Retatrutide (5mg)

Retatrutide 5mg — Triple GLP-1/GIP/Glucagon Receptor Research Peptide

Retatrutide, developed under the code name LY3437943 (also written LY-3437943), is a 39-amino-acid peptide engineered by Eli Lilly as a triple agonist of the GLP-1, GIP and glucagon receptors. It is commonly searched as retatrutide, the reta peptide, or simply reta. Its GIP-based backbone carries a fatty-acid side chain that binds reversibly to serum albumin, extending its half-life enough to support once-weekly dosing in research protocols, which is the same lipidation strategy used in other long-acting incretin peptides.

This page is the 5mg vial, the smallest and lowest-cost entry point into retatrutide research, suited to a first pilot study, a dose-response titration series, or confirming a model before committing to a larger batch. Omega Peptides Australia's most established retatrutide listing is the 10mg vial, which also carries 20mg, 30mg, 60mg and Box options if you'd rather choose your size from one page.

Omega Peptides Australia supplies this 5mg vial as a high-purity (≥99% HPLC), COA-verified lyophilised powder. Orders placed before 12pm are dispatched the same day from within Australia, and the certificate for every batch is published in our COA library.

Key research areas

• Triple receptor agonism. Retatrutide is studied as the first clinical-stage peptide to activate all three major incretin/glucagon receptors at once: GLP-1R, GIP receptor (GIPR) and the glucagon receptor (GCGR). Researchers use it to compare single, dual and triple agonist mechanisms within the same experimental model.
• Body weight and energy expenditure. The added glucagon receptor activity is of particular research interest because glucagon signalling increases hepatic energy expenditure and lipolysis independently of appetite suppression, a mechanism not present in GLP-1-only or GLP-1/GIP dual agonists such as semaglutide or tirzepatide.
• Phase 3 clinical data (TRIUMPH program). Retatrutide has progressed through Eli Lilly's Phase 3 TRIUMPH program, including the TRIUMPH-1 and TRIUMPH-3 trials, which reached primary completion in April 2026. Published trial data has reported weight reductions in the order of 15 to 24 percent over 48 to 72 weeks, with some reports of up to roughly 28 percent at 80 weeks in extended dosing arms.
• Glycaemic control research. As with other incretin-based peptides, retatrutide is studied for its effect on insulin secretion, glucagon suppression in the fed state and glucose-dependent insulinotropic activity, with a comparatively low reported risk of hypoglycaemia in trial data.
• Comparative incretin pharmacology. Because retatrutide, tirzepatide and semaglutide activate overlapping but distinct receptor combinations, researchers use all three as comparator compounds to isolate which receptor pathway drives a particular metabolic outcome.
• Tolerability profile. Gastrointestinal effects, including nausea and diarrhoea, are the most commonly reported adverse findings in trial data, consistent with the class-wide GI effects seen across incretin receptor agonists, and are studied alongside dose-escalation protocols intended to improve tolerability.

How retatrutide works

Retatrutide's peptide backbone is derived from GIP and engineered to also bind and activate the GLP-1 and glucagon receptors, making it a unimolecular triple agonist rather than a mixture of separate compounds. Activating GLP-1R and GIPR together enhances glucose-dependent insulin secretion and appetite suppression, the same mechanism exploited by dual agonists like tirzepatide. The addition of GCGR activity is what differentiates retatrutide: glucagon receptor signalling in the liver increases fatty acid oxidation and resting energy expenditure, an effect that in principle adds a metabolic-rate component on top of the appetite and insulin effects shared with dual and single agonists.

Like other long-acting incretin peptides, retatrutide carries a fatty diacid side chain attached via a linker to a lysine residue in its backbone. This lipidation allows the peptide to bind reversibly to circulating albumin, which slows renal clearance and extends its plasma half-life to a point that supports once-weekly administration in clinical dosing protocols, rather than the multiple-times-daily dosing needed for earlier incretin peptides without this modification.

Specifications

5mg vial: pricing and who it suits

The 5mg vial is $99.99, about $20.00 per mg. It's the lowest-commitment way to start a retatrutide research protocol: enough material for a short pilot, an initial dose-response series, or confirming assay conditions before scaling to a larger batch. It comes from the same COA-verified production batches as every other size, so purity and identity are identical between vials; only the amount of peptide differs.

If your protocol is already validated and you know you'll need more material across a longer study, the per-mg cost drops significantly at larger sizes such as the 30mg or 60mg vial.

Quality and COA verification

Every batch of Retatrutide is independently tested by Janoshik Analytical. HPLC confirms purity of 99 percent or higher and mass spectrometry confirms that the measured mass matches the expected molecular weight of the 39-residue backbone, verifying identity as well as purity. A Certificate of Analysis is issued for every batch and published in our COA library, where the batch number on the vial can be matched to its report. Vials are lyophilised and sealed under sterile conditions to protect long-term stability, and orders are packed for domestic transit and shipped from Australian stock.

Frequently bought together

• Bacteriostatic Water (10mL) — $29.99, the standard diluent for reconstituting lyophilised peptides.
• Tirzepatide — a dual GLP-1/GIP receptor agonist, often studied alongside retatrutide as a comparator compound.
• Retatrutide Starter Kit — a bundled option for researchers setting up a full protocol from scratch.

Purchase other quantities

Retatrutide is available in several sizes across our store. The 5mg vial on this page is the smallest option; for 10mg, 20mg, 30mg, 60mg or the bulk Box option, see the links below.

• Retatrutide (10mg and other sizes) — our main Retatrutide listing, including the Box (10mg x10) option
• Retatrutide 20mg
• Retatrutide 30mg
• Retatrutide 60mg

Research guides

• Retatrutide research guide
• Best place to buy Retatrutide in Australia
• Retatrutide vs Tirzepatide
• Retatrutide Premium Kit
• Peptide reconstitution calculator

Frequently asked questions

What is reta?
Reta is the shorthand researchers use for retatrutide, a 39-amino-acid peptide developed by Eli Lilly under the code name LY3437943. Searches for reta, the reta peptide and retatrutide all refer to the same compound. Omega Peptides Australia supplies it as a lyophilised research peptide in 5mg, 10mg, 20mg, 30mg and 60mg vials for laboratory use only.

What is retatrutide?
Retatrutide is a triple receptor agonist that activates the GLP-1, GIP and glucagon receptors from a single peptide backbone. It is studied in metabolic research for its effects on body weight, energy expenditure and glycaemic control, and has progressed through Eli Lilly's Phase 3 TRIUMPH clinical program.

What is retatrutide also known as?
Retatrutide's development code name is LY3437943, sometimes written LY-3437943. It is also referred to as reta or the reta peptide in research shorthand.

Can I buy retatrutide at Chemist Warehouse or a pharmacy in Australia?
No. Retatrutide is not a registered medicine in Australia and is not listed on the Australian Register of Therapeutic Goods, so it is not stocked by Chemist Warehouse, Priceline or other retail pharmacies. Omega Peptides Australia supplies retatrutide only as a research-grade lyophilised compound for in-vitro laboratory work.

Can Australian compounding pharmacies supply retatrutide?
Compounding pharmacies in Australia may only prepare a medicine for an individual patient on a prescription from a registered practitioner, and the TGA has warned about the uncertainties of compounded unapproved peptide products. Retatrutide is not an approved ingredient. Research suppliers such as Omega Peptides Australia supply the lyophilised research compound for laboratory use, which is a separate pathway from pharmacy compounding.

How does retatrutide work?
Retatrutide activates three receptors from one peptide backbone: GLP-1R and GIPR, which together drive glucose-dependent insulin secretion and appetite suppression, and the glucagon receptor (GCGR), which increases hepatic fatty acid oxidation and energy expenditure. A fatty-acid side chain allows the peptide to bind reversibly to albumin, extending its half-life to support once-weekly dosing in research protocols.

What does the research show about retatrutide?
Retatrutide has been evaluated in Eli Lilly's Phase 3 TRIUMPH program, including the TRIUMPH-1 and TRIUMPH-3 trials, which reached primary completion in April 2026. Reported trial data has shown weight reductions in the order of 15 to 24 percent over 48 to 72 weeks, with some extended dosing arms reporting up to roughly 28 percent at 80 weeks. The most commonly reported adverse effects are gastrointestinal, including nausea and diarrhoea, with a comparatively low reported risk of hypoglycaemia.

Why choose the 5mg vial instead of a larger size?
The 5mg vial is the lowest-cost way to start a retatrutide protocol, ideal for a first pilot, a dose-response series, or confirming a model before scaling up. It comes from the same COA-verified batches as every other size Omega Peptides Australia stocks, so purity and identity don't change between sizes, only the amount of peptide per vial.

How do you reconstitute retatrutide?
Add bacteriostatic water slowly down the inside wall of the vial so it runs onto the powder gently, then swirl gently until the solution is clear. Do not shake the vial. The reconstitution calculator gives the volume needed for a chosen concentration. Once reconstituted, keep the vial refrigerated at 2–8°C and use within 28 days.

How should retatrutide be stored?
Store the sealed lyophilised powder at 2–8°C for short-term use or at −20°C for long-term storage, protected from light and moisture, and avoid repeated freeze-thaw cycles. After reconstitution, refrigerate at 2–8°C and use within 28 days.

Where can I buy retatrutide in Australia?
Omega Peptides Australia holds retatrutide in domestic stock and dispatches orders placed before 12pm on the same business day. Every batch is COA-verified by an independent laboratory and the certificates are published online. Order this 5mg vial here, or see our main Retatrutide listing for 10mg, 20mg, 30mg, 60mg and Box options.

What does this 5mg vial of retatrutide cost in Australia?
This 5mg vial is $99.99, about $20.00 per mg. Larger sizes reduce the cost per mg significantly, down to roughly $9.83 per mg at the 60mg size. Bacteriostatic water for reconstitution is sold separately.

How do I get retatrutide online in Australia?
Add this 5mg vial to your cart and complete checkout. Orders are shipped with tracked domestic delivery in discreet, unbranded packaging. Orders placed before 12pm are dispatched the same business day from within Australia, and a tracking number is emailed once the parcel is lodged with the carrier.

Is retatrutide legal in Australia?
Omega Peptides Australia supplies retatrutide strictly for lawful in-vitro laboratory research. It is not approved by the TGA for human or veterinary use and is not sold as a medicine or supplement. Purchasers are responsible for ensuring their intended use complies with all applicable laws.

How does retatrutide differ from tirzepatide?
Tirzepatide is a dual agonist of the GLP-1 and GIP receptors. Retatrutide activates those same two receptors plus a third, the glucagon receptor, which adds a hepatic energy-expenditure mechanism not present in tirzepatide. Researchers often compare the two to separate the contribution of glucagon receptor signalling from GLP-1/GIP dual agonism. See our full Retatrutide vs Tirzepatide comparison for more detail.

⚠ For in-vitro research and laboratory use only. Not for human or veterinary use.