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Dosage information

Retatrutide dosage

No retatrutide dosage is approved or established for any person as of October 2026.12 Trials of repeated dosing gave it once a week under the skin, at 0.5 mg to 12 mg, for 12 to 80 weeks.34 Phase 3 trials used 4 mg, 9 mg or 12 mg.45 These are study doses, not guidance.

This page summarizes published sources for information only. It is not medical advice and does not tell anyone to use a product. Questions about your own health belong with a licensed clinician. For questions about an order or a product, contact us.

Is there an approved retatrutide dosage?

No. Retatrutide is a phase 3 investigational drug that no regulator has approved, so no label sets a dose for anyone.1 FDA states that it has not been found safe and effective for any condition.2 What exists instead are the doses tested in trials. Those trials used drug made by Lilly, given to adults who met each study's entry criteria.16 In the phase 1b and phase 2 trials, most higher doses were reached in steps from a lower starting dose.378 The figures below describe study conditions. They are not instructions for anyone.

Doses tested in clinical trials

Every trial below gave retatrutide to adults once a week by injection under the skin (subcutaneously).37895 In the phase 3 TRIUMPH program, weekly retatrutide was tested against placebo alongside a healthy diet and physical activity.9

Study Participants Length Doses tested
Phase 1b (2022) 72 adults with type 2 diabetes 12 weeks 0.5 mg, 1.5 mg or 3 mg; or stepped up to 6 mg (3, then 6) or to 12 mg (3, 6, 9, then 12). Placebo and dulaglutide 1.5 mg were comparators3
Phase 2 obesity trial (2023) 338 adults with obesity or overweight 48 weeks 1 mg; 4 mg or 8 mg, each started at 2 mg or 4 mg; 12 mg started at 2 mg7
Phase 2 diabetes trial (2023) 281 adults with type 2 diabetes 36 weeks 0.5 mg; 4 mg started at 2 mg or with no step-up; 8 mg started at 2 mg or 4 mg; 12 mg started at 2 mg8
TRIUMPH-1 and TRIUMPH-2, phase 3 2,339 adults without diabetes; 1,152 adults with type 2 diabetes 80 weeks 4 mg, 9 mg or 12 mg46
TRANSCEND-T2D-1, phase 3 537 adults with type 2 diabetes 40 weeks 4 mg, 9 mg or 12 mg5
TRIUMPH-3 and TRIUMPH-4, phase 3 (company toplines) 1,949 adults with severe obesity and established cardiovascular disease; 445 adults with knee osteoarthritis and obesity or overweight 80 and 68 weeks 9 mg or 12 mg1011

The trial registry adds detail on the phase 2 obesity trial's 12 mg arm.12 It started at 2 mg, then moved to 4 mg, 8 mg and finally 12 mg.12 The registry does not state how long each step lasted.12

What the starting dose changed

In the phase 2 obesity trial, gastrointestinal side effects were dose-related and mostly mild to moderate.7 They were partly reduced by starting at 2 mg instead of 4 mg.7 In the registry's posted results for the two 8 mg groups, nausea affected 6 of 35 people who started at 2 mg and 21 of 35 who started at 4 mg.12 The full pattern of side effects by trial is on Retatrutide side effects.

Dose and response

In the 48-week phase 2 obesity trial, weight loss grew with dose.7 Average weight fell 8.7% on 1 mg, 17.1% on 4 mg, 22.8% on 8 mg and 24.2% on 12 mg, versus 2.1% on placebo.7 On 12 mg, 100%, 93% and 83% of participants lost at least 5%, 10% and 15% of body weight.7 On placebo, those shares were 27%, 9% and 2%.7

In the 12-week phase 1b trial, placebo-adjusted weight loss reached 8.96 kg in the group stepped up to 12 mg.3

The 36-week phase 2 diabetes trial also compared escalation paths.8 HbA1c fell more with 8 mg (slow escalation) and 12 mg than with dulaglutide 1.5 mg.8 At 24 weeks, HbA1c fell 2.02 percentage points on 12 mg, versus 1.41 on dulaglutide and 0.01 on placebo.8 At 36 weeks, weight fell 16.94% on 12 mg, versus 2.02% on dulaglutide and 3.00% on placebo.8 Phase 3 results by dose are summarized on What is Retatrutide?.

Why study doses are not a guide

  • A different product: the trial evidence comes from drug made by Lilly. It does not describe products sold outside trials.41
  • Uncertain vial content: three vials labeled 10 mg and sold in Australia held 5.13 mg, 16.5 mg and 19.0 mg in a 2026 test.13 The amount on a label may not match the amount in the vial.13
  • Narrow populations: published phase 3 trials enrolled adults aged 18 or older.65 Retatrutide has no established role in type 1 diabetes.14
  • Limited follow-up: the longest published trials ran 80 weeks.46
  • Regulator warning: FDA says unapproved retatrutide falsely labeled for research has been sold to consumers with dosing instructions, and it urges consumers not to purchase these products, which are of unknown quality and may be harmful.2

More on Retatrutide

  • Retatrutide side effects

    Side effects of Retatrutide as reported in clinical trials, case reports and health alerts, with links to the full profile.

Frequently asked questions

What doses of retatrutide were used in clinical trials?

Phase 3 trials gave 4 mg, 9 mg or 12 mg once a week by injection under the skin, for 40 to 80 weeks.45 Two other phase 3 trials, TRIUMPH-3 and TRIUMPH-4, tested only 9 mg and 12 mg.1011 In the phase 2 obesity trial, the 12 mg group started at 2 mg and stepped up through 4 mg and 8 mg.12 All were study doses given to enrolled adults, and none is approved.1

Is there a safe retatrutide dose?

No dose has been established as safe for any person.12 FDA states that retatrutide has not been found safe and effective for any condition.2 Lilly describes it as an investigational molecule that cannot legally be sold or marketed for human use.1 Its heart and kidney outcomes trial, with about 10,000 adults, is not expected to finish until about February 2029.15

Do trials in type 2 diabetes use different retatrutide doses?

Not in phase 3. TRIUMPH-2 (1,152 adults with type 2 diabetes, 80 weeks) and TRANSCEND-T2D-1 (537 adults, 40 weeks) used the same 4 mg, 9 mg and 12 mg.65 Average weight loss was smaller in TRIUMPH-2, whose participants had diabetes: 18.8% on 12 mg, versus 25.0% in TRIUMPH-1, whose participants did not.64 Retatrutide has no established role in type 1 diabetes.14

How long does retatrutide stay in the body?

In a phase 1b trial of 72 adults with type 2 diabetes, its half-life was about 6 days.3 Blood levels rose in proportion to dose.3 The authors said its pharmacokinetics suggest it suits once-weekly dosing.3 A 2026 anti-doping study followed 4 people who had 2 mg on days 1 and 7.16 A lab method found it in blood plasma for about 56 days after the first dose, but not in urine.16

Written by D2C Peptides Editorial Team.

Pending qualified review.

Updated .

Sources

  1. Is retatrutide available in the consumer market? (Lilly Medical answer, last reviewed August 4, 2026). Eli Lilly and Company (Lilly Medical), 2026.
  2. FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss. U.S. Food and Drug Administration, 2026.
  3. LY3437943, a novel triple GIP, GLP-1, and glucagon receptor agonist in people with type 2 diabetes: a phase 1b, multicentre, double-blind, placebo-controlled, randomised, multiple-ascending dose trial. The Lancet (PubMed record, National Library of Medicine), 2022.
  4. Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity (TRIUMPH-1). New England Journal of Medicine (PubMed record, National Library of Medicine), 2026.
  5. Efficacy and safety of retatrutide, a GIP, GLP-1, and glucagon receptor agonist, in people with type 2 diabetes and inadequate glycaemic control with diet and exercise (TRANSCEND-T2D-1): a double-blind, randomised, phase 3 trial. The Lancet (PubMed record, National Library of Medicine), 2026.
  6. Retatrutide in adults with obesity and type 2 diabetes (TRIUMPH-2): a double-blind, parallel-group, randomised, placebo-controlled, phase 3 trial. The Lancet (PubMed record, National Library of Medicine), 2026.
  7. Triple-Hormone-Receptor Agonist Retatrutide for Obesity: A Phase 2 Trial. New England Journal of Medicine (PubMed record, National Library of Medicine), 2023.
  8. Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial conducted in the USA. The Lancet (PubMed record, National Library of Medicine), 2023.
  9. Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: Rationale and design of the TRIUMPH registrational clinical trials. Diabetes, Obesity and Metabolism (PubMed record, National Library of Medicine), 2026.
  10. What are the results of retatrutide from TRIUMPH-3 in adults with severe obesity and established cardiovascular disease? (Lilly Medical answer, last reviewed July 23, 2026). Eli Lilly and Company (Lilly Medical), 2026.
  11. Lilly's triple agonist, retatrutide, delivered weight loss of up to an average of 71.2 lbs along with substantial relief from osteoarthritis pain in first successful Phase 3 trial (press release, December 11, 2025; PR Newswire copy on Finviz). Eli Lilly and Company via PR Newswire, 2025.
  12. ClinicalTrials.gov NCT04881760: A Study of LY3437943 in Participants Who Have Obesity or Are Overweight (posted results: adverse events). ClinicalTrials.gov, National Library of Medicine, 2023.
  13. Composition and Labelling Accuracy of Products Sold as Retatrutide in Australia. Drug and Alcohol Review (PubMed Central full text), 2026.
  14. Online-Sourced Retatrutide Complicating Impending Diabetic Ketoacidosis in a Patient With Type 1 Diabetes and Concurrent Shigella Gastroenteritis. Cureus (PubMed record, National Library of Medicine), 2026.
  15. ClinicalTrials.gov NCT06383390 (TRIUMPH-Outcomes). ClinicalTrials.gov, National Library of Medicine, 2026.
  16. Detection and Excretion Profile of Retatrutide in Human Plasma and Urine by LC-HRMS: Implications for Antidoping Analysis. Rapid Communications in Mass Spectrometry (PubMed record, National Library of Medicine), 2026.