone-Receptor Agonist Retatrutide for Obesity, A Phase 2 Trial." New England Journal of Medicine, 2023; 389:514-526. doi:10.1056/NEJMoa2301972. The pivotal Phase 2 dose-finding study. NCT04881760.
• Coskun T et al. "LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: From discovery to clinical proof of concept." Cell Metabolism, 2022; 34:1234-1247. doi:10.1016/j.cmet.2022.07.013. Original receptor-binding characterisation and Phase 1 pharmacokinetic profile.
• Rosenstock J et al. "Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial conducted in the USA." The Lancet, 2023; 402:529-544. doi:10.1016/S0140-6736(23)01053-X. Phase 2 trial in adults with type 2 diabetes.
• Sanyal AJ et al. "Triple Hormone Receptor Agonist Retatrutide for Metabolic Dysfunction-Associated Steatotic Liver Disease: a randomised, double-blind, placebo-controlled, phase 2a trial." Nature Medicine, 2024; 30:2037-2048. Phase 2a MASH/NAFLD trial; positions Retatrutide for the TRIUMPH-NAFLD Phase 3.
• ClinicalTrials.gov registrations: Phase 2 trial NCT04881760; Phase 3 TRIUMPH-1 NCT05882045, TRIUMPH-2 NCT05882049, TRIUMPH-3 NCT05882077, TRIUMPH-4 NCT05989711, SYNERGY-OUTCOMES NCT06077864, TRIUMPH-NAFLD NCT06324877.

The RetaLABS Research Team's editorial and sourcing methodology is documented at the RetaLABS Research Team profile.

Related Research Reading

The full Retatrutide research cluster:

• Retatrutide Research Guide, full mechanism, trial data, reconstitution, sourcing
• Retatrutide Statistics 2026, quick-facts data block, cohort numbers, trial registry
• Phase 3 TRIUMPH Update, current trial status across the TRIUMPH programme
• Dosing Protocol Reference, Phase 2 escalation schedule + reconstitution maths
• Side Effects (Phase 2 Data), full AE profile and discontinuation breakdown
• Retatrutide vs Tirzepatide, triple vs dual agonist research comparison
• Retatrutide vs Semaglutide, triple agonist vs GLP-1 single-receptor comparison