Retatrutide
Weight Loss, Metabolic Health
In short
- A triple agonist at the GIP, GLP-1, and glucagon receptors — the glucagon arm is what distinguishes it from tirzepatide and semaglutide.
- Phase 2 results reported roughly 24% mean weight reduction at 48 weeks, the largest figure published for any pharmacological agent to date.
- Still investigational. Phase 3 (TRIUMPH) is ongoing and it is NOT approved anywhere.
- Everything sold as retatrutide today is grey-market, unverified, and made outside the manufacturer's supply chain.
- Because it is unapproved, no label, no verified purity standard, and no established human dosing schedule exist outside the trials.
Structure
A 39-amino-acid triple agonist peptide. PubChem has no entry under this name, and peptides of this size are represented by sequence rather than a small-molecule structure diagram.
How it works
Retatrutide activates three receptors. GLP-1 and GIP agonism supply the familiar incretin effects — glucose-dependent insulin secretion, glucagon suppression, delayed gastric emptying, reduced appetite.
The glucagon receptor arm is the novel component and is counterintuitive: glucagon raises blood glucose, which would seem to work against the goal. The rationale is that glucagon receptor agonism increases energy expenditure and promotes hepatic fat oxidation, and that the GLP-1 component offsets the glycaemic effect. Increasing energy output alongside reducing intake is the proposed explanation for the larger weight reductions.
What the research shows
The phase 2 trial reported mean weight reduction of about 17.5% at 24 weeks and 24.2% at 48 weeks at the highest dose, exceeding published figures for semaglutide and tirzepatide.
Reductions in hepatic fat content were also reported, consistent with the glucagon mechanism.
These are phase 2 findings in a controlled population. Phase 3 has not reported, and phase 2 results routinely attenuate at phase 3.
Dosing in the literature
Figures below are quoted from published studies, with the species or population they were measured in. They are records of what was studied, not recommendations.
| Studied in | Amount | Route | Source |
|---|---|---|---|
| Human — phase 2 obesity trial, titrated over 48 weeks | Escalated to 1, 4, 8, or 12 mg weekly | subcutaneous | PubMed |
Commonly reported ranges
These are amounts people report using. They are not from any study, have not been evaluated for safety, and are reproduced here only because they circulate widely and are better seen alongside the evidence than instead of it.
| Reported by | Amount | Route |
|---|---|---|
| Commonly reported, mirroring the trial titration | 2–12 mg weekly, escalated slowly | subcutaneous |
No published human pharmacokinetic study establishes a dose, interval, or duration for this compound. Community figures below have no trial behind them and are reports of practice, not evidence. More importantly: there is no approved product, so anything obtained is of unverified identity, purity, and concentration. Community protocols copy the trial titration, but a trial dose assumes the trial's drug — reconstituting an unverified powder and assuming milligram accuracy is where the actual risk sits, not in the schedule.
Handling and storage
Supplied as a lyophilised powder requiring reconstitution with bacteriostatic water. The powder is comparatively stable; once reconstituted it is refrigerated and used within weeks. Track the date you reconstitute each vial — the Inventory section does this, and it is the difference between knowing a vial is three weeks old and guessing.
Weekly subcutaneous injection with slow titration is the pattern from the trial. The gastrointestinal effects are dose-limiting and are the practical constraint on escalation speed.
Side effects
Nausea, vomiting, diarrhoea, and constipation dominate the side-effect profile across this entire class. They are dose-related, worst after each escalation, and are the reason titration schedules exist. Serious but uncommon events include pancreatitis and gallbladder disease, the latter more likely with rapid weight loss. Delayed gastric emptying is now addressed in pre-operative anaesthesia guidance because of aspiration risk from retained stomach contents.
Retatrutide adds a glucagon-mediated consideration: dose-dependent increases in heart rate were reported in phase 2, and the glucagon arm has theoretical implications for glycaemic control that phase 3 is intended to characterise.
Weight regain after discontinuation is consistent across this class and is not a failure of the drug — appetite regulation returns to baseline when the receptor stops being activated. Any decision to start should account for what stopping looks like.
Because there is no approved product, the additional and unquantifiable risk is what is actually in the vial.
Combinations
Combining with any other incretin agonist duplicates two of the three receptor targets and compounds gastrointestinal effects without evidence of benefit.
With insulin or sulfonylureas, hypoglycaemia risk rises and those agents typically need reducing — a real interaction across this class.
Research status
Phase 2 results were published in the New England Journal of Medicine in 2023. The phase 3 TRIUMPH programme in obesity and related conditions is ongoing.
The underlying science is legitimate and conducted by Eli Lilly. What does not exist is a completed phase 3, an approval, or a legitimate consumer supply.
Legal status
Not approved in any jurisdiction. Investigational. Sale for human consumption is unlawful in most countries, and everything on the grey market is manufactured outside any regulated supply chain.
WADA status
Not specifically named on the Prohibited List. Falls under WADA class S0, which prohibits any pharmacological substance not currently approved by any governmental regulatory health authority for human therapeutic use. Treat it as prohibited in sport.
Conclusion
Retatrutide has produced the most striking phase 2 weight-loss data published, and it is the compound in this library where the gap between the science and the supply chain is widest.
The molecule is real and promising. The vial you can buy is not the molecule Lilly studied, and no test you can run at home establishes that it is.
Sources
- [1]Retatrutide phase 2 trial in obesity (NEJM, 2023)PubMed
- [2]Retatrutide (LY3437943) pharmacologyPubMed
- [3]TRIUMPH phase 3 programmeClinicalTrials.gov
- [4]WADA Prohibited List (current)WADA
Track your own Retatrutide protocol
Peppers logs your doses, models your levels from this half-life, tracks your vials and tells you when you will run out. Free on iPhone.
Reference and educational information only. Not medical advice. Nothing here diagnoses, treats, or prescribes, and nothing here is a recommendation to use any compound. The compounds described are research chemicals and are not approved for human consumption. Legal and anti-doping status change — the review date above is when these claims were last checked. Talk to a qualified clinician about anything you intend to take.