Retatrutide: dosage

This page gives no doses, and that is deliberate. There is no approved retatrutide medicine to take a dose from: Lilly states that “no retatrutide medicine has yet been approved by FDA or any other regulatory agency in the world”.[1]

What is in the vial is unknown

The FDA says of unapproved GLP-1 products sold online: “These products have been sold directly to consumers for human use with dosing instructions”. It warns that they “could contain too little, too much or no active ingredient at all”.[2] Independent testing points the same way. ABC News reported that one laboratory said “it has tested 18 samples of counterfeit retatrutide this year with only one matching its label claim”: “about 30 percent had higher concentrations and about 30 percent had lower concentrations, while one vial contained none of the peptide”.[3] The researchers concluded that “inaccurate dosing alone may represent an important source of risk”.[3] In its lawsuits, Lilly alleges that sellers' products have shown “incorrect dosages ranging from zero to overdoses” and even “completely different active ingredients such as insulin, which could be life-threatening”; these are Lilly's allegations, made as a party to the cases.[4]

The practical consequence is that there is no reference point. The strength on a label may be wrong in either direction, as that testing found. For someone who goes ahead regardless, the only controls left are never using alone, having someone nearby who knows what was taken, and stopping at the first warning sign below. The FDA's injection advice also applies: “Always use a new, sterile needle and syringe for each dose”.[2]

What the trial reported about side effects

In the phase 2 trial, “The most common adverse events in the retatrutide groups were gastrointestinal”, and the investigators reported that these were “partially mitigated with a lower starting dose”.[5] That finding is about trial participants, not guidance for anyone else. America's Poison Centers notes that with GLP-1 drugs, “In severe cases, dehydration or hypoglycemia” can occur.[6]

Warning signs

Victoria's health department, in its alert on toxicity linked to products labelled retatrutide, lists the symptoms to watch for: “tiredness, abdominal pain, itchy skin, dark urine, yellow eyes or skin and easy bruising”.[7] Those symptoms, or signs of the dehydration and low blood sugar the poison centres warn of, are reasons to get medical help and to bring the product with you.[6]

Read more on this site

• Retatrutide from a research vial: what the trials found, what tested vials held, and the warning signs.

References

1. Eli Lilly and Company v. American Peptides LLC, No. 5:26-cv-04146 (W.D. La.), Complaint, filed 10/08/26 — US District Court, via CourtListener RECAP
2. FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss (content current as of 10/01/2026), Wayback capture of 19 October 2026 — US Food and Drug Administration
3. New testing of black-market peptides reveals dangerous dosing levels (Rachel Carbonell, Caitlyn Gribbin and Andi Yu for ABC News, 28 August 2026) — RNZ
4. Lilly sues over 'illegal sales' of obesity drug retatrutide (August 2026) — pharmaphorum
5. Triple-Hormone-Receptor Agonist Retatrutide for Obesity: A Phase 2 Trial (Jastreboff et al., N Engl J Med 2023;389:514-526) — PubMed (New England Journal of Medicine)
6. GLP-1 (Track Emerging Hazards) — America's Poison Centers
7. Toxicity linked to unapproved peptide product labelled Retatrutide (health alert, 19 June 2026) — Department of Health, Victoria, Australia