Retatrutide dosage and evidence

What is Retatrutide?

How does Retatrutide work?

It switches on three receptors: GLP-1, GIP and glucagon. The glucagon part makes the body burn more energy and burn more fat in the liver. The other two turn down hunger and help the body release insulin.

What have studies in people found about Retatrutide?

As of September 2026, almost everything published on retatrutide comes from mid-stage trials. There is an obesity trial in 338 people, a type 2 diabetes trial in 281, a liver fat study and a body make-up study. One large final-stage trial has been published in full: 537 people with type 2 diabetes over 40 weeks. The big final-stage obesity trials have finished, but their results have not appeared in medical journals.

• The one full final-stage report: 537 adults with type 2 diabetes not controlled by diet and exercise were treated for 40 weeks. Three-month average blood sugar fell 1.69 points on 4 mg, 1.86 on 9 mg and 1.94 on 12 mg, against 0.81 on a dummy shot. Weight fell 11.5%, 13.9% and 15.3%, against 2.6%. Between 2% and 5% quit over side effects, against none on the dummy. Two people died, both on 4 mg, and the deaths were judged unrelated.
• Obesity: 338 adults lost 24.2% of body weight on 12 mg, 22.8% on 8 mg and 17.1% on 4 mg over 48 weeks. On the dummy shot they lost 2.1%.
• Type 2 diabetes: 281 people took part and 275 were counted. At 24 weeks, three-month average blood sugar fell 2.02 points on 12 mg. It barely moved on the dummy shot and fell 1.41 on dulaglutide 1.5 mg, an older drug. At 36 weeks weight had fallen 16.94% on 12 mg, against 3.00% on the dummy and 2.02% on dulaglutide. Nobody had a severe blood sugar low and nobody died.
• Body scans from that diabetes trial: 189 people joined, but only 103 had usable scans at both the start and week 36. Fat mass fell 26.1% on 8 mg and 23.2% on 12 mg, against 4.5% on the dummy and 2.6% on dulaglutide. The authors say the share of lean tissue lost, such as muscle, was about the same as with other obesity drugs.
• Fatty liver side study: at 24 weeks, liver fat fell to normal (under 5%) in 86% on 12 mg, 79% on 8 mg and 52% on 4 mg. Nobody on the dummy shot got there.
• The main obesity trial (NCT05929066) is listed as finished with 2,335 people. No journal report existed when we checked. The 80-week weight figure quoted widely online comes from a company press release, not a paper.
• Three more finished trials have published nothing: 1,152 people with type 2 diabetes and obesity (NCT05929079), 1,946 people with severe obesity who already have heart disease (NCT05882045), and 445 people with knee arthritis (NCT05931367).
• A head-to-head against tirzepatide in 800 adults with obesity (NCT06662383) is still running. It is no longer taking new people and is due to finish in December 2026.
• The only trial that will count heart attacks, strokes, kidney failure and deaths (NCT06383390) has 10,000 people with a body mass index of 27 or more and heart or kidney disease. Its main results are due in February 2029.

What this does not tell you: Almost everything known about retatrutide in people comes from trials of a few hundred people lasting under a year. There is no published paper from the large obesity trials. There is no heart or kidney outcome data of any kind before 2029, and no head-to-head result against tirzepatide yet. In the mid-stage trials, heart rate went up as the dose went up. Nobody has followed that to see what it leads to. The body scan data come from 103 people with usable scans, which is a thin basis for feeling sure about muscle. Nothing is known about use past 80 weeks, in teenagers, or in pregnancy. Most important if you are thinking of buying it: retatrutide is not approved anywhere. Every number here came from Eli Lilly's own drug, given under trial supervision. No published study has tested what is actually in a vial sold as 'research-grade' retatrutide.

What do people who took Retatrutide report?

This is what real people say happened to them, good and bad. Nobody measured it. A report cannot tell a real effect from the lift people get just from expecting it to work, from a diet or training change made at the same time, or from what was really in the vial. We still put it near the top. It is the next best thing to a study in people: what happens when real people use it, including what goes wrong.

• The dose people describe starting on for weight loss clusters around 2 mg weekly, and the most repeated piece of advice is that people who are already lean and using it to cut find that starting dose considerably stronger than people using it for obesity do. Starting lower is the standard suggestion in that second group.
• Results are described as spread rather than average. Several long-running posters make the same point independently: the mean figure from the trials is not what most individuals get, and being well above or well below it is more common than landing near it.
• A distinctive and frequently discussed effect is mild ketosis appearing even when people are eating plenty of carbohydrate, The more technical posters put this down to the drug's glucagon side, which makes the liver produce its own sugar. The same posters argue this is not automatically muscle sparing, and warn bodybuilders that the glucagon component may work against them.
• Persistent fatigue is the negative raised most often, described by some as continuing for months and as distinct from what the same people experienced on semaglutide or tirzepatide. Nausea and the usual stomach and gut complaints appear as well, and a recurring counter-theme is other users telling someone their reported fatigue is not real, which those posters push back on.
• Pairing with cagrilintide is commonly described by people who want their appetite cut more than retatrutide alone does it. Pairing with peptides that make the body release growth hormone appears in stacks aimed at body shape.
• Because there is no approved product, everything discussed is grey market, and sourcing dominates. People describe vendors mislabelling batches, including a case where two products were sent out wearing each other's labels, and third party testing is treated as necessary rather than optional. Disagreement about whether a failed cycle means the compound did nothing or the vial was not what it claimed is constant.
• A common framing among longer-term users is that this is chronic therapy rather than a course, with weight returning after stopping, and that framing is itself contested in the same threads.

Sources: Public discussion in r/Retatrutide, r/PEDs, r/zepbound_support and adjacent weight loss subreddits, read through the PullPush Reddit archive on 2026-09-13 because Reddit's own endpoints are unreachable from this environment. 86 comments reviewed. Nothing above is attributed to any specific post and no comment is reproduced.

The state of the research

The evidence, in charts

The studies we cite

• Study in people2023
  Triple-Hormone-Receptor Agonist Retatrutide for Obesity: A Phase 2 Trial

  It worked, and this is still an early trial. 338 adults with obesity took retatrutide or a dummy injection every week for about eleven months. The dummy group finished about 2% lighter. On the strongest dose people finished about 24% lighter, with smaller losses on smaller doses. This was a middle stage trial, built to find the right dose rather than to prove long term benefit or safety. No full size trial of this drug has been published yet.

  338 adults over 48 weeks (NCT04881760): least-squares mean body weight change of -24.2% at 12 mg, -22.8% at 8 mg and -17.1% at 4 mg versus -2.1% with placebo.

  PMID 37366315 New England Journal of Medicine
• Study in people2024
  Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial

  Retatrutide cleared fat out of the liver in a small side study. People with obesity and a fatty liver took the drug or a dummy injection for six months, inside the larger trial. By the end, liver fat had come back into the normal range for 86% of those on the strongest dose, 79% on the middle dose and 52% on the lowest. Nobody on the dummy injection got there. This measured fat on a scan, not whether anyone lived longer or felt better.

  Phase 2a substudy (NCT04881760): at 24 weeks, normal liver fat (below 5%) was reached by 86% of participants on 12 mg, 79% on 8 mg and 52% on 4 mg versus 0% on placebo.

  PMID 38858523 Nature Medicine
• Study in people2026
  A Master Protocol to Investigate the Efficacy and Safety of LY3437943 Once Weekly in Participants Without Type 2 Diabetes Who Have Obesity or Overweight (TRIUMPH-1)

  The company says this worked, and the paper has not appeared yet. More than 2,300 adults were signed up to a full size retatrutide trial that has now finished. In a press release in May 2026 the maker reported that people on the 12 mg dose finished about 28% lighter after eighty weeks, against about 2% on the dummy injection. Nobody outside the company has checked those figures. Treat them as a claim until the paper is published.

  Registry record for the completed Phase 3 TRIUMPH-1 trial (2,335 enrolled per the registry). Lilly's May 21, 2026 topline release reported -28.3% at 80 weeks on 12 mg versus -2.2% on placebo; the peer-reviewed paper was not yet indexed at review time.

  NCT05929066 ClinicalTrials.gov NCT05929066
• Study in people2023
  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

  Retatrutide lowered blood sugar and weight more than an older drug, in a mid-stage trial. 281 people with type 2 diabetes were split by chance between retatrutide, dulaglutide and a dummy shot, and nobody involved knew which. At the top dose, average blood sugar over three months fell about 2 points, against almost nothing on the dummy and 1.41 on dulaglutide. Weight fell 16.94% against 3.00%. Nobody had a severe sugar low and nobody died. It ran under a year.

  281 randomized, 275 analysed (NCT04867785): HbA1c -2.02% at 12 mg versus -0.01% on placebo and -1.41% on dulaglutide at 24 weeks; body weight -16.94% versus -3.00% and -2.02% at 36 weeks. No severe hypoglycaemia and no deaths.

  PMID 37385280 The Lancet
• Study in people2026
  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

  This is the first full late-stage report for retatrutide, and it holds up. 537 people with type 2 diabetes not controlled by diet and exercise took the drug or a dummy shot for 40 weeks. Nobody involved knew which. Average blood sugar over three months fell between 1.69 and 1.94 points across the doses, against 0.81 on the dummy. Weight fell between 11.5% and 15.3%, against 2.6%. This is a diabetes trial, not the obesity trials everyone is waiting for.

  537 participants over 40 weeks (NCT06354660): HbA1c -1.69% to -1.94% across doses versus -0.81% on placebo, and body weight -11.5% to -15.3% versus -2.6%. The first fully published Phase 3 result for retatrutide.

  PMID 42250575 The Lancet
• Study in people2025
  Effects of retatrutide on body composition in people with type 2 diabetes: a substudy of a phase 2, double-blind, parallel-group, placebo-controlled, randomised trial

  Most of the weight lost was fat, on scans from a small slice of a larger trial. 189 people joined the scan study and only 103 had usable scans at both the start and week 36. Fat mass fell 26.1% and 23.2% at the two higher doses, against 4.5% on the dummy shot. The share of the loss that was muscle looked like what other obesity drugs produce. 103 people is a thin basis for reassurance about muscle.

  189 enrolled in the DXA substudy, 103 with both baseline and week 36 scans: total fat mass fell 26.1% on pooled 8 mg and 23.2% on 12 mg versus 4.5% on placebo. The lean mass proportion of total loss was similar to other obesity treatments.

  PMID 40609566 The Lancet Diabetes & Endocrinology
• Study in people2026
  A Master Protocol to Investigate the Efficacy and Safety of LY3437943 Once Weekly in Participants With Type 2 Diabetes Mellitus Who Have Obesity or Overweight: A Randomized Double-Blind, Placebo-Controlled Trial

  This trial finished and has published nothing. It tested retatrutide in 1,152 people with obesity and type 2 diabetes, and the registry lists it as completed in June 2026. No results have been posted there and no paper has appeared. A completed trial that reports nothing is itself a finding. It is why no dependable late-stage figure for this drug can be quoted yet.

  Registry record for the Phase 3 obesity and type 2 diabetes trial: 1,152 participants, listed as completed with primary completion June 16, 2026. No results posted and no peer-reviewed publication indexed at review.

  NCT05929079 ClinicalTrials.gov NCT05929079 (TRIUMPH-2), Eli Lilly
• Study in people2026
  A Randomized, Double-Blind, Phase 3 Study to Investigate the Efficacy and Safety of LY3437943 Once Weekly Compared to Placebo in Participants With Severe Obesity and Established Cardiovascular Disease

  This trial finished and has published nothing either. 1,946 people with severe obesity who already had heart disease took part, and the registry says it completed in May 2026. No results have been posted. Note what it was built to measure, which is weight, in people who happen to have heart disease. It was never designed to show whether retatrutide prevents heart attacks or strokes.

  Registry record: 1,946 participants with severe obesity and established cardiovascular disease, listed as completed in May 2026 with no results posted. This is a weight trial in a cardiovascular population, not a cardiovascular outcome trial.

  NCT05882045 ClinicalTrials.gov NCT05882045 (TRIUMPH-3), Eli Lilly
• Study in people2025
  A Phase 3 Study to Investigate the Efficacy and Safety of LY3437943 Once Weekly in Participants Who Have Obesity or Overweight and Osteoarthritis of the Knee: A Randomized, Double-Blind, Placebo-Controlled Trial

  A third completed retatrutide trial with nothing published. 445 people with obesity or extra weight and knee arthritis took part, and the registry lists it as completed on 14 November 2025. No results have been posted and no paper was indexed when we checked. Whether the drug helps a painful knee is therefore still unknown, and a finished trial that reports nothing is itself a finding.

  Registry record: 445 participants with obesity or overweight and knee osteoarthritis, listed as completed November 14, 2025, with no results posted at review.

  NCT05931367 ClinicalTrials.gov NCT05931367 (TRIUMPH-4), Eli Lilly
• Study in people2026
  A Phase 3, Randomized, Double-Blind Study to Evaluate the Efficacy and Safety of Retatrutide Compared to Tirzepatide in Adults Who Have Obesity

  Nobody has yet compared retatrutide against tirzepatide, so anyone who tells you which is stronger is guessing. The trial that will answer it has enrolled 800 adults with obesity and is still running, with completion listed for December 2026. It is no longer taking new people. Until it reports, every ranking of these two drugs comes from holding separate trials side by side, which is not the same thing.

  The head-to-head against tirzepatide: 800 adults with obesity, listed as active and not recruiting with completion in December 2026. No result exists yet, so any current claim that retatrutide beats tirzepatide rests on cross-trial comparison.

  NCT06662383 ClinicalTrials.gov NCT06662383 (TRIUMPH-5), Eli Lilly
• Study in people2026
  A Phase 3, Randomized, Double-Blind, Placebo-Controlled, Event-Driven Study to Investigate the Effect of Retatrutide on the Incidence of Major Adverse Cardiovascular Events and Major Adverse Kidney Events in Participants With Body Mass Index ≥27 kg/m2 and Atherosclerotic Cardiovascular Disease and/or Chronic Kidney Disease

  Nothing is known about what retatrutide does to heart attacks, strokes or kidney failure. This is the only trial built to find out, and it is still running. 10,000 people with extra weight and either heart or kidney disease are enrolled, and the first results are not due until February 2029. Everything published so far measures weight and blood sugar, which are not the events people take these drugs to avoid.

  The only retatrutide trial with hard clinical endpoints: 10,000 participants, event-driven, primary completion listed for February 2029. Until it reports, nothing is known about retatrutide and cardiovascular or kidney outcomes.

  NCT06383390 ClinicalTrials.gov NCT06383390 (TRIUMPH-Outcomes), Eli Lilly
• Review of studies2026
  Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: rationale and design of the TRIUMPH registrational clinical trials

  This paper lays out the plan for the four big retatrutide studies, with more than 5,800 people in all. They cover weight, sleep apnea and knee arthritis. TRIUMPH-4 is the one just for knee arthritis. It is a plan, not a result.

  Describes the four Phase 3 TRIUMPH trials (over 5,800 participants) with weight-management, sleep apnea and knee osteoarthritis baskets; TRIUMPH-4 is the stand-alone osteoarthritis trial.

  PMID 41090431 Diabetes, Obesity & Metabolism