Retatrutide Dose: What the Trials Used, 1 mg to 12 mg a Week

No dose of retatrutide is approved. The FDA alert on unapproved GLP-1 drugs (updated September 1, 2026) says retatrutide is not a component of any approved drug, has not been found safe and effective for any condition, and cannot be used in compounding under federal law.1 The doses come from trials, once a week: 1, 4, 8 or 12 mg in the phase 2 obesity trial (NEJM, 2023) and 4, 9 or 12 mg in the phase 3 TRANSCEND-T2D-1 trial in type 2 diabetes (The Lancet, June 2026).2,3

The table draws on the phase 2 abstract (NEJM, 2023), the TRANSCEND-T2D-1 abstract (The Lancet, June 2026) and the TRIUMPH-1 registry record (ClinicalTrials.gov, August 2026).2,3,4

TRIUMPH-1 runs 80 weeks against placebo, and then participants receive retatrutide for a further 24 weeks (ClinicalTrials.gov record, August 2026).4

What retatrutide is, and when it may reach the market, is on the retatrutide explainer.

Retatrutide has no approved starting dose. In the phase 2 obesity trial (NEJM, 2023; 338 adults with obesity and no diabetes), the groups that reached 4 mg or 8 mg a week each split into a 2 mg start and a 4 mg start, and the 12 mg group started at 2 mg.2 The lower 2 mg starting dose partially reduced gastrointestinal adverse events compared with a 4 mg starting dose.2

In that trial, the most common adverse events in the retatrutide groups were gastrointestinal; they were dose-related and mostly mild to moderate in severity (NEJM, 2023).2

In TRANSCEND-T2D-1, the phase 3 trial of 537 adults with type 2 diabetes published in The Lancet on June 13, 2026, body weight fell 11.5% on weekly retatrutide 4 mg, 13.9% on 9 mg and 15.3% on 12 mg over 40 weeks, versus 2.6% on placebo, counting everyone who started (the treatment regimen estimand).3 Between 2% and 5% of people on retatrutide stopped study treatment because of adverse events, versus 0% on placebo.3

The table draws on the TRANSCEND-T2D-1 abstract (The Lancet, June 2026); each row counts everyone who started, over 40 weeks.3

The TRANSCEND-T2D-1 numbers come from adults with type 2 diabetes, not from adults with obesity alone.

Retatrutide is dosed once a week in its trials, not once a day. TRANSCEND-T2D-1 (The Lancet, June 2026) gave 537 adults with type 2 diabetes retatrutide 4 mg, 9 mg or 12 mg, or placebo, by once-weekly subcutaneous injection.3 TRIUMPH-1, Lilly's phase 3 master protocol in adults without type 2 diabetes who have obesity or overweight, also gives retatrutide (LY3437943) once weekly under the skin (ClinicalTrials.gov record, August 2026).4 The phase 2 obesity trial gave every dose once weekly too (NEJM, 2023).2

There is no 30 mg retatrutide dose in the published trials; 12 mg a week is the highest dose in both. The phase 2 trial (NEJM, 2023) tested 1, 4, 8 and 12 mg weekly in 338 adults with obesity, and TRANSCEND-T2D-1 (The Lancet, June 2026) tested 4, 9 and 12 mg weekly in 537 adults with type 2 diabetes.2,3 The FDA has warned companies that sold unapproved retatrutide labeled "for research purposes" or "not for human consumption" directly to consumers with dosing instructions (alert updated September 1, 2026).1

This article is for information only and is not medical advice. Talk to a licensed clinician before you start, change or stop a medicine.