Loading
Loading
LY3437943 · Triple agonist: GLP-1 / GIP / Glucagon
The most advanced triple-receptor agonist in clinical development. Phase II trials showed up to 24.2% mean body weight reduction at 48 weeks — outpacing both semaglutide and tirzepatide in head-to-head context.
⚠️ Official Health Alert — Victorian Dept of Health, 19 June 2026
Six cases of acute liver toxicity have been reported in Victoria in people who used products labelled Retatrutide. Investigations suggest the toxicity is likely caused by a contaminant in affected products, not Retatrutide itself — however the source of contamination has not yet been identified and all labelled products are considered at risk.
The Chief Health Officer advises: do not use any product labelled Retatrutide, Reta, R-10 or R-20. Anyone who has purchased such a product should stop use immediately and dispose of it safely.
All Capital Peptides products are independently third-party tested for purity and sourced from verified suppliers. If you have sourced Retatrutide from any other supplier, please exercise particular caution — the affected cases are believed to involve products purchased through unverified online or social media channels.
Symptoms to watch for: tiredness, jaundice, abdominal pain, dark urine, itchy skin, yellow eyes or skin, unusual bruising. Seek medical attention immediately if any occur.
Victorian Poisons Information Centre: 13 11 26 (24/7) · Emergency: 000 · health.vic.gov.au
Retatrutide is a synthetic peptide that simultaneously activates three hormone receptors: GLP-1 (glucagon-like peptide-1), GIP (glucose-dependent insulinotropic polypeptide), and glucagon. It was developed by Eli Lilly and is currently in Phase III clinical trials under the code name LY3437943.
In plain terms: GLP-1 tells your brain you're full and slows gastric emptying. GIP improves how fat tissue and muscle respond to insulin. Glucagon tells your liver to burn more fuel and raises your metabolic rate. Retatrutide fires all three signals at once — producing appetite suppression, improved insulin sensitivity, and elevated caloric burn simultaneously.
In Eli Lilly's Phase II results published in the New England Journal of Medicine (2023), participants receiving 12 mg/week lost a mean of 24.2% of body weight over 48 weeks. For comparison, semaglutide 2.4 mg achieves ~15% and tirzepatide 15 mg achieves ~20% over comparable durations.
Not on the FDA 503B compounding list
Eli Lilly trials expected to complete 2025–2026
Sold strictly as a research chemical for non-human use
GLP-1 agonists/peptide hormones are prohibited in-competition
No approved indication exists yet in any jurisdiction
In Australia, retatrutide has no TGA approval and is not available through compounding pharmacies. It is sold by Capital Peptides strictly as a research chemical for non-human, in-vitro, and laboratory research use only.
Retatrutide research is most relevant to protocols examining:
Weight loss research
Triple agonism produces superior fat mass reduction vs. single/dual agonists
Metabolic syndrome
Simultaneous effects on glucose, lipids, and appetite pathway regulation
Hepatic fat clearance
Glucagon axis drives liver triglyceride mobilisation and fatty acid oxidation
Receptor pharmacology
Ideal for studying multi-receptor agonism vs. individual axis contributions
Adaptation phase
Appetite signals begin to shift. Mild nausea common while the gut adapts to GLP-1 agonism. Stick to the lowest dose.
Early fat loss
Caloric deficit deepens as appetite suppression becomes consistent. Most researchers report 2–4% body weight reduction by week 6.
Compound effect
Glucagon-driven thermogenesis adds to GLP-1 suppression. Dose escalation here is common if tolerating well. Phase II showed strongest change at weeks 8–24.
Peak outcome window
Eli Lilly Phase II data showed mean 24.2% body weight reduction at 48 weeks with 12 mg/week. Plateaus are normal and do not indicate treatment failure.
Retatrutide is a fatty-acid-modified peptide that binds to and activates all three receptors with balanced potency. The design challenge — and key innovation — was tuning glucagon receptor activity so that its hyperglycaemic potential is offset by the insulin-stimulating effects of GLP-1 co-activation.
GLP-1R activation
GIPR activation
GCGR activation
| Week | Dose | Frequency |
|---|---|---|
| 1–2 | 2 mg | Once weekly |
| 3–4 | 4 mg | Once weekly |
| 5–8 | 6–8 mg | Once weekly |
| 9–24 | 8–12 mg | Once weekly |
| Off | — | 4–8 weeks |
Reconstitution: Use bacteriostatic water. For a 10 mg vial + 2 mL BAC water, each 0.2 mL (20 units on an insulin syringe) = 1 mg. Use the Reconstitution Calculator → for exact units.
Most common during dose escalation. Usually resolves within 2–3 weeks at a stable dose. Eating smaller, low-fat meals helps.
Linked to nausea. Slow dose escalation is the most effective prevention strategy.
GI motility changes from GLP-1 activity. Stay hydrated. Usually transient.
The intended mechanism. Can become excessive — ensure adequate protein intake (≥1.6 g/kg).
Redness, small lump, or mild pain at injection site. Rotate sites every dose.
Often secondary to reduced caloric intake. Ensure carbohydrate intake is not dangerously low.
Glucagon receptor activity can mildly elevate resting heart rate. Monitor. Discontinue if sustained >100 bpm at rest.
More likely if used alongside insulin sensitisers. Monitor blood glucose, especially in the first weeks.
Given the glucagon component's effect on hepatic glucose output and the GLP-1 component's insulin-modulating activity, monitoring is important for any protocol beyond a short-duration study.
Baseline (before)
Fasting glucose, HbA1c, lipid panel, liver enzymes (ALT/AST/GGT), amylase, lipase, thyroid panel (TSH/T4), full blood count
Week 8
Fasting glucose, liver enzymes, amylase. Assess for any pancreatitis indicators.
Week 24
Full panel repeat. Assess body composition change relative to dose. Check heart rate trend.
Off-cycle
Full repeat. Confirm liver enzyme normalisation. Reassess metabolic markers to measure net benefit.
Starting too high
Fix: GI side effects dominate at high starting doses. Begin at 2 mg and escalate no faster than every 2 weeks.
Skipping dose escalation
Fix: Jumping straight to 6–8 mg causes severe nausea and often forces discontinuation. The escalation schedule exists for a reason.
Insufficient protein intake
Fix: Appetite suppression can drop total calories dangerously low. Ensure ≥1.6 g protein per kg of bodyweight to preserve lean mass.
Not rotating injection sites
Fix: Using the same site causes lipohypertrophy and impairs peptide absorption. Rotate among abdomen quadrants and thighs.
Storing reconstituted vials too long
Fix: Reconstituted peptide degrades. Use within 28 days refrigerated. Label vials with reconstitution date.
Stacking with semaglutide or tirzepatide
Fix: Compounding GLP-1 activity significantly worsens GI side effects. Use retatrutide as a standalone GLP-1 axis agonist.
Insulin / Insulin secretagogues
Combined hypoglycaemic effect. Monitor blood glucose closely.
Oral medications (narrow therapeutic index)
Delayed gastric emptying affects absorption timing of many oral drugs. Consult a pharmacist.
Warfarin / Anticoagulants
Altered absorption kinetics. Monitor INR more frequently during escalation.
Other GLP-1 agonists
Additive GI effects. Do not use concurrently.
Metformin
Generally well tolerated together. GI effects may compound.
Thyroid medications
Monitor TSH — GLP-1 agonists have shown rodent thyroid effects. Clinical significance unclear.
The sections below contain our original preclinical research overview — covering key findings from animal models, the scientific introduction, and research applications.
Ready to research?
Research-grade lyophilised powder. Third-party COA verified. Fast AU shipping.