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Retatrutide guide

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PepCaddie provides educational summaries of published and registered research. It does not sell peptides, provide medical advice, or recommend the use of any investigational substance. Discuss health decisions with a qualified healthcare professional.

This retatrutide guide covers what has actually been published about the compound, which is not the same as what is quoted about it. Retatrutide is investigational: no regulator identified has approved it112. It does have real human trials behind it, and the results of those trials are worth reading carefully, because the headline number attached to retatrutide online comes from a single mid-stage study.

The short answer

  • What it is: one synthetic peptide that activates three receptors, GLP-1, GIP and glucagon. The glucagon arm is what separates it from tirzepatide, which acts on two.
  • Approved? No. Not in the United States, and no approval elsewhere was identified112.
  • Human evidence: substantial for a compound at this stage. Published phase 2 trials in obesity and type 2 diabetes, a liver-fat substudy, a phase 1 study with pharmacokinetics, and one published phase 3 diabetes trial6.
  • The gap: the two completed phase 3 obesity trials, about 3,500 participants between them, have posted no results and published nothing910.
  • Unknown: effects on the heart and kidneys over time, long-term safety, what happens after stopping, and how it compares with tirzepatide or semaglutide1113[unverified].

What the published trials found

The number you will see everywhere, a 24.2 per cent reduction in body weight, comes from the phase 2 obesity trial: 338 people, 48 weeks, highest dose, against 2.1 per cent on placebo4. That is a real result from a real randomised trial, and it is also a dose-finding study whose own primary endpoint was measured at 24 weeks, with no active comparator.

In type 2 diabetes, phase 2 reported HbA1c falling by about two percentage points on the higher doses, against essentially no change on placebo56. The published phase 3 diabetes trial, 537 people over 40 weeks, reported a 1.94 percentage point fall on the highest dose and a 15.3 per cent reduction in body weight6. Note that this is a diabetes trial: it does not establish anything about treating obesity.

A substudy of 98 people measured liver fat by MRI and found reductions of roughly 82 per cent on the higher doses7. The authors set out their own limitations plainly, including the absence of biopsies and missing imaging for more than half the participants at 48 weeks.

Why the phase 3 silence matters

Two phase 3 obesity trials completed in 2026, one with 2,335 participants and one with 1,152910. Neither has posted results on the trial registry and neither has been published. Until they report, the best obesity evidence for retatrutide is still that 338-person phase 2.

This is also why claims that retatrutide produces the largest weight loss of any drug, or that it beats tirzepatide or semaglutide, are not supportable42. Both head-to-head trials are still running and unreported. FDA has cited exactly this style of claim in a warning letter to a seller1214.

What the trials reported about side effects

Gastrointestinal effects are the most common and are dose-related, and were the reason 2 to 5 per cent of participants stopped treatment in the phase 3 trial, against none on placebo456. Heart rate rises on retatrutide, by around three and a half beats per minute when trials are pooled413. The phase 2 diabetes trial reported no severe low blood sugar and no deaths56.

What a change in heart rate means over years is exactly the question the cardiovascular and kidney outcomes trial is designed to answer, and that trial is not due to finish until 20291113.

How long it stays in the body

Human pharmacokinetics are published. Levels rise in proportion to the dose and the half-life is about six days, which is why the trials dose once weekly8. No published study covers kidney or liver impairment.

Regulatory and sports status

FDA states that retatrutide cannot be used in compounding, is not a component of any FDA-approved drug, and has not been found safe and effective for any condition112. The agency has warned telehealth companies marketing it to consumers, ingredient distributors supplying it, and sellers labelling it for research use while shipping it with dosing instructions1214. A published case report describes a man with type 1 diabetes becoming seriously unwell after taking retatrutide bought online, alongside a confirmed gut infection that makes cause impossible to establish1214.

For athletes: retatrutide is not named on the 2026 WADA Prohibited List, but section S0 covers substances with no regulatory approval for human use, and those are prohibited at all times3.

What is not known

  • Cardiovascular and kidney outcomes, until the outcomes trial reports1113.
  • Long-term safety: the longest published exposure is 48 weeks46.
  • Obesity phase 3 efficacy and safety, which exist but are unreported910.
  • What happens after stopping[unverified].
  • How it compares directly with tirzepatide or semaglutide42.

Where the rest of the detail lives

The interactive library on the homepage carries the fuller reference entry for retatrutide, including the amounts, schedules and handling notes it holds for every compound. That is general reference information, the same for every visitor.

Open the full retatrutide reference in the library

References

These are the sources behind this page, listed so you can read them yourself rather than take our word for it. Animal and laboratory findings do not establish that something works or is safe in people. Doses and protocols shown on a study card are that study's research parameters, not recommendations. PepCaddie does not sell peptides and does not choose a dose for anyone; this is educational material and it does not replace a qualified healthcare professional.

  • Phase 2 obesity trial

    2023

    Human randomised trial

    Adults with obesity, or overweight with a weight-related condition1 mg to 12 mg once weekly, subcutaneous, as reported in this trial studied48 weeksBody-weight change outcome

    The dose above is the amount used in this study. It is research information, not a recommended dose, and PepCaddie does not convert study doses into human doses.

    This is the trial behind almost every retatrutide figure quoted online. Over 48 weeks, mean body weight fell by 24.2 per cent in the 12 mg group and 22.8 per cent in the 8 mg groups, against 2.1 per cent on placebo. The trial’s own primary endpoint was measured earlier, at 24 weeks, where the 12 mg figure was 17.5 per cent. Gastrointestinal effects were the most common adverse events and were dose-related, and heart rate rose in a dose-dependent way, peaking at 24 weeks before declining.

    Limitation: A 338-person dose-finding trial with a 24-week primary endpoint, compared only against placebo, so it supports no comparison with any other medicine. The abstract reports no confidence intervals, and the 4 mg and 8 mg figures pool two different escalation schedules.

    Randomised, double-blind, placebo-controlled phase 2 trialView study: Phase 2 obesity trial

  • Phase 2 type 2 diabetes trial

    2023

    Human randomised trial

    Adults aged 18 to 75 with type 2 diabetes0.5 mg to 12 mg once weekly, against dulaglutide 1.5 mg, as reported in this trial studied24 weeks, with secondary endpoints at 36 weeksBlood-sugar control outcome

    The dose above is the amount used in this study. It is research information, not a recommended dose, and PepCaddie does not convert study doses into human doses.

    HbA1c fell by about 2 per cent on the higher doses at 24 weeks, against essentially no change on placebo and 1.41 per cent on dulaglutide 1.5 mg. The differences against placebo were statistically significant for every dose except the lowest. Gastrointestinal events were the main adverse events, affecting 35 per cent of participants given retatrutide, and the trial reported no severe hypoglycaemia and no deaths.

    Limitation: Conducted entirely in the United States in a population that was 84 per cent White, which limits how widely the results generalise. The active comparator was a mid-range dose of an older medicine, so it says nothing about how retatrutide compares with current best-in-class treatments.

    Randomised, double-blind, placebo and active-controlled phase 2 trialView study: Phase 2 type 2 diabetes trial

  • Phase 3 type 2 diabetes trial (TRANSCEND-T2D-1)

    2026

    Human randomised trial

    Adults with type 2 diabetes not controlled by diet and exercise alone4 mg, 9 mg or 12 mg once weekly, as reported in this trial studied40 weeksBlood-sugar control outcome

    The dose above is the amount used in this study. It is research information, not a recommended dose, and PepCaddie does not convert study doses into human doses.

    The only phase 3 trial of retatrutide published so far, and it is a diabetes trial rather than an obesity one. HbA1c fell by 1.94 per cent on 12 mg against 0.81 per cent on placebo, and body weight fell by 15.3 per cent against 2.6 per cent. Discontinuation because of adverse events ran at 2 to 5 per cent on retatrutide and none on placebo.

    Limitation: Forty weeks, placebo-controlled only, and in people taking no other diabetes medicine. It is a blood-sugar trial, so it does not support claims about treating obesity.

    Randomised, double-blind, placebo-controlled phase 3 trialView study: Phase 3 type 2 diabetes trial (TRANSCEND-T2D-1)

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