Retatrutide dosage chart: the published trial schedules

Retatrutide is an investigational once-weekly agonist of the GIP, GLP-1 and glucagon receptors. It has no FDA label, so there is no approved dosage. What exists are the dose ladders Eli Lilly used in its trials. This chart collects them in one place, with the week each step began and the results each arm reported. For the drug’s background and status, see the retatrutide hub.

Phase 3 dose ladders (TRIUMPH and TRANSCEND)

Every Phase 3 arm began at 2 mg once weekly, and the dose was increased every four weeks until it reached the arm’s target (Eli Lilly, Dec 11, 2025). The program used five dose strengths: 2, 4, 6, 9 and 12 mg (Eli Lilly, May 21, 2026).

TRIUMPH-1 and TRIUMPH-2 randomized participants to 4, 9 or 12 mg or placebo; TRIUMPH-3 and TRIUMPH-4 tested only 9 and 12 mg (Eli Lilly, Dec 11, 2025). TRANSCEND-T2D-1, in 537 people with type 2 diabetes, used 4, 9 and 12 mg over 40 weeks (Eli Lilly, Mar 19, 2026). One wording difference: Lilly’s July 23, 2026 release describes the 4 mg arm as reached “via steps at 2 mg and 4 mg”, while other releases say “one step at 2 mg”. Both describe the same schedule: 2 mg for 4 weeks, then 4 mg (Eli Lilly, Jul 23, 2026).

• Weekly dose (published steps)
• Modeled amount (mg-eq)
• Stable window

The chart plots the 12 mg arm’s steps above a modeled relative amount in the body. The curve is a one-compartment estimate with a 6-day half-life, not a measured plasma level; the half-life guide explains the math.

The first 12 mg dose: a dated example

Trial reports count in weeks. To turn weeks into calendar dates, add 28 days per completed step. With a Monday, Jan 5, 2026 start, the 12 mg arm’s schedule falls on these dates.

Week 17 begins 112 days after week 1 (16 weeks × 7 days), which is Apr 27, 2026. The 9 mg step would have begun on Mar 30, 2026 (week 13), and the 4 mg arm would have reached its target on Feb 2, 2026 (week 5). The titration calculator does this date arithmetic for any start date and any of the published ladders, and the dose-level plotter draws the modeled curve. The full 12 mg arm record is on the TRIUMPH 12 mg protocol page.

Phase 2 obesity ladders (NCT04881760)

The 48-week Phase 2 obesity trial enrolled 338 adults and randomized them 2:1:1:1:1:2:2 across six retatrutide arms and placebo (N Engl J Med, Jun 26, 2023). Its protocol increased doses “at 4-week increments” until the maintenance dose (Eli Lilly, hosted on ClinicalTrials.gov, Aug 29, 2022). Two arms each for 4 mg and 8 mg differed only in starting dose: 2 mg or 4 mg.

Weight values are least-squares mean percent change from baseline as posted on ClinicalTrials.gov (ClinicalTrials.gov, Sep 13, 2023). They match the NEJM paper, which pooled the paired arms: −17.1% for both 4 mg arms, −22.8% for both 8 mg arms and −24.2% for 12 mg, against −2.1% on placebo at week 48 (N Engl J Med, Jun 26, 2023). Nausea counts come from the registry’s non-serious adverse event table, which lists terms reported by at least 5% of an arm through up to 52 weeks; the percentages are our arithmetic from the posted counts.

Starting dose and nausea: the 2 mg vs 4 mg contrast

The Phase 2 design let researchers compare the same maintenance dose with two different starting doses. The difference in nausea was large:

• 8 mg arms: 60.0% of participants reported nausea with a 4 mg start, against 17.1% with a 2 mg start.
• 4 mg arms: 36.4% with a 4 mg start (no escalation), against 18.2% with a 2 mg start.

The NEJM authors wrote that gastrointestinal events were dose-related, mostly mild to moderate, and “partially mitigated with a lower starting dose (2 mg vs. 4 mg)” (N Engl J Med, Jun 26, 2023). Every Phase 3 arm then began at 2 mg. The arms were small (33 to 35 participants each), so treat the percentages as estimates with wide uncertainty.

Phase 2 type 2 diabetes ladders (NCT04867785)

A parallel Phase 2 trial in 281 adults with type 2 diabetes tested six retatrutide arms against placebo and dulaglutide 1.5 mg, with HbA1c at 24 weeks as the primary endpoint and follow-up to 36 weeks (The Lancet, Jun 26, 2023). Its protocol also stepped doses at 4-week increments (Eli Lilly, hosted on ClinicalTrials.gov, Aug 29, 2022).

HbA1c values are least-squares mean changes in percentage points. Mild-to-moderate gastrointestinal events occurred in 35% of all retatrutide participants (67 of 190), ranging from 13% at 0.5 mg to 50% with the rapid 8 mg escalation; placebo was 13% (The Lancet, Jun 26, 2023).

Why “2 → 4 → 8 → 12” is not the Phase 3 ladder

Many dosing charts online print 2 → 4 → 8 → 12 mg as “the” retatrutide schedule. That is the 12 mg ladder from the Phase 2 obesity trial, published in 2023. Phase 3 dropped the 8 mg step and added 6 mg and 9 mg, which adds one more 4-week step before 12 mg.

The cumulative totals are arithmetic: 4 × (2 + 4 + 8 + 12) = 104 mg for Phase 2, and 4 × (2 + 4 + 6 + 9) = 84 mg for Phase 3. The Phase 3 ladder reaches 12 mg four weeks later and with 20 mg less given over the first 16 weeks. The Phase 2 version has its own page at /protocols/retatrutide-phase2-12mg/. Earlier still, the Phase 1b trial’s top cohort escalated 3 → 6 → 9 → 12 mg within 12 weeks and lost 8.96 kg more than placebo by week 12 (The Lancet, Oct 27, 2022).

Results by Phase 3 arm (TRIUMPH-1, 80 weeks)

TRIUMPH-1 randomized 2,339 adults with obesity or overweight and at least one weight-related condition, without diabetes, 1:1:1:1 to 4, 9 or 12 mg or placebo. Average baseline weight was 112.7 kg (Eli Lilly, May 21, 2026). Lilly’s release leads with the efficacy estimand (the effect if everyone had stayed on treatment); the NEJM paper leads with the treatment-regimen estimand, which counts everyone regardless of adherence (N Engl J Med, Sep 29, 2026).

At 12 mg, 62.5% of participants reached at least 25% weight loss under the efficacy estimand, against 2.2% on placebo (Eli Lilly, May 21, 2026). Phase 2 and Phase 3 results are not directly comparable: the trials differ in population, duration (48 vs 80 weeks) and analysis. More results by trial are in the trial results guide, and adverse events are covered in the side effects guide.

“GLP-3”, “reta” and legal status

“Reta” is shorthand for retatrutide, and “GLP-3” is a street or marketing name, not a scientific term. An FDA warning letter dated Aug 24, 2026 cites a seller marketing retatrutide as “GLP-3R” and calls it an unapproved new drug (FDA, Aug 24, 2026). Lilly said on Aug 12, 2026 that no retatrutide medicine has been approved by any regulator (Eli Lilly, Aug 12, 2026), and on Sep 29, 2026 it said it plans a U.S. BLA submission in Q1 2027 (Eli Lilly, Sep 29, 2026). Retatrutide is legally available only to participants in Lilly clinical trials.

The ladders on this page describe how the trials were run. They are reported as published facts for research and education, not as a schedule for anyone to follow. To convert any step to a unit reading at a given lab concentration, see the units calculator and the units chart.