Retatrutide: Benefits, Dosage, Side Effects and Legal Status

Retatrutide (development code LY3437943) is a synthetic peptide built to activate three hormone receptors at once. Its results are striking: in its largest trial, Lilly reports an average 28.3% weight loss at the top dose, against 2.2% on placebo. Unlike most compounds on this site, it has been tested in large, placebo-controlled human trials. It is not yet approved for anything, anywhere.

This page covers what those trials reported, who reported it, and what people using it outside the trials describe.

Dosing: what the studies used.

What is Retatrutide?

Semaglutide activates one receptor (GLP-1). Tirzepatide activates two (GLP-1 and GIP). Retatrutide is built to activate three: GLP-1, GIP and the glucagon receptor.

The trial sponsor, Eli Lilly, says the added glucagon activity is meant to raise energy expenditure and liver-fat metabolism, on top of the appetite and insulin effects of the other two receptors. That is Lilly’s design rationale and a real pharmacological hypothesis. It has not been shown in an approved product, because none exists yet.

Retatrutide structure

Molecular formula

C₂₂₁H₃₄₂N₄₆O₆₈

Molecular weight

4731.4 g/mol

Length

39 amino acids

Sequence

YXQGTFTSDYSILLDKKAQXAFIEYLLEGGPSSGAPPPS

Modifications

X at positions 2 and 20 = Aib; Leu13 is alpha-methyl-L-leucine; Lys17 carries a C20 fatty diacid via gamma-Glu and one OEG unit; C-terminal amide.

PubChem has no parent record for retatrutide with correct stereochemistry; the correctly configured one (CID 171934787) is titled as the sodium salt, so no diagram is shown.

Sequence checked against Cell Discovery (2024), structural study of retatrutide.

What the trials actually show

Retatrutide’s biggest completed study is TRIUMPH-1, a Phase 3, randomised, double-blind, placebo-controlled trial. It enrolled 2,335 people with obesity or overweight but without type 2 diabetes, and its main outcome was weight change at 80 weeks. ClinicalTrials.gov lists it as completed, but no results have been posted there and no peer-reviewed paper exists yet.

What exists is a company press release. Eli Lilly announced topline TRIUMPH-1 results on 21 May 2026:

Side effects and dropouts also rose with dose, as the side-effects section sets out.

Peer-reviewed results do exist from other trials. A 48-week Phase 2, randomised, double-blind, placebo-controlled trial in 338 adults with obesity or overweight was published in the New England Journal of Medicine in 2023. Mean weight change by weekly dose was:

• 1 mg: -8.7%
• 4 mg: -17.1%
• 8 mg: -22.8%
• 12 mg: -24.2%
• Placebo: -2.1%

On 12 mg, 83% of people lost at least 15% of their body weight, against 2% on placebo. The Phase 3 TRANSCEND-T2D-1 diabetes trial, covered below, has also been published.

Lilly is also running TRIUMPH-Outcomes, a Phase 3 trial in roughly 10,000 people with obesity and cardiovascular or kidney disease. It tests whether retatrutide reduces serious cardiovascular events or slows the decline in kidney function. It is still active and has not reported results.

Retatrutide benefits: what the research shows

More from TRIUMPH-1. Lilly’s 21 May 2026 press release reports that 45.3% of people on 12 mg lost at least 30% of their body weight by 80 weeks. The release compares that with outcomes typical of bariatric surgery. In a study extension, people who started with a BMI of 35 or higher lost an average of 85.0 lb (30.3%) by 104 weeks.

Other Phase 3 trials:

• TRIUMPH-2 (obesity or overweight with type 2 diabetes) and TRIUMPH-3 (severe obesity with cardiovascular disease) reported further weight-loss figures by dose at 80 weeks. TRIUMPH-2 also showed an average A1C reduction of up to 1.6%, per Lilly’s 23 July 2026 press release. Lilly plans to include these in a Biologics License Application to FDA in the first quarter of 2027. That filing is planned, not submitted or approved.
• TRANSCEND-T2D-1 (537 adults with type 2 diabetes not controlled by diet and exercise, 40 weeks) was published in The Lancet in June 2026. HbA1c fell by 1.69 to 1.94 percentage points across the 4, 9 and 12 mg doses, against 0.81 on placebo. Body weight fell by 11.5% to 15.3%, against 2.6% on placebo. Lilly’s 6 June 2026 press release gave higher figures (A1C down by up to 2.0%, weight down by up to 16.8%, or 36.6 lb) from a different analysis. The paper’s main (treatment-regimen) estimates given here are the peer-reviewed ones.
• TRIUMPH-1 sub-studies in knee osteoarthritis and moderate-to-severe obstructive sleep apnea were presented at the same ADA meeting, per the same release. WOMAC knee-pain scores fell by up to 4.3 points (73.1%) from a baseline of 6.0. Sleep-apnea severity (apnoea-hypopnoea index) fell by up to 36.1 events per hour (60.6%) from a baseline of 58.6. The release doesn’t say these were published in a peer-reviewed journal.

Half-life: about 6 days

In a 12-week Phase 1b trial in 72 people with type 2 diabetes, published in The Lancet in 2022, retatrutide’s half-life was about 6 days. Its blood levels rose in proportion to dose, and the investigators said this suggests it suits once-weekly dosing. The figure applies to the trial’s own drug; it says nothing about a vial sold outside the trials.

What people who use it report

Retatrutide is now used well beyond Lilly’s trials. CBS News reported in July 2026 that it has gone viral online and was being sold by online vendors, some clinics and even Brooklyn convenience stores. FDA has warned telehealth companies and ingredient distributors over it, as the legal section sets out. The self-reports I found point in more than one direction:

• Strong results. Many users and some medical professionals told CBS News they had seen great results, which is what is driving demand.
• A different side-effect pattern from the trials. A preprint, not yet peer reviewed, analysed Reddit posts from 13,589 people describing current use (Sehgal and colleagues, medRxiv 2026). The most common symptoms were increased appetite, fatigue, increased energy, nausea, food cravings, insomnia and a raised heart rate. In the trials, gut effects dominated. The authors say product quality, dose variability, stacking with other peptides or misattribution could explain some of the difference.
• Hospital cases. CBS reports that America’s Poison Centers has tracked a sharp rise in toxicity reports attributed to retatrutide. One published case describes a man with type 1 diabetes who needed hospital treatment for severe vomiting, high ketones and acute kidney injury shortly after taking an online product sold as retatrutide. His partner, who took the same product, also had stomach symptoms, and a Shigella infection found later means the cause can’t be settled Branine 2026 - Branine N. Online-Sourced Retatrutide Complicating Impending Diabetic Ketoacidosis in a Patient With Type 1 Diabetes and Concurrent Shigella Gastroenteritis. Cureus. 2026;18(8):e115260., in the references below.

Self-reports can’t separate the drug from placebo, diet changes or anything else people did at the same time. With a grey-market vial, no one can confirm what was injected. That is why the trial data remain the evidence that counts.

Retatrutide dosage

There is no approved dose, because there is no approved product. What follows is the sponsor’s trial design, not a recommendation.

TRIUMPH-1 tested three weekly doses against placebo for 80 weeks: 4 mg, 9 mg and 12 mg. Lilly reported that weight loss, gut side effects and dropouts all rose with dose (see the table above and the side-effects section). That pattern is how a Phase 3 programme compares a range of exposure, not a personal dosing guide.

Retatrutide side effects

Retatrutide has no FDA label, so there is no regulator-reviewed list of side effects. What exists comes from published Phase 2 and Phase 3 trials, all funded by the developer, and Lilly’s topline TRIUMPH-1 data.

• Gut effects were the most common in TRIUMPH-1: nausea, diarrhoea, constipation and vomiting. Lilly’s release didn’t give a rate for each.
• Dropouts rose with dose. Stopping because of side effects was 4.1% at 4 mg, 6.9% at 9 mg and 11.3% at 12 mg, against 4.9% on placebo, the same pattern as the weight loss.
• In the Phase 2 obesity trial, gut effects were the most common side effects. They rose with dose, were mostly mild to moderate, and were partly reduced by starting at 2 mg rather than 4 mg. Heart rate also rose with dose, peaking at 24 weeks and falling after that.
• In TRANSCEND-T2D-1, 2% to 5% of people on retatrutide stopped because of side effects, against 0% on placebo. Gut effects eased over time, and no severe hypoglycaemia (low blood sugar) was reported. Two deaths, both in the 4 mg group, were judged unrelated to the drug.

This pattern matches the approved GLP-1-class drugs covered on this site, as expected from the shared GLP-1 mechanism. It is not a finding about retatrutide’s added GIP and glucagon activity. There is no long-term safety data beyond the trials, and FDA has reviewed none of it.

Get medical care for severe or persistent abdominal pain, persistent vomiting, or signs of gallbladder trouble. Those are reasons to stop and see a doctor with other GLP-1-class drugs; for retatrutide this is inferred from the shared mechanism, not shown in its own trials. For the injection itself, see injection-site reactions. See dosing for what the trials tested.

Is Retatrutide legal?

FDA has named retatrutide directly. In its published concerns about unapproved GLP-1 drugs, it says retatrutide and cagrilintide cannot be used in compounding under federal law. Neither is part of an FDA-approved drug, and neither has been found safe and effective for any condition. FDA has warned:

• telehealth companies for marketing unapproved drugs including retatrutide
• active pharmaceutical ingredient distributors for selling it to compounders
• outsourcing facilities for repackaging it.

Related

• Semaglutide (Ozempic, Wegovy)
• Tirzepatide (Mounjaro, Zepbound)
• Cagrilintide - the amylin analogue developed alongside it
• Best GLP-1 for weight loss: the approved options compared
• How GLP-1 medicines work
• Are peptides safe?

Regulatory changes for this compound and others, as they happen: US peptide regulation tracker.

How Retatrutide compares

GLP-1 and related medicines. Doses for unapproved compounds are common practice, not trial-established. All weight loss and metabolism peptides →

Compound	Main use	Evidence	Usual dose	US status
Retatrutide	Investigational in Phase 3 trials for obesity, type 2 diabetes and related conditions. Not approved for any indication in the US. Sold outside the trial system as an unapproved research chemical, often alongside semaglutide and tirzepatide.	Moderate human evidence	2-12 mg, once weekly, starting at 2 mg and titrating up every 4 weeks to a 4-12 mg maintenance dose	Research use only
Semaglutide	FDA-approved for type 2 diabetes in adults (Ozempic injection and tablets, Rybelsus), including cardiovascular risk reduction and, for the Ozempic injection, kidney-disease progression; and as Wegovy injection and tablets for chronic weight management and cardiovascular risk reduction in adults with obesity or overweight. The Wegovy injection is also approved for weight management from age 12 and for MASH with moderate to advanced liver fibrosis in adults.	Strong human evidence	FDA label	FDA-approved · prescription only
Tirzepatide	FDA-approved to improve glycemic control in type 2 diabetes in adults and children 10 years and older, and to reduce cardiovascular risk in adults with type 2 diabetes (Mounjaro), and for chronic weight management and moderate-to-severe obstructive sleep apnoea in adults with obesity (Zepbound).	Strong human evidence	FDA label	FDA-approved · prescription only
Liraglutide	FDA-approved as a once-daily injection under two brands: Saxenda, for chronic weight management alongside diet and exercise in adults and in children 12 years and older with obesity who weigh more than 60 kg, and Victoza, for glycemic control in type 2 diabetes in adults and children 10 years and older, and for reducing major adverse cardiovascular events in adults with type 2 diabetes and established cardiovascular disease.	Strong human evidence	FDA label	FDA-approved · prescription only
Orforglipron	FDA-approved as Foundayo, in combination with a reduced-calorie diet and increased physical activity, to reduce excess body weight and maintain weight reduction long term in adults with obesity, or adults with overweight who have at least one weight-related condition.	Strong human evidence	FDA label	FDA-approved · prescription only
Survodutide	An investigational injectable peptide, not approved for any use. Its sponsor, Boehringer Ingelheim, is studying it in Phase 3 trials for chronic weight management and, in a separate programme, for MASH (metabolic dysfunction-associated steatohepatitis). It is also sold directly to consumers as a research chemical outside those trials.	Moderate human evidence	0.6-6 mg, once weekly, starting around 0.6 mg; the phase 2 trial titrated over about 20 weeks to a 2.4-4.8 mg maintenance dose, while the published phase 3 SYNCHRONIZE-1 trial randomizes to a higher 3.6 or 6.0 mg maintenance target using a slower, flexible up-titration	Research use only
Mazdutide	Approved in China for chronic weight management and for glycemic control in type 2 diabetes. Not FDA-approved in the United States, where it is sold to consumers as a research-chemical vial.	Moderate human evidence	3-9 mg, once weekly, titrated upward from a lower starting dose	Research use only
Cagrilintide	Investigational amylin analogue studied alone and, more prominently, combined with semaglutide as the fixed-dose combination CagriSema, for chronic weight management. Not approved for any indication in the US; the combination is under FDA review following the sponsor's New Drug Application.	Moderate human evidence	0.25-4.5 mg, once weekly, titrating from a 0.25-0.6 mg starting dose up to a 2.4-4.5 mg maintenance dose	Research use only

Where to buy Retatrutide for research

Each vendor is checked against my vendor checklist.

1. 1.Next Level PharmFeatured

   10 mg vial

   • No FDA warning letter found
   • Names its testing lab
   • Batch COAs published
   • Takes card payment

   $63.99as of 3 October 2026

   View product →My Next Level Pharm review

2. 2.Spartan Peptides

   GLP-3(Reta) 6 mg vial

   • No FDA warning letter found
   • Names its testing lab

   $180.00as of 3 October 2026

   View product →My Spartan Peptides review

Compare every checked vendor for Retatrutide →

See all vendors and how they compare →

Common questions

Is retatrutide FDA-approved?

No. Retatrutide has no FDA-approved product and no approved indication. Most of its Phase 3 programme has reported only topline results; one Phase 3 diabetes trial, TRANSCEND-T2D-1, has been published in The Lancet. FDA has also said it cannot legally be compounded, because it is not part of an FDA-approved drug and has not been found safe and effective for any condition.

What makes retatrutide different from semaglutide and tirzepatide?

The number of receptors it activates. Semaglutide activates GLP-1 alone, tirzepatide activates GLP-1 and GIP, and retatrutide adds the glucagon receptor, which neither approved drug targets. Lilly's rationale is that glucagon activity adds energy-expenditure and liver-fat effects. That is the sponsor's design rationale, not something shown in an approved human study.

What do the retatrutide trials actually show so far?

Eli Lilly's press release on TRIUMPH-1, a completed Phase 3 trial of 2,335 people, reported average weight loss over 80 weeks of 19.0% at 4 mg, 25.9% at 9 mg and 28.3% at 12 mg, against 2.2% on placebo. Those figures have not been posted to the trial registry, peer reviewed or reviewed by FDA. Peer-reviewed results do exist: a 48-week Phase 2 obesity trial (New England Journal of Medicine, 2023) reported 24.2% weight loss on 12 mg against 2.1% on placebo. The 40-week TRANSCEND-T2D-1 diabetes trial (The Lancet, 2026) reported 11.5% to 15.3% across doses, against 2.6% on placebo.

Can I buy retatrutide legally as a research chemical?

You can buy a vial from a grey-market seller, but FDA has said retatrutide is not eligible for compounding under federal law. It has warned telehealth companies, ingredient distributors and outsourcing facilities specifically over unapproved retatrutide. A product sold this way has none of the quality control, labelling accuracy or safety review of an FDA-approved drug.

When might retatrutide be FDA-approved?

I don't know, and I won't guess a date. Eli Lilly has reported topline Phase 3 obesity results and is running a roughly 10,000-person cardiovascular and kidney outcomes trial. In August 2026 it said it plans to submit an FDA marketing application in the first quarter of 2027, with FDA review to follow. Nothing on this page predicts approval or a timeline.

What are the side effects of retatrutide?

There is no FDA label, so the data come from published Phase 2 and Phase 3 trials and Lilly's own topline TRIUMPH-1 report. In all of them, gut effects such as nausea, diarrhoea and vomiting were the most common. In TRIUMPH-1, stopping because of side effects rose with dose, from 4.1% at 4 mg to 11.3% at 12 mg, against 4.9% on placebo; the Phase 2 obesity trial found a dose-related rise in heart rate that peaked at 24 weeks. That matches approved GLP-1-class drugs, but there is no long-term safety data and FDA has reviewed none of it.

What are the cons of taking retatrutide?

No regulator has reviewed its safety or effectiveness for any condition, and federal law does not allow it to be compounded. Its largest obesity trial has reported only the company's topline figures, and the peer-reviewed results so far all come from developer-sponsored trials. In TRIUMPH-1, gut side effects (nausea, diarrhoea, constipation, vomiting) were most common, and stopping because of side effects rose from 4.1% at 4 mg to 11.3% at 12 mg, against 4.9% on placebo. There is no long-term safety data, and a vial sold outside the trials carries none of their quality control.

Why am I not losing weight on retatrutide?

I can't diagnose an individual result, but two things are worth knowing. A trial average blends a range of outcomes: at any dose some people lost more and some less, and the average doesn't say where one person falls. Retatrutide bought outside Lilly's trials is not made, tested or dosed to the same standard, and no regulator checks that it matches its label. If this is a live medical question for you, it belongs with a licensed prescriber.

Why is retatrutide the best?

There is no evidence-based ranking of retatrutide, semaglutide and tirzepatide. Retatrutide is not FDA-approved: its published results come from a Phase 2 trial and one Phase 3 diabetes trial, and its largest obesity trial has reported only company topline figures. Semaglutide and tirzepatide are approved medicines with trial evidence reviewed for specific uses, covered on this site's semaglutide and tirzepatide pages. A bigger weight-loss figure in an early trial is not approval, and not proof that one drug is better for a given patient.

What is the usual retatrutide dose?

There is no approved dose, because there is no approved product. Clinic and dosing-guide sources describe once-weekly injections under the skin, starting at 2 mg and stepping up every 4 weeks to a 4-12 mg maintenance dose, mirroring the Phase 3 schedule. That is common practice, not an approved dose. A published Phase 2 trial tested 1, 4, 8 and 12 mg weekly; see the full dosage page for that table.

Is retatrutide the same as Ozempic?

No. Ozempic is semaglutide, an FDA-approved drug that activates one receptor, GLP-1. Retatrutide is a different, investigational molecule that activates three (GLP-1, GIP and glucagon) and is not approved for anything. The section on what retatrutide is, above, sets out the difference.

When will retatrutide be available?

There is no approval or launch date. Eli Lilly said in August 2026 that it plans to submit an FDA marketing application in the first quarter of 2027, and FDA review would follow. Until then Lilly supplies it only through its trials and, since August 2026, a limited early-access programme for some people with severe obesity who cannot join a trial. Vials sold online as research retatrutide are not the trial drug and carry none of its quality control.

What well-known people have said about Retatrutide

Public statements, shown because people search for them. Each is one person's account, in their words or a faithful summary, with where and when they said it. None of it is evidence that Retatrutide works or is safe; that is what the rest of this page is for.

• 

  Andrew Hubermanneuroscientist and podcast hostDiscussed it

  On Gwyneth Paltrow's goop podcast, Huberman described retatrutide as a milder GLP-1 agonist that also acts on glucagon and GIP, with a lower side-effect profile and what seems to be some muscle-sparing effect. He did not say he uses it.

  “Retatrutide is a more mild agonist of GLP-1.”

  The goop Podcast with Gwyneth Paltrow (episode published 10 March 2026), as reported by Fox News on 20 May 2026, 10 March 2026. Source: Fox News · Apple Podcasts (official episode listing, the goop podcast)

  Photo: Jamesbrianbounds, CC BY-SA 4.0, via Wikimedia Commons

References (12 sources)

Show

Bibliographic detail is fetched from PubMed, not written by me - so a citation here cannot drift from the paper it names. Study design comes from PubMed's own tags rather than my judgement.

1. 1.Jastreboff AM, Kaplan LM, Frías JP et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial. N Engl J Med. 2023;389(6):514-526.Randomised trialPMID 37366315
2. 2.Bajaj HS, Welch M, Shah P et al. 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. Lancet. 2026;407(10546):2402-2413.Randomised trialPMID 42250575
3. 3.Urva S, Coskun T, Loh MT et al. 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. Lancet. 2022;400(10366):1869-1881.Randomised trialPMID 36354040
4. 4.Branine N. Online-Sourced Retatrutide Complicating Impending Diabetic Ketoacidosis in a Patient With Type 1 Diabetes and Concurrent Shigella Gastroenteritis. Cureus. 2026;18(8):e115260.Case reportPMID 42669023full text
5. 5.FDA - retatrutide and cagrilintide cannot be used in compounding under federal law; not components of FDA-approved drugs and not found safe and effective for any condition; enforcement against telehealth companies, API distributors and outsourcing facilities.- US Food and Drug Administrationregulatory
6. 6.Eli Lilly second-quarter 2026 results (SEC Form 8-K exhibit, 5 August 2026): plans to submit a Biologics License Application for retatrutide to the U.S. FDA in the first quarter of 2027.- Eli Lilly and Company, via US Securities and Exchange Commissionother
7. 7.AJMC - Lilly Expands Retatrutide Access Amid Doctor Pushback (5 August 2026): Lilly confirmed an early-access programme for adults with refractory obesity and serious complications who cannot take part in clinical trials.- The American Journal of Managed Careother
8. 8.CBS News, 2 July 2026 - What a Brooklyn bodega reveals about the craze for an experimental weight-loss drug. Retatrutide has gone viral online; many users and some clinicians report great results, alongside reports of concerning side effects and a sharp rise in poison-centre reports.- CBS Newsnews
9. 9.Sehgal, Tronieri, Rader, Ungar and Guntuku - Self-Reported Side Effects Among Reddit Users Taking Unapproved Retatrutide (medRxiv preprint, 2026, not peer reviewed). Analysis of posts from 13,589 Reddit users describing current retatrutide use, 2023-2025.- medRxiv (University of Pennsylvania and Boston Children's Hospital authors)survey
10. 10.21 May 2026 press release- PR Newswire (company press release)news
11. 11.23 July 2026 press release- PR Newswire (company press release)news
12. 12.6 June 2026 press release- PR Newswire (company press release)news

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