Frequently asked questions

What is retatrutide?

A synthetic peptide developed by Eli Lilly and Company under the code LY3437943, built from thirty-nine amino acid residues with three non-standard ones, a C-terminal amide, and a fatty-acid side chain on one lysine. It acts as an agonist at three receptors at once: the glucagon receptor, the glucose-dependent insulinotropic polypeptide receptor, and the glucagon-like peptide-1 receptor. source

Is retatrutide an approved medicine?

No, not in any country. FDA states that retatrutide is not a component of an FDA-approved drug and has not been found safe and effective for any condition. An independent peer-reviewed analysis describes it as not approved for therapeutic use in Australia or internationally. The sponsor has said it intends to file a US marketing application, but no application has been approved anywhere. source

Can a pharmacy compound it?

No. FDA's published position is that retatrutide "cannot be used in compounding under federal law". FDA also records warning telehealth companies for marketing it, active pharmaceutical ingredient distributors for selling it to compounders, and outsourcing facilities for repackaging it. This is a firmer position than the agency takes on substances it is still evaluating for the compounding bulks list. source

How is retatrutide different from a single or dual receptor agonist?

By the third receptor. Approved incretin products act at the GLP-1 receptor alone, or at the GIP and GLP-1 receptors together. Retatrutide adds agonism at the glucagon receptor. In the originating paper's animal work the authors attribute the extra effect on body weight to glucagon-receptor-mediated increases in energy expenditure layered on the reduction in calorie intake driven by the other two. That mechanistic account comes from mice, not from people. source

How large is the clinical trial programme?

Larger than for almost any compound in this category. The ClinicalTrials.gov registry returned 33 studies with retatrutide as an intervention on 2026-09-16 — fourteen phase 1, four phase 2, fourteen phase 3, and one expanded access record. Nearly all list Eli Lilly and Company as lead sponsor. Registered conditions include obesity, type 2 diabetes, knee osteoarthritis, obstructive sleep apnea, chronic kidney disease, cardiovascular disease and steatotic liver disease. source

If the trial evidence is that strong, why does this site make no claims?

Because the two questions are separate. The evidence describes what happened inside supervised trials using sponsor-manufactured material. Nothing in those trials examined material bought outside them, and no regulator anywhere has found the substance safe and effective for any condition. A published trial result is a record of that trial. It is not a product claim, and this site does not convert it into one. source

What is actually in products sold as retatrutide?

Almost nobody has checked. The only independent analysis located tested three products sold in Australia, all labelled as containing the same amount. All three did contain retatrutide, but the measured content ranged from about half the labelled amount to nearly double it. Metal and elemental impurities were below the thresholds the authors applied. Three samples is the entire published record, and the authors say so themselves. source

How should it be stored?

Nobody with the standing to say has said. There is no approved product label in any country and no pharmacopoeial monograph, so no manufacturer storage condition, in-use period or shelf life exists for this compound. FDA's published storage guidance for GLP-1 products concerns compounded drugs, and FDA states on the same page that retatrutide cannot lawfully be used in compounding at all, so that guidance does not reach it either. Any storage figure circulating for retatrutide traces back to a supplier page. source

Have the phase 3 results been peer reviewed?

Mostly not yet. One completed phase 3 trial, TRANSCEND-T2D-1, has been published in full in a peer-reviewed journal. The TRIUMPH obesity trials have so far been released as sponsor topline announcements and reported in the professional press, with detailed results promised at future meetings and in journals. None of the completed phase 3 studies had results posted on ClinicalTrials.gov when this entry was written. source

What did the trials report about side effects and people stopping?

Gastrointestinal events dominated across every trial, and the proportion of participants who stopped because of an adverse event rose with dose. In the published phase 3 diabetes trial, discontinuations owing to adverse events were reported as two to five per cent with retatrutide against none with placebo. In the announced phase 3 obesity results the rates were considerably higher at the top doses. The precise figures are recorded in the limitations and studies sections with their sources. source

Is it allowed in sport?

This site does not assert an answer, because no statement from an anti-doping authority naming retatrutide was located during data entry. What is on the record is that the United States Anti-Doping Agency publishes that GLP-1 agonists are not prohibited in sport and that the World Anti-Doping Agency is monitoring them — a statement that names only approved products, none of which is retatrutide. Reading that as covering an unapproved triple agonist would be an inference, not a finding. Ask your own anti-doping authority. source

Why do different sources give different molecular weights?

Partly because they are not always describing the same substance. FDA registers retatrutide and retatrutide sodium as two substances with different identifiers, and PubChem's record is titled as the sodium salt while carrying a formula with no sodium in it. An independent laboratory analysis reports a measured molecular weight for authentic retatrutide that differs slightly from the computed value. Both figures are on this page with their provenance stated rather than averaged into one. source