Retatrutide (development code LY3437943) is an investigational peptide made by Eli Lilly that acts on three hormone receptors at once: GIP, GLP-1, and glucagon. It is being studied in clinical trials for obesity and type 2 diabetes. It is not FDA-approved and is not available as a prescription medicine.

Is retatrutide FDA-approved?

No. As of mid-2026 retatrutide is investigational and has not been approved by the FDA or any major regulator. It is only available to people enrolled in registered clinical trials. Powders sold online as 'research chemicals' are not the trial product and are not approved or quality-assured for human use.

What is retatrutide being studied for?

Published phase 2 trials examined retatrutide for weight reduction in obesity, glycemic control in type 2 diabetes, and metabolic dysfunction-associated steatotic liver disease (MASLD/fatty liver). Phase 3 trials (the TRIUMPH program) are under way, and the first pivotal obesity trial has reported positive top-line results. None of these uses is FDA-approved.

How is retatrutide different from semaglutide or tirzepatide?

Semaglutide targets one receptor (GLP-1) and tirzepatide targets two (GIP and GLP-1). Retatrutide adds a third — the glucagon receptor — which in animal studies increases energy expenditure. Whether this translates into a meaningful long-term advantage in people is still being tested; it is not yet an approved drug.

What are the reported side effects of retatrutide?

In phase 2 trials the most common adverse events were gastrointestinal (nausea, vomiting, diarrhea, constipation), mostly mild to moderate and dose-related. Dose-dependent increases in heart rate were also observed. Long-term safety is not established, and a clinician is the right person to assess risk.

Is retatrutide legal to buy?

Retatrutide is not an approved medicine, so it cannot be legally prescribed or sold for human use. Vendors that sell it label it 'for research use only,' which does not make it safe or legal to inject. Buying or self-administering an unapproved drug carries legal, quality, and health risks. WikiPeps does not sell it or say where to get it.

Does WikiPeps provide a retatrutide dose?

No. There is no validated human dose outside of clinical trials, and WikiPeps does not publish dosing protocols or amounts for any peptide. Any decision about an investigational drug belongs with a licensed clinician and, ideally, enrollment in a monitored trial.

Weight & metabolism · Dosage

Retatrutide dosage

Retatrutide comes in 6 mg and 12 mg vials. Pick your vial to see exactly how much bacteriostatic water to add and how many insulin units to draw. Reconstitution math for the 6 mg and 12 mg vials. Retatrutide is investigational (not approved); published phase 2 trials studied once-weekly SC doses of 1–12 mg — shown for reference, not as a recommended dose.

6mg

At 3 mL water: 2 mg/mL
Per unit: 20 mcg

See the 6 mg card

12mg

At 3 mL water: 4 mg/mL
Per unit: 40 mcg

See the 12 mg card

Calculate for your vial

Enter the mg on your Retatrutide vial, the bacteriostatic water you added, and your target dose — it works out the exact units to draw on a U-100 insulin syringe, for whatever you personally have.

Reconstitution Calculator

200 units exceeds one U-100 syringe — add more water to lower the concentration.

Units to draw (U-100)200units

Volume to draw2mL

Concentration2mg/mL

Per insulin unit20mcg

Doses per vial1.5doses

Check the decimal. A misplaced decimal point here is a 10× dosing error. Re-read every number, and confirm your dose with a licensed clinician before you draw.

Educational only — not a dosing recommendation. This tool does the measurement math; it does not tell you what to take. On a U-100 insulin syringe, 100 units = 1 mL.

Dosing schedule

Retatrutide · fixed weekly step-up schedule

Optional

An investigational trial titration. Everyone escalated on a fixed schedule; heavier / more-tolerant participants reached the higher 8–12 mg targets that produced the greatest weight loss.

12–4 mg/wkWeeks 1–4Trial starting dose
2+2–4 mg every 4 wksEscalationToward assigned target
38 mg/wkTarget group
412 mg/wkHighest studied~24% mean loss at 48 wk

Retatrutide is investigational and not FDA-approved. In the trial, participants did not dose by body weight — they escalated on a fixed every-4-weeks schedule toward an assigned target (1, 4, 8 or 12 mg), with the highest targets producing the greatest weight loss. Any real-world use belongs entirely with a licensed clinician.

Source: Jastreboff et al., NEJM 2023 (NCT04881760) — investigational, NOT FDA-approved. Educational only — not medical advice and not a dosing recommendation. Any dosing decision belongs with a licensed clinician.

Reconstitution figures are deterministic measurement math. WikiPeps is a community reference and sells injection supplies only — never peptides. Nothing here is medical advice.