Retatrutide (reta): trials, side effects and doses used in studies

In short

Retatrutide is a peptide drug from Eli Lilly acting on the GIP, GLP-1 and glucagon receptors, studied for obesity and type 2 diabetes. In large randomised trials weight fell substantially, but it has no marketing authorisation in the EU or the US [3, 13, 14]A [20, 21]regulator.

• Retatrutide (code LY3437943) is an investigational drug being developed as a prescription medicine, studied as a once-weekly injection under the skin [1, 14]A.
• In TRIUMPH-1, 2,339 adults with obesity lost a mean of 17.6% to 25.0% of body weight over 80 weeks depending on the dose, against 3.9% on placebo [14]A.
• Weaknesses: stomach symptoms were common, heart rate rose with dose, and in TRIUMPH-2 12% of the 9 mg group and 5% of the placebo group stopped treatment because of adverse events or death [1, 13]A. All large trials were funded by the manufacturer [1, 3, 13, 14]A.
• There is no marketing authorisation in the EU or the US [20, 21]regulator. Vials sold online as "reta" or "GLP-3 RT" are unapproved products whose content can differ from the label [7]regulator [16]D.
• In sport retatrutide falls under WADA class S0, which is prohibited at all times [9]regulator.

What is retatrutide?

Retatrutide (code LY3437943) is a single peptide that activates three hormone receptors: GIP (glucose-dependent insulinotropic polypeptide), GLP-1 (glucagon-like peptide 1) and glucagon [1, 2]A. That is why it is called a triple agonist. It has been studied as a once-weekly injection under the skin [1]A.

For comparison, semaglutide acts on the GLP-1 receptor and tirzepatide on the GIP and GLP-1 receptors [34]A. Retatrutide adds the glucagon receptor [1]A.

Retatrutide is an investigational drug. It has no marketing authorisation in the EU [21]regulator, and according to the FDA it has not been found safe and effective for any condition [20]regulator. On social media it is called "reta", and online shops have sold it under names such as "GLP-3 RT" [7]regulator. "GLP-3" is not the name of any medicine, and such a product is not the drug used in the trials. All GLP-1 medicines: Weight-loss drugs (GLP-1).

Evidence at a glance

Each cell gives the kind of study and its source. The letter is the evidence level, not the result.

"-" = no such study is known.

What is retatrutide studied for?

Retatrutide is studied mainly for obesity and type 2 diabetes [3, 13, 14]A. It is not approved for any of these [20, 21]regulator.

• Obesity and overweight: the TRIUMPH programme, which also covers knee osteoarthritis and sleep apnoea [4] [14]A.
• Type 2 diabetes: the TRANSCEND-T2D trials [3]A [6]E, not peer-reviewed.
• Fatty liver disease (MASLD): a phase 2 substudy [12]A and an ongoing phase 3 trial [6]E, not peer-reviewed.
• Heart and kidney events, kidney impairment and low back pain: ongoing phase 3 trials, no results yet [6]E, not peer-reviewed.

The manufacturer, Eli Lilly, says it plans to apply for US approval in the first quarter of 2027 [5]E, not peer-reviewed. An application is not an approval.

How does retatrutide work?

Retatrutide acts on the receptors of three gut and pancreatic hormones. In cells it activated the GIP receptor more strongly than the GLP-1 and glucagon receptors, which it activated about equally [10]D.

In obese mice the GIP and GLP-1 effects reduced eating, and the glucagon receptor increased energy expenditure. Together they lowered weight further [10]C. It is not known how much of the weight loss in humans comes from each receptor.

In humans the fall in liver fat was linked to weight loss, less abdominal fat and better insulin sensitivity [12]A. In a body composition study fat mass fell, and the share of lean tissue in the weight lost was similar to other obesity treatments [15]A.

Has retatrutide been studied in humans?

Yes. Randomised, placebo-controlled trials of retatrutide from phases 1 to 3 have been published. The trials covered on this page include more than 4,500 participants in total [1, 2, 3, 11, 13, 14]A. Some phase 3 results exist so far only as a company press release [5]E, not peer-reviewed.

Obesity without diabetes: TRIUMPH-1 (phase 3)

2,339 adults with obesity and without diabetes received retatrutide 4, 9 or 12 mg or placebo once a week for 80 weeks. Mean weight fell by 17.6% (4 mg), 23.7% (9 mg) and 25.0% (12 mg), against 3.9% on placebo [14]A.

In the subgroup with knee osteoarthritis (574 people) pain scores fell more than on placebo, and in the subgroup with sleep apnoea (243 people) breathing pauses per hour fell more than on placebo. The most common adverse events were gastrointestinal [14]A.

Obesity and type 2 diabetes: TRIUMPH-2 (phase 3)

1,152 adults with a BMI of at least 27 and type 2 diabetes received retatrutide or placebo for 80 weeks. Weight fell by 11.9% (4 mg), 16.8% (9 mg) and 18.8% (12 mg), against 5.1% on placebo [13]A.

Lilly's press release gave a top figure of 20.8% [5]E, not peer-reviewed. The difference comes from the method: the release assumes everyone stayed on the drug, while the published trial counts all participants, including those who stopped [5]E, not peer-reviewed [13]A.

Obesity and cardiovascular disease: TRIUMPH-3 (press release only)

According to Lilly, 1,949 people with severe obesity and cardiovascular disease lost 21.6% (9 mg) and 22.6% (12 mg) of body weight over 80 weeks, against 3.2% on placebo [5]E, not peer-reviewed. As of 13 Oct 2026 the results had not been published in a peer-reviewed journal.

Type 2 diabetes: phase 2 and TRANSCEND-T2D-1

In the phase 2 trial 281 people with type 2 diabetes received retatrutide, placebo or dulaglutide 1.5 mg. HbA1c, the long-term blood sugar measure, fell by up to 2.02 percentage points over 24 weeks, and more than with dulaglutide on the highest doses [2]A.

In the phase 3 TRANSCEND-T2D-1 trial, 537 adults whose diabetes was managed with diet and exercise alone received retatrutide or placebo for 40 weeks. HbA1c fell by 1.69 to 1.94 percentage points (placebo 0.81) and weight by 11.5% to 15.3% (placebo 2.6%). No severe hypoglycaemia was reported [3]A.

Obesity: the phase 2 trial

338 adults received retatrutide 1 to 12 mg or placebo for 48 weeks. Weight fell by 8.7% on the lowest and 24.2% on the highest dose, against 2.1% on placebo. In the 12 mg group 83% lost at least 15% of body weight, against 2% on placebo [1]A.

Liver fat and body composition

98 participants in the phase 2 obesity trial had fatty liver. Over 24 weeks liver fat fell by 42.9% (1 mg) to 82.4% (12 mg), while it rose by 0.3% on placebo. Normal liver fat was reached by 86% of the 12 mg group and by nobody on placebo [12]A.

In a body composition substudy in people with diabetes, fat mass fell by 23.2% to 26.1% over 36 weeks on the highest doses, against 4.5% on placebo [15]A. Only 103 people who had both scans were measured [15]A.

Promising, but only in animal and cell studies

These findings concern only mice or cells. They have not been studied in humans, and an animal result cannot be carried over to humans.

• Obesity-related cancer no human studies

  In obese mice, weight loss on retatrutide was linked to slower tumour growth and a 14-fold smaller tumour in a pancreatic cancer model. In a lung cancer model tumour engraftment was halved [30]C.

  If it held in humans: the cancer risk of people with obesity treated with retatrutide might fall through weight loss and the immune response.

  Why it might not translate: In mouse cancer models the tumour is implanted into the animal, which does not match how cancer develops in humans. There is one study, and it has not been repeated.

  Evidence now: One mouse study [30]C. Cancer risk has not been studied in humans as a trial of its own.

• Kidney scarring no human studies

  In mice retatrutide reduced kidney scarring and inflammation, and in kidney cells it blocked cell pathways linked to inflammation. At the doses tested the effect was larger than with semaglutide and tirzepatide [31]C.

  If it held in humans: retatrutide might slow kidney damage, also without diabetes.

  Why it might not translate: In the model kidney damage is caused by blocking the ureter, which does not match chronic kidney disease in humans. The authors themselves describe the results as a source of hypotheses.

  Evidence now: One mouse and cell study [31]C. Kidney effects are being studied in humans in ongoing trials with no results yet [6]E, not peer-reviewed.

Who studies retatrutide?

Retatrutide is developed and studied by Eli Lilly. The phase 1 to 3 trials were funded by Lilly [1, 2, 3, 11, 13, 14, 15]A, and all 14 phase 3 trials in the registry are Lilly's [6]E, not peer-reviewed. Company employees are among the authors [1, 2, 3, 12]A. That is normal in drug development, but worth knowing.

Case reports on users of unverified products obtained outside medical care [17, 18]B, an analysis of products sold in Australia [16]D and an anti-doping method study [25]B have also been published.

Author of this page: the editorial team

This page was written by the Molecular Recovery editorial team. The draft was made with the help of AI, and the claims were checked against the sources (AI policy). The page has not been medically reviewed. How we work: About us.

How long does retatrutide stay in the body?

The half-life of retatrutide is about 6 days, and blood levels rose in proportion to the dose. That is why it has been studied as a once-weekly drug [11]A.

In an anti-doping study four users injected 2 mg themselves on days 1 and 7. Retatrutide could be detected in blood for about 56 days after the first injection, but it was not found in urine [25]B.

What side effects does retatrutide have?

The most common side effects are gastrointestinal: diarrhoea, nausea, vomiting and constipation. They were mostly mild to moderate [1, 2, 3]A. In the phase 2 obesity trial they increased with dose and were partly reduced by a lower starting dose [1]A.

What users report. In the Reddit accounts we compiled (not research), 611 of 1182 people (52%) reported some harm, most often: fatigue (98, 8%), food aversion or eating too little (78, 7%) and nausea (74, 6%). People tend to post when something goes wrong, so this share does not tell how common harms are. Retatrutide has no marketing authorisation, so the accounts are about products bought online whose contents are unknown. 796 of 1329 accounts came from the users' own forum r/Retatrutide, where positive accounts may be over-represented. The harms in detail: Retatrutide user experiences.

What the trials found

• Stomach symptoms: in TRIUMPH-2 diarrhoea occurred in 27% to 34% on retatrutide and 13% on placebo, nausea in 14% to 28% and 8% [13]A.
• Heart rate: in the phase 2 obesity trial heart rate rose with dose, peaked at week 24 and declined thereafter [1]A. In a lab experiment on human atrial tissue retatrutide increased the contraction force of heart muscle [33]D.
• Low blood pressure: 1% to 6% in the retatrutide groups and under 1% on placebo in TRIUMPH-2 [13]A.
• Abnormal skin sensations (dysaesthesia): 4% to 7% in the retatrutide groups and under 1% on placebo in TRIUMPH-2 [13]A.
• Stopping treatment: in TRIUMPH-2, 4% (4 mg), 12% (9 mg) and 8% (12 mg) stopped because of adverse events or death, against 5% on placebo [13]A. In TRANSCEND-T2D-1 the share was 2% to 5%, against 0% on placebo [3]A.
• Deaths: in TRIUMPH-2 six people on retatrutide and one on placebo died, and in TRANSCEND-T2D-1 two in the 4 mg group. According to the investigators none was caused by the drug [3, 13]A.

The placebo group has side effects too, and the comparison shows what the drug adds. In TRIUMPH-2 and TRIUMPH-3 the dose started at 2 mg and was increased stepwise every four weeks [5]E, not peer-reviewed.

Products bought online

In the trials the drug came from the manufacturer, doses were exact and participants were medically monitored. None of that applies to a product bought online or otherwise obtained outside medical care. A woman in her mid-20s was admitted to hospital with nausea that did not respond to treatment after a self-described wellness coach without medical qualifications had given her four injections of an unverified product said to contain retatrutide [17]B. In a man with type 1 diabetes, use of a product bought online was linked to a dangerous rise in ketones; he also had a gut infection at the same time, so the cause is uncertain [18]B.

The Dutch health inspectorate IGJ said it had received several reports of harm after people used retatrutide [22]regulator. More: Side effects and safety.

Interactions and who there is no data for

Retatrutide has no summary of product characteristics because it has no marketing authorisation [21]regulator. Interactions have therefore not been officially compiled.

• Diabetes medicines: in TRIUMPH-2, 92% were on oral diabetes medicines, including sulfonylureas [13]A. No severe hypoglycaemia was reported in the phase 2 trial or TRANSCEND-T2D-1 [2, 3]A.
• Type 1 diabetes: retatrutide has not been studied in type 1 diabetes. In a case report, a product bought online complicated blood sugar management in hospital [18]B.
• Other groups: we know of no study of retatrutide in children or in pregnant or breastfeeding women.

What speaks against it and what is unknown

Weight loss is well shown, but long-term safety, weight after stopping and head-to-head comparisons with other drugs are still missing [6]E, not peer-reviewed [13, 14]A.

Counter-evidence

• In TRIUMPH-2, 12% of the 9 mg group and 5% of the placebo group stopped treatment because of adverse events or death [13]A.
• People with type 2 diabetes lost less weight than people without diabetes: 18.8% and 25.0% on the highest dose [13, 14]A.
• In TRIUMPH-1 the weight difference between 9 mg and 12 mg was small (23.7% and 25.0%) [14]A.
• The company release gives larger figures than the peer-reviewed paper because they are calculated differently [5]E, not peer-reviewed [13]A.

What the evidence does not support

• "Reta is already an approved weight-loss drug": it is not. Retatrutide is not in the EMA medicines list [21]regulator, and according to the FDA it has not been found safe and effective for any condition [20]regulator.
• "Reta bought online is the same as in the trials": in Australia, three products labelled as 10 mg contained 5.13, 16.5 and 19.0 mg of retatrutide [16]D. According to the FDA, products labelled "for research purposes" are of unknown quality [20]regulator.
• "No muscle is lost": the share of lean tissue in the weight lost was similar to other obesity treatments, so lean tissue fell too [15]A.
• "Retatrutide prevents cancer": the finding comes from mice only [30]C.

What is not known

• Safety beyond 80 weeks: the longest published trials lasted 80 weeks [13, 14]A.
• Effect on heart and kidney events: the outcomes trial is ongoing, with primary results listed in the registry for February 2029 [6]E, not peer-reviewed.
• Whether weight returns after stopping: TRIUMPH-6, which studies weight maintenance, is ongoing [6]E, not peer-reviewed.
• Whether retatrutide works better than tirzepatide or semaglutide: head-to-head trials are ongoing [6]E, not peer-reviewed.

Retatrutide doses used in trials

Retatrutide has no approved dosing because it has no marketing authorisation [20, 21]regulator. Below are the doses used in trials. In them the dose was increased stepwise under medical supervision, and they are not dosing guidance.

Animal doses are not in this table because they cannot be converted into human doses.

What the numbers do not tell you. A trial dose says what a group was given as the manufacturer's own product, not what dose would suit anyone. The real amount in a product bought online can differ from the label [16]D. Dose page: Retatrutide doses used in studies. Calculator: unit converter; it only converts units and does not tell you how much is safe to use.

Retatrutide vs tirzepatide vs semaglutide: what is the difference?

The main differences are the receptors and the status: retatrutide acts on three receptors and has no marketing authorisation, tirzepatide on two and semaglutide on one [1, 34]A [21]regulator. No head-to-head trials of retatrutide against tirzepatide or semaglutide have been published yet [6]E, not peer-reviewed.

Why the numbers cannot be compared directly. The trials lasted different lengths of time, and their participants and years differed [14, 28, 29]A. The tirzepatide and retatrutide trials were also funded by the same company [14, 28]A. The only direct comparison with a GLP-1 drug is the phase 2 diabetes trial, in which the highest retatrutide doses lowered HbA1c more than dulaglutide 1.5 mg [2]A.

Head-to-head trials are under way: TRIUMPH-5 compares retatrutide with tirzepatide in obesity (NCT06662383), and TRANSCEND-T2D-2 compares it with semaglutide in type 2 diabetes (NCT06260722) [6]E, not peer-reviewed. All GLP-1 medicines: Weight-loss drugs (GLP-1).

Combinations: retatrutide and cagrilintide

We know of no human study of retatrutide combined with other weight-loss substances. In obese rats, retatrutide combined with cagrilintide lowered weight more than either substance alone [32]C.

A rat experiment does not tell whether the combination is safe for humans or what dose would make sense. According to the FDA, cagrilintide is not a component of any approved drug either [20]regulator. Blends in general: Peptide blends: what is in the vial and why the seller's label is not enough.

Cagrilintide on its own page: cagrilintide alongside retatrutide.

The situation in the United States

The FDA has not approved retatrutide. According to the FDA, retatrutide is not a component of any approved drug, has not been found safe and effective for any condition, and cannot be used in compounding [20]regulator.

• Warnings to sellers: the FDA has warned telehealth companies and active ingredient distributors over retatrutide, as well as companies that sold it labelled "for research purposes" [20]regulator. In August 2026 an FDA warning letter covered a product called "GLP-3 RT (Retatrutide) Research Peptide", which the FDA said was an unapproved drug [7]regulator.
• Expanded access: in June 2026 Lilly registered a single-patient pre-approval access programme. It is meant for adults with a BMI of at least 35, at least two serious obesity-related complications and no response to approved treatments [27]E, not peer-reviewed.
• Application: Lilly plans to apply for approval in the first quarter of 2027 [5]E, not peer-reviewed.

Is retatrutide legal in Finland?

Retatrutide cannot be bought legally from a pharmacy because it has no marketing authorisation in the EU [21]regulator. As of 13 Oct 2026 none of the registered phase 3 trials had a study site in Finland [6]E, not peer-reviewed.

• Medicines list. In Fimea's medicines list tirzepatide and semaglutide are medicinal substances, but retatrutide is not named in the list [24]regulator. That does not make it free to sell.
• Fimea warning, 29 Jun 2026. Fimea warned about injectable peptides sold online and on social media and marketed for uses such as weight management. According to Fimea, "for research use only" means the product is not intended for humans, and medicines should be bought only from legal pharmacies [23]regulator.
• An EU example. In August 2026 the Dutch inspectorate IGJ ordered an online shop to stop selling medicines containing retatrutide, tirzepatide and semaglutide. According to IGJ, retatrutide is an experimental drug without a marketing authorisation [22]regulator.
• Import and travel. Peptides and the law in Finland and Travelling with peptides.

This is not legal advice. Disclaimer.

Is retatrutide a doping substance?

Yes. WADA class S0 prohibits substances with no approval from any health authority for human therapeutic use, including drugs still in clinical development, and the class is prohibited at all times [9]regulator. Retatrutide is not named on the 2026 list, but without a marketing authorisation it falls within the definition of the class [9]regulator [21]regulator.

According to WADA, the status of approved GLP-1 drugs such as semaglutide and tirzepatide does not change on the 2027 list [26]regulator. That does not apply to unapproved retatrutide.

An anti-doping study developed a method meeting WADA criteria with which retatrutide could be detected in blood for about 56 days after the first injection. It was not found in urine [25]B.

Can the quality of retatrutide sold online be assessed?

Not reliably. "Retatrutide" sold online is not the drug used in the trials but an unapproved product whose content no authority has checked [7, 20]regulator.

• The amount does not match: in Australia, three products labelled as 10 mg contained 5.13, 16.5 and 19.0 mg of retatrutide, about half or almost twice the stated amount [16]D.
• Regulators: according to the FDA, products labelled "for research purposes" or "not for human consumption" have been sold directly to consumers with dosing instructions, and they are of unknown quality [20]regulator.
• Reviews: a medical journal review names retatrutide among substances on unregulated markets, with risks of contamination and inaccurate dosing [8], and a JAMA news article covered the black market for retatrutide in October 2026 [19]E, not peer-reviewed.

A certificate of analysis (COA) does not make a product a medicine or show that it is safe. More: Certificate of analysis (COA): what it tells you.

What comes next?

On 13 Oct 2026 the ClinicalTrials.gov registry listed 14 phase 3 trials of retatrutide: 5 completed, 8 active and not recruiting, and 1 recruiting [6]E, not peer-reviewed. Dates are the registry's primary completion dates: past dates are actual, future dates are estimates.

Lilly plans to apply for US approval in the first quarter of 2027 [5]E, not peer-reviewed. We know of no announced EU filing timetable. News: Peptide news.

FAQ

Read the research yourself: sources

Every source opens the original publication or the regulator's page. The level shows what the source itself reports.

1. Jastreboff AM, et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity: A Phase 2 Trial. N Engl J Med. 2023;389(6):514-526. PMID 37366315 A
2. Rosenstock J, et al. Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a phase 2 trial. Lancet. 2023;402(10401):529-544. PMID 37385280 A
3. Bajaj HS, et al. Efficacy and safety of retatrutide in people with type 2 diabetes (TRANSCEND-T2D-1): a double-blind, randomised, phase 3 trial. Lancet. 2026;407(10546):2402-2413. PMID 42250575 A
4. Giblin K, et al. Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: rationale and design of the TRIUMPH registrational clinical trials. Diabetes Obes Metab. 2026;28(1):83-93. PMID 41090431 (review)
5. Eli Lilly: press release on topline results of TRIUMPH-2 and TRIUMPH-3, 23 Jul 2026, republished by Placera. Company release, not peer-reviewed. Placera (republished release) E, not peer-reviewed
6. ClinicalTrials.gov: phase 3 studies of retatrutide (14 studies as of 13 Oct 2026, all sponsored by Eli Lilly). Registry records, not peer-reviewed. clinicaltrials.gov E, not peer-reviewed
7. FDA: Warning letter, NuScience Peptides LLC, 733652, 24 Aug 2026. fda.gov regulator
8. Moiz A, et al. Dangers of Injectable Peptides and Other Unregulated "Biohacking" Drugs. Mo Med. 2026;123(4):337-343. PMID 42757290 (review)
9. WADA: 2026 Prohibited List, class S0 Non-Approved Substances. wada-ama.org (PDF) regulator
10. Coskun T, et al. 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 Metab. 2022;34(9):1234-1247.e9. PMID 35985340 C
11. Urva S, 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. PMID 36354040 A
12. Sanyal AJ, et al. Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial. Nat Med. 2024;30(7):2037-2048. PMID 38858523 A
13. Bellido V, et al. Retatrutide in adults with obesity and type 2 diabetes (TRIUMPH-2): a double-blind, parallel-group, randomised, placebo-controlled, phase 3 trial. Lancet. 2026;408(10563):1455-1472. PMID 42810372 A
14. Jastreboff AM, et al. Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity (TRIUMPH-1). N Engl J Med. 2026 (online ahead of print 29 Sep 2026). PMID 42814954 A
15. Coskun T, et al. 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. Lancet Diabetes Endocrinol. 2025;13(8):674-684. PMID 40609566 A
16. Piatkowski T, et al. Composition and Labelling Accuracy of Products Sold as Retatrutide in Australia. Drug Alcohol Rev. 2026;45(6):e70231. Letter. PMID 42559975 D
17. Buzzi RM, Huber LC. Emerging risks of health optimisation: refractory nausea associated with peptide injections reported to contain retatrutide. BMJ Case Rep. 2026;19(10):e276106. PMID 42843917 B
18. 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. PMID 42669023 B
19. Rubin R. Unapproved GLP-1 Drugs Retatrutide and Zenagamtide Sold Online Are No Bargain. JAMA. 2026 Oct 9. Medical News article, not peer-reviewed research. PMID 42853576 E, not peer-reviewed
20. U.S. Food and Drug Administration. FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss (content current as of 1 Oct 2026). FDA regulator
21. European Medicines Agency. Medicines data: list of centrally assessed human and veterinary medicines, as of 13 Oct 2026: retatrutide not listed (tirzepatide and semaglutide are). EMA (data) regulator
22. IGJ, Health and Youth Care Inspectorate (Netherlands). Order to an online shop to stop selling medicines containing retatrutide, tirzepatide and semaglutide, news 24 Aug 2026 (penalty order 31 Aug 2026). igj.nl regulator
23. Fimea. Fimea varoittaa: älä käytä verkosta ostettuja pistettäviä peptidejä / Fimea warns: do not use injectable peptides purchased online. 29 Jun 2026. Fimea regulator
24. Finland. Lääkeluettelo (Fimea medicines list), 230/2025, annexes 1 and 1 A. Finlex regulator
25. Carneiro GRA, et al. Detection and Excretion Profile of Retatrutide in Human Plasma and Urine by LC-HRMS: Implications for Antidoping Analysis. Rapid Commun Mass Spectrom. 2026;40(23):e70179. PMID 42745421 B
26. World Anti-Doping Agency. WADA publishes 2027 Prohibited List, press release, 21 Sep 2026. WADA regulator
27. ClinicalTrials.gov. NCT07629401: Pre-approval Expanded Access of Retatrutide (LY3437943), sponsor Eli Lilly, status available, first posted 5 Jun 2026. Registry record. ClinicalTrials.gov E, not peer-reviewed
28. Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med. 2022;387(3):205-216. PMID 35658024 A
29. Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). N Engl J Med. 2021;384(11):989-1002. PMID 33567185 A
30. Marathe SJ, et al. Incretin triple agonist retatrutide (LY3437943) alleviates obesity-associated cancer progression. NPJ Metab Health Dis. 2025;3(1):10. PMID 40094000 C
31. Ding M, et al. Comparative effects of semaglutide tirzepatide and retatrutide on renal fibrosis in UUO and aged mice. iScience. 2026;29(9):117174. PMID 42630988 C
32. Petersen J, et al. Cagrilintide and retatrutide combination therapy enhances weight loss and metabolic outcomes in obese male rats. Nat Metab. 2026 (online ahead of print 15 Sep 2026). PMID 42744908 C
33. Neumann J, et al. Inotropic effects of retatrutide in isolated human atrial preparations. Naunyn Schmiedebergs Arch Pharmacol. 2026;399(1):317-327. PMID 40613938 D
34. Frías JP, et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes (SURPASS-2). N Engl J Med. 2021;385(6):503-515. PMID 34170647 A

Sources checked 12-13 Oct 2026. Piatkowski 2026 is a letter without an abstract; its figures come from the text of the letter. The figures in the Lilly release are not peer-reviewed.

Evidence levels: A = randomised human trial or meta-analysis · B = observational human study or case series · C = animal study · D = cell or laboratory study · E = not peer-reviewed · regulator = a regulator's assessment or decision, not research evidence. The marker official means official product information (summary of product characteristics or label); it is not research evidence. For a review, the level shows what kind of research the statement rests on. No level: statements that something has not been studied, reviews' interpretations, named hypotheses and the general rules in our certificate-of-analysis guide.

Content is general information about research, not medical advice. If you have symptoms, contact a healthcare professional.