Peptides Vietnam LogoPeptides Vietnam
MetabolicTrial DosesSep 2026

Retatrutide Dosage: What the Phase 2 and 3 Trials Used

Retatrutide is the triple hormone receptor agonist that keeps turning up in weight loss headlines, and the first thing people search for is the dose. This page answers a narrower, more honest question: what doses did the actual trials use. The phase 2 programme ran maintenance doses from 0.5 mg to 12 mg once weekly across two trials (trial doses, not a recommendation, PMID 37366315 and PMID 37385280), the two phase 3 trials that have published their numbers used 4, 9, and 12 mg in type 2 diabetes and 9 and 12 mg in knee osteoarthritis (trial doses, not a recommendation, PMID 42250575 and Lilly Medical Information), and the large phase 3 obesity programme has not disclosed its milligram values at all. Every figure below is a trial arm given under medical supervision. None of it is a recommendation, and this page does not tell anyone what to take.

This is general education, not medical advice, and not a dose to copy. Retatrutide is an investigational drug. The US Food and Drug Administration says it is not a component of any approved drug and has not been found safe and effective for any condition, and that it cannot legally be used in compounding.12 Every milligram figure on this page is a clinical trial arm, assigned and monitored by investigators. Nothing here is a starting dose, an escalation schedule to follow, a protocol, or a source. If you are weighing any of this, the decision belongs with a licensed clinician, not a webpage.

3-in-1

GIP, GLP-1 and glucagon agonist

Once weekly

Subcutaneous in every human trial

Investigational

Not approved by the FDA

What Retatrutide Is

Retatrutide, known in the research literature by its development code LY3437943, is a single peptide that acts on three receptors at once: the receptors for GIP, GLP-1, and glucagon.4 The trial papers describe it as a novel synthetic molecule and a triple hormone receptor agonist.7 In the lab it shows balanced activity at the glucagon and GLP-1 receptors and more activity at the GIP receptor.4 That triple action is why it is being studied for obesity and type 2 diabetes, and why the dose question is more interesting than it looks: the trials had to find a level that balanced effect against the side effects that come with hitting three pathways.

Two facts frame everything on this page. First, in every human study in this review the drug was given the same way, a subcutaneous injection, once weekly, which its reported half-life of about 6 days supports (phase 1b trial, PMID 36354040).13 Second, it is investigational. The FDA says retatrutide is not a component of any approved drug and has not been found safe and effective for any condition,12 and the manufacturer itself calls it an investigational agent under clinical development.116 There is no approved label, so there is no approved dose. What exists is a set of trial arm assignments, and that is what follows.

The Phase 2 Doses

The dose ladder started in a phase 1b study in people with type 2 diabetes. Over 12 weeks it ran once-weekly cohorts of 0.5 mg, 1.5 mg, and 3 mg, plus two escalation cohorts that stepped up to 6 mg and, in the top cohort, up to 12 mg (trial doses, not a recommendation, PMID 36354040).3 That study reported the roughly 6 day half-life behind weekly dosing and a placebo-adjusted weight reduction of up to 8.96 kg in the top escalation cohort (phase 1b trial, PMID 36354040). Those results set up the phase 2 programme.

Read the table as history, not instruction. Every figure below is a dose a clinical trial assigned and monitored. None of it is a recommendation or a starting point, and the milligram values are reported exactly as the trials and their registry records stated them.

Trial (phase and population)Once-weekly doses studiedSource
Phase 1b, type 2 diabetes (NCT04143802)0.5, 1.5 and 3 mg fixed cohorts, plus escalation cohorts stepping up to 6 mg and to 12 mgPMID 36354040
Phase 2, obesity (NCT04881760)1, 4, 8 and 12 mg maintenance, once weeklyPMID 37366315
Phase 2, type 2 diabetes (NCT04867785)0.5, 4, 8 and 12 mg maintenance, once weeklyPMID 37385280
Phase 2a, liver fat substudy (NCT04881760)1, 4, 8 and 12 mg, once weeklyPMID 38858523
Phase 2b, chronic kidney disease (NCT05936151)No fixed dose. Maximum tolerated dose, up to 12 mgPMID 41160422
Phase 3, type 2 diabetes (TRANSCEND-T2D-1, NCT06354660)4, 9 and 12 mg, once weeklyPMID 42250575
Phase 3, knee osteoarthritis with obesity or overweight (TRIUMPH-4, NCT05931367)9 and 12 mg targets, started at 2 mg and titrated at 4-week intervalsLilly Medical Information
Phase 3, obesity programme (TRIUMPH-1, 2, 3 and related trials)Not disclosed. Registry lists arms only as Dose 1, Dose 2, Dose 3ClinicalTrials.gov
Phase 3, cardiovascular and kidney outcomes (TRIUMPH-Outcomes, NCT06383390)No fixed dose. Escalated to a maximum tolerated doseClinicalTrials.gov

The phase 2 obesity trial is the one most people mean when they talk about retatrutide. It enrolled 338 adults with obesity and ran for 48 weeks, testing once-weekly maintenance doses of 1 mg, 4 mg, 8 mg, and 12 mg (trial doses, not a recommendation, PMID 37366315).1 Several arms reached 4 mg and 8 mg from two different starting doses, a 2 mg start and a 4 mg start, which is why the published arm list looks more complicated than four numbers. At 48 weeks the trial reported average weight reductions of about 8.7% at 1 mg, 17.1% at the combined 4 mg arms, 22.8% at the combined 8 mg arms, and 24.2% at 12 mg, against 2.1% on placebo (phase 2 trial, 48 weeks, PMID 37366315). The response climbed with the dose, which is exactly why the higher doses carried into phase 3.

The phase 2 type 2 diabetes trial ran in parallel. It randomised 281 adults across 42 US centres and tested once-weekly retatrutide at 0.5 mg, 4 mg, 8 mg, and 12 mg, alongside placebo and a dulaglutide comparator (trial doses, not a recommendation, PMID 37385280).2 Its main measure was blood sugar: at 24 weeks HbA1c fell by up to 2.02% at 12 mg versus almost no change on placebo, and body weight fell by up to about 16.9% at 12 mg by 36 weeks (phase 2 trial, PMID 37385280). The authors say plainly that this trial informed the dose selection for the phase 3 programme, which is the thread that leads to the 4, 9, and 12 mg you see later.

A substudy of the obesity trial looked at liver fat at the same 1, 4, 8, and 12 mg doses, and the dose-response was steep: relative liver fat reductions of about 42.9% at 1 mg rising to 82.4% at 12 mg by 24 weeks (phase 2a substudy, PMID 38858523).5 Across all of these arms, the two different starting doses were not a menu, they were a measurement. The trial found that the lower 2 mg start partially reduced the gastrointestinal side effects, which is a finding about tolerability, not a protocol.1

The Phase 3 Doses

Here the story splits. Two phase 3 retatrutide trials in this review have published their milligram doses, and both are in a complication population rather than the flagship obesity readout. TRANSCEND-T2D-1, a 40-week type 2 diabetes trial run across 48 sites in the USA, Mexico, and India, randomised 537 adults to once-weekly retatrutide at 4 mg, 9 mg, or 12 mg, or placebo (trial doses, not a recommendation, PMID 42250575).6 At 40 weeks it reported HbA1c falling further at higher doses and average weight reductions of about 11.5% at 4 mg, 13.9% at 9 mg, and 15.3% at 12 mg, against 2.6% on placebo (phase 3 trial, 40 weeks, PMID 42250575).

The other is TRIUMPH-4, a phase 3, 68-week stand-alone trial in adults who have obesity or overweight and osteoarthritis of the knee. Its doses are not in a journal paper but in preliminary results the manufacturer posted to its medical information site: its 445 participants were randomised 1:1:1 to retatrutide escalated to a 9 mg or 12 mg maximum, or placebo, each started at 2 mg and titrated at 4-week intervals (trial doses, not a recommendation, Lilly Medical Information).1510 Those preliminary results reported average weight reductions of about 26.4% at 9 mg and 28.7% at 12 mg, against 2.1% on placebo (phase 3 trial, 68 weeks, Lilly Medical Information).

The 9 mg dose is worth pausing on, because it is new. It does not appear as a maintenance dose in any phase 2 retatrutide arm. The only earlier place a 9 is visible at all is as a transit step inside the phase 1b escalation ladder that stepped up to 12 mg.3 So 9 mg is a phase 3 dose level, chosen for these trials, not something carried over from the phase 2 work. That is a small detail with a large lesson: the doses that reach late-stage trials are engineered choices, not round numbers a reader can back into.

The Doses Nobody Published

The obesity side of phase 3 is where the honest answer gets uncomfortable. The registrational obesity programme, called TRIUMPH, is four phase 3 trials in over 5,800 participants, all using weekly subcutaneous retatrutide against placebo.7 The design paper states the route and the schedule and no milligram figure for any arm. The ClinicalTrials.gov records do the same: the arms are labelled only Retatrutide Dose 1, Dose 2, and Dose 3, and the intervention is described only as administered subcutaneously.10

That registry masking is consistent across the whole registered phase 3 programme, TRIUMPH-4 included. What is public did not come from the registry: as of this review no peer-reviewed TRIUMPH results paper has been published, and the only phase 3 milligram doses in the public record are the 4, 9, and 12 mg from the TRANSCEND-T2D-1 diabetes trial and the 9 and 12 mg from TRIUMPH-4, whose preliminary results the manufacturer posted to its medical information site.615 Some phase 3 trials go further and use no fixed dose at all: the 10,000 participant cardiovascular and kidney outcomes trial escalates each participant to a maximum tolerated dose,10 and the phase 2b kidney study did the same, up to 12 mg.8

This is the part a dosage page has to be straight about. For phase 3 obesity, the specific doses are simply not public yet. A number filled in here would be a guess dressed as a fact, and that is the one thing this page will not do.

What the Trials Reported

Dose and side effects are linked here, which is the whole reason the trials escalated so carefully. Across the studies the most common adverse events were gastrointestinal, mostly mild to moderate, and they tracked with the dose.1 In the phase 2 type 2 diabetes trial, gastrointestinal events ranged from about 13% of participants in the lowest 0.5 mg group to about 50% in one of the fast-escalation 8 mg groups, with no severe hypoglycaemia and no deaths reported (phase 2 trial, PMID 37385280).2 The obesity trial also reported dose-dependent increases in heart rate that peaked at 24 weeks and then declined (phase 2 trial, PMID 37366315).

The phase 3 type 2 diabetes trial reported the same general pattern: mostly mild to moderate gastrointestinal events that subsided over time, discontinuations for adverse events of roughly 2 to 5% on retatrutide versus none on placebo, no severe hypoglycaemia, and two deaths, both in the 4 mg group and both judged unrelated to the study drug (phase 3 trial, PMID 42250575).6 None of this is a safety verdict for use outside a trial. It is what investigators observed under monitoring at fixed, assigned doses.

Why This Is Not a Dose to Copy

Everything above is a trial arm, and a trial arm is not a prescription. Retatrutide has no approved label anywhere in this review, so there is no sanctioned dose, no titration schedule, and no approved indication to frame one.12 The FDA has been explicit: retatrutide cannot be used in compounding under federal law, and it has warned companies selling it under research use only or not for human consumption labelling, and telehealth companies marketing it directly to consumers.12 There is a named, dated enforcement record to match, a March 2026 FDA warning letter to a peptide seller offering retatrutide as an unapproved new drug.13

One product record can look like an exception to that, and it is worth naming so it is not mistaken for one. DailyMed, the drug label repository run by the US National Library of Medicine, carries a set of Structured Product Labeling records for a retatrutide product branded SALKALLI, with pen strengths listed as high as 40 mg and a titration of 2.5 mg, 5 mg, 7.5 mg, then 10 mg once weekly.16 That is not an FDA approval. Every one of those records was filed by a single labeler, Guangzhou Yixin Cross-border E-commerce Co., Ltd., and every one is marked as export only, which is a filing the registrant itself submits, not a review or an authorisation by the FDA.16 The tell is in the numbers: that 2.5, 5, 7.5 and 10 mg ladder, and the pen strengths up to 40 mg, match no retatrutide trial fetched for this page, whose arms ran from 0.5 mg to 12 mg with a 2 mg or 4 mg start. A schedule that turns up on the export filing of a cross-border seller and in none of the trials is not a schedule to copy.

Why does the exact number matter so much? Because with this class of drug, dosing errors have already put people in hospital. The FDA has reported adverse events, some requiring hospitalisation, from dosing errors with compounded semaglutide, a different GLP-1 drug, where patients or clinicians measured and injected the wrong amount.12 That is a semaglutide finding, not a retatrutide one, but it is the clearest illustration of why a milligram figure lifted from a trial is not something to reverse-engineer at home.

There is exactly one supervised route to retatrutide outside a clinical trial, and it is narrow: the manufacturer runs a pre-approval expanded access programme for adults with severe obesity, a body mass index of 35 or higher, and at least two serious obesity-related complications, who are refractory to approved therapy and cannot join a trial.11 It is not a shortcut to a dose. And where people reach for animal data to justify a number, the animal record does not supply one either: the discovery paper reports that retatrutide reduced body weight in obese mice but states no dose (mouse study, PMID 35985340),4 and the one isolated-tissue study used a fixed concentration of 100 nM in a mouse atrial preparation, not an injected dose in a living animal (animal study, isolated mouse atria, not an in vivo route, PMID 40464942).9

On availability closer to home, this review could not confirm a Vietnamese pharmacy listing, a price, or a registration number with the Drug Administration of Vietnam, but most of those checks were blocked or inconclusive rather than clean negatives, so nothing here should be read as saying retatrutide is unavailable or unregistered in Vietnam.14 The right move is to confirm the current status directly with the Drug Administration of Vietnam. For the neighbouring GLP-1 drug that is further along the approval path, the semaglutide in Vietnam guide covers the same regulatory ground in more depth.

The Short Version

  • Retatrutide (LY3437943) is an investigational once-weekly injection acting on the GIP, GLP-1, and glucagon receptors; it has no approved label and no approved dose.
  • Phase 2 tested once-weekly maintenance doses from 0.5 mg to 12 mg: an obesity trial at 1, 4, 8, and 12 mg, and a type 2 diabetes trial at 0.5, 4, 8, and 12 mg.
  • Several phase 2 arms reached the same dose from a 2 mg or a 4 mg start, to measure tolerability, not to prescribe an escalation.
  • Two phase 3 trials have published their doses: 4, 9, and 12 mg once weekly in type 2 diabetes, and 9 and 12 mg in a knee osteoarthritis trial; 9 mg is a new phase 3 level, not a phase 2 dose.
  • The large phase 3 obesity programme (the weight-management TRIUMPH trials) has not disclosed its milligram doses; the arms are labelled only Dose 1, 2, and 3.
  • 12 mg once weekly is the highest maintenance dose in any published trial here; some trials instead escalate to a maximum tolerated dose.
  • Every figure here is a monitored trial arm, not a recommendation; retatrutide dosing is a clinician and trial matter, not a solo experiment.

Frequently asked questions

What doses of retatrutide did the phase 2 trials use?+

Two phase 2 trials carried the main range. The obesity trial tested maintenance doses of 1 mg, 4 mg, 8 mg, and 12 mg once weekly, and the type 2 diabetes trial tested 0.5 mg, 4 mg, 8 mg, and 12 mg once weekly, all by subcutaneous injection (trial doses, not a recommendation, PMID 37366315 and PMID 37385280). Several arms reached the same maintenance dose from different starting doses, because the trials were measuring tolerability, not writing a protocol for anyone to copy.

What doses did the phase 3 trials use?+

Two phase 3 trials have published their milligram values so far. TRANSCEND-T2D-1, a type 2 diabetes trial, used 4 mg, 9 mg, and 12 mg once weekly (trial doses, not a recommendation, PMID 42250575), and TRIUMPH-4, a knee osteoarthritis trial in people with obesity or overweight, used 9 mg and 12 mg targets, each started at 2 mg and titrated at 4-week intervals (trial doses, not a recommendation, Lilly Medical Information). The rest of the large phase 3 obesity programme, the weight-management TRIUMPH trials and the others, has not disclosed its doses: the design paper reports no milligram figure for any arm (PMID 41090431), and the trial registry lists those arms only as Dose 1, Dose 2, and Dose 3 (ClinicalTrials.gov). So the honest answer is that most phase 3 doses are still not public.

What is the highest retatrutide dose used in a trial?+

12 mg once weekly is the highest maintenance dose stated in any published retatrutide trial in this review (trial dose, not a recommendation, PMID 37366315). Some later trials do not use a fixed dose at all, and instead escalate each participant to a maximum tolerated dose of up to 12 mg under supervision (PMID 41160422). None of that makes 12 mg a target for anyone outside a monitored trial.

Why did the trials test two different starting doses?+

In the phase 2 obesity trial, some arms reached the same maintenance dose from a 2 mg start and others from a 4 mg start, so the investigators could compare tolerability. The trial reported that the lower 2 mg start partially reduced the gastrointestinal side effects that are common with this drug class (phase 2 trial finding, PMID 37366315). That is a result about the trial design, not an escalation schedule for a reader to follow.

Is retatrutide an approved medicine you can be prescribed a dose of?+

No. Retatrutide is investigational. The US Food and Drug Administration states it is not a component of any approved drug, that it has not been found safe and effective for any condition, and that it cannot legally be used in compounding (FDA, 2026). The manufacturer runs a narrow pre-approval expanded access route for adults with severe obesity and serious complications who cannot join a trial, and that is the only supervised path outside the trials themselves (ClinicalTrials.gov NCT07629401). There is no approved label and no approved dose.

Is retatrutide available in Vietnam?+

This review could not confirm a Vietnamese pharmacy listing, a price, or a Drug Administration of Vietnam registration number for retatrutide, but most of those checks were blocked or returned inconclusive results, so this is not evidence that the drug is unavailable or unregistered. Anyone who needs the current regulatory status in Vietnam should confirm it directly with the Drug Administration of Vietnam rather than rely on a search that could not complete.

Sources and references

  1. 1.Triple-Hormone-Receptor Agonist Retatrutide for Obesity: A Phase 2 Trial. New England Journal of Medicine, 2023. ClinicalTrials.gov NCT04881760. PMID 37366315. PubMed PMID 37366315
  2. 2.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. The Lancet, 2023. NCT04867785. PMID 37385280. PubMed PMID 37385280
  3. 3.LY3437943, a novel triple GIP, GLP-1, and glucagon receptor agonist in people with type 2 diabetes: a phase 1b multiple-ascending dose trial. The Lancet, 2022. NCT04143802. PMID 36354040. PubMed PMID 36354040
  4. 4.LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: from discovery to clinical proof of concept. Cell Metabolism, 2022. PMID 35985340. PubMed PMID 35985340
  5. 5.Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial. Nature Medicine, 2024. NCT04881760. PMID 38858523. PubMed PMID 38858523
  6. 6.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, 2026. NCT06354660. PMID 42250575. PubMed PMID 42250575
  7. 7.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, 2026. PMID 41090431. PubMed PMID 41090431
  8. 8.Rationale, design and baseline characteristics of the TRANSCEND-CKD trial of retatrutide in patients with chronic kidney disease. Nephrology Dialysis Transplantation, 2026. NCT05936151. PMID 41160422. PubMed PMID 41160422
  9. 9.Contractile effects of retatrutide in isolated mouse atrial preparations. Naunyn Schmiedebergs Archives of Pharmacology, 2025. PMID 40464942. PubMed PMID 40464942
  10. 10.ClinicalTrials.gov, retatrutide trial registry. Phase 2 and phase 3 records, arm labels and enrolments, fetched via the public API v2, 2026. clinicaltrials.gov / retatrutide
  11. 11.Pre-approval Expanded Access of Retatrutide (LY3437943). ClinicalTrials.gov NCT07629401. Sponsor Eli Lilly and Company, status Available. clinicaltrials.gov / NCT07629401
  12. 12.US Food and Drug Administration. FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss. Content current as of 09/01/2026. fda.gov / unapproved GLP-1 drugs
  13. 13.US Food and Drug Administration. Warning Letter to Gram Peptides, reference 721806, March 31, 2026. fda.gov / warning letter 721806
  14. 14.Drug Administration of Vietnam, Ministry of Health. Public service portal for drug registration and price management. dichvucong.dav.gov.vn
  15. 15.Eli Lilly. What are the preliminary results with retatrutide from TRIUMPH-4 in participants with obesity or overweight and osteoarthritis? Lilly Medical Information (US). ClinicalTrials.gov NCT05931367. Fetched 2026-09-06. medical.lilly.com / TRIUMPH-4 preliminary results
  16. 16.DailyMed, US National Library of Medicine. Structured Product Labeling records for retatrutide (brand SALKALLI), labeler Guangzhou Yixin Cross-border E-commerce Co., Ltd., marketing category Export only, published Nov 17, 2025. Fetched 2026-09-06. dailymed.nlm.nih.gov / retatrutide SPL

Related reading

Semaglutide in Vietnam

A GLP-1 drug further along the approval path

Reconstitution Calculator

Concentration and volume for a lyophilised peptide

Bac Water vs Sterile Water

The water used to reconstitute injectables

Peptides FAQ

Common questions on sourcing, safety, and basics

This guide is for educational purposes only and is not medical advice. It describes what published clinical trials reported about the doses they used; it is not an endorsement, a recommendation, or an instruction to use any compound. Retatrutide is an investigational drug that is not approved for use. Consult a qualified healthcare professional before making any decision about your health.

Sources

  1. 1.PubMed PMID 37366315
  2. 2.PubMed PMID 37385280
  3. 3.PubMed PMID 36354040
  4. 4.PubMed PMID 35985340
  5. 5.PubMed PMID 38858523
  6. 6.PubMed PMID 42250575
  7. 7.PubMed PMID 41090431
  8. 8.PubMed PMID 41160422
  9. 9.PubMed PMID 40464942
  10. 10.clinicaltrials.gov / retatrutide
  11. 11.clinicaltrials.gov / NCT07629401
  12. 12.fda.gov / unapproved GLP-1 drugs
  13. 13.fda.gov / warning letter 721806
  14. 14.dichvucong.dav.gov.vn
  15. 15.medical.lilly.com / TRIUMPH-4 preliminary results
  16. 16.dailymed.nlm.nih.gov / retatrutide SPL