Retatrutide
Retatrutide is a lab-made peptide[1]. It is also called LY3437943[1]. It acts at GIP, GLP-1 and glucagon receptors[2]. Lilly's TRIUMPH-1 report says the 12 mg group lost 28.3% of body weight at 80 weeks[8]. The placebo group lost 2.2%[8]. A peer-reviewed Phase 2 trial found a 24.2% mean loss at 48 weeks in its 12 mg group[3]. The placebo group lost 2.1%[3]. Gut events were most frequent in TRANSCEND-T2D-1[6]. Lilly still calls retatrutide an investigational drug[11]. No agency has approved it[11].
What is Retatrutide?
The Phase 2 obesity paper calls it a triple hormone receptor agonist[3]. The drug is one peptide rather than a mix of three drugs[2]. Its three targets make it a different record from semaglutide or tirzepatide.
What has been published in humans?
Human trial papers exist. They cover obesity, type 2 diabetes and liver fat. The strongest published weight result comes from a 338-person Phase 2 trial. The first published Phase 3 result comes from 537 adults with type 2 diabetes. Eli Lilly funded every paper in the table.
| Source | People and design | Measured result | Limit and funder | Checked |
|---|---|---|---|---|
| [3] | The double-blind trial enrolled 338 adults with obesity or overweight plus a weight-related condition[3]. | At 48 weeks, mean weight change was -8.7% at 1 mg, -17.1% in the combined 4 mg groups, -22.8% in the combined 8 mg groups, -24.2% at 12 mg and -2.1% with placebo. | The abstract reports no confidence intervals for these values. Funded by Eli Lilly. | 2026-09-02 |
| [4] | The trial randomized 281 adults and included 275 in the efficacy analysis[4]. | At 36 weeks, mean weight change was -16.94% at 12 mg, versus -3.00% with placebo and -2.02% with dulaglutide. | The abstract reports standard errors rather than confidence intervals for these values. Funded by Eli Lilly. | 2026-09-02 |
| [5] | The substudy randomized 98 adults from the obesity trial who had at least 10% liver fat[5]. | At 24 weeks, mean relative liver-fat change was -42.9%, -57.0%, -81.4% and -82.4% across the 1, 4, 8 and 12 mg groups, versus +0.3% with placebo. | Every active comparison was P<0.001. Funded by Eli Lilly. | 2026-09-02 |
| [6] | The 40-week trial randomized 537 adults with type 2 diabetes not adequately controlled by diet and exercise[6]. | Mean weight change was -11.5% at 4 mg, -13.9% at 9 mg and -15.3% at 12 mg, versus -2.6% with placebo. | The abstract reports standard errors. Funded by Eli Lilly. | 2026-09-02 |
The published TRIUMPH design paper describes four Phase 3 studies with more than 5,800 participants[7]. TRIUMPH-1 and TRIUMPH-2 are basket trials with nested sleep-apnoea or knee-pain protocols. TRIUMPH-3 studies people with severe obesity and cardiovascular disease. TRIUMPH-4 is a stand-alone knee osteoarthritis trial. This design paper reports plans, not outcomes. Eli Lilly funded it.
What have the current Phase 3 sponsor toplines reported?
Lilly has released topline results for three TRIUMPH weight-management trials. These results come from the sponsor. They are not substitutes for peer-reviewed full reports.
| Source | Population | Sponsor-reported result | Limit | Checked |
|---|---|---|---|---|
| [8] | Lilly says 2,339 adults were randomized without diabetes. ClinicalTrials.gov lists 2,335 actual enrollment[10]. | Under the efficacy estimand at 80 weeks, mean weight change was -19.0% at 4 mg, -25.9% at 9 mg, -28.3% at 12 mg and -2.2% with placebo[8]. | Lilly reports the result and gives no confidence intervals. | 2026-09-02 |
| [9] | Lilly reports 1,152 adults with type 2 diabetes and obesity or overweight. | Under the efficacy estimand at 80 weeks, mean weight change was -12.7% at 4 mg, -19.1% at 9 mg, -20.8% at 12 mg and -4.0% with placebo[9]. | Lilly reports the result. Detailed peer-reviewed results were pending in the release. | 2026-09-02 |
| [9] | Lilly reports 1,949 adults with severe obesity and established cardiovascular disease. | Under the efficacy estimand at 80 weeks, mean weight change was -21.6% at 9 mg, -22.6% at 12 mg and -3.2% with placebo[9]. | Lilly reports the result. Detailed peer-reviewed results were pending in the release. | 2026-09-02 |
How does Retatrutide compare with tirzepatide?
TRIUMPH-5 is a direct Phase 3 comparison. Its registry record names retatrutide and tirzepatide as the two active drugs[16]. It lists an estimated 800 adults with obesity. The study is active and no longer recruiting. It posts no results. Primary completion is estimated for December 2026.
Mounjaro contains tirzepatide[15]. Results from separate retatrutide and tirzepatide trials are not a head-to-head answer. This page does not rank one drug as better or safer.
What side effects and safety findings were recorded?
The Phase 2 obesity trial says gut events were most common[3]. Most were mild or moderate. The rate rose with the dose. Heart rate also rose with the dose. It peaked at week 24 and then fell.
In the Phase 2 diabetes trial, gut events occurred in 67 of 190 people given retatrutide[4]. They occurred in 6 of 45 people given placebo. They occurred in 16 of 46 people given dulaglutide. The trial reported no severe low blood sugar. It reported no deaths. Eli Lilly funded the trial.
TRANSCEND-T2D-1 says gut events were most frequent[6]. Most were mild or moderate. They eased over time. Adverse events caused 2% to 5% of active participants to stop, versus 0% with placebo. The trial reported no severe low blood sugar. Two deaths occurred in the 4 mg group. The authors assessed both as unrelated to the study drug. Eli Lilly funded the trial.
Lilly's TRIUMPH-1 release reports the following 80-week rates. They are sponsor toplines rather than a peer-reviewed full safety table.
| Source | Event | 4 mg | 9 mg | 12 mg | Placebo |
|---|---|---|---|---|---|
| [8] | Nausea | 28.6% | 38.4% | 42.4% | 14.8% |
| [8] | Diarrhoea | 25.2% | 34.1% | 32.0% | 13.5% |
| [8] | Constipation | 23.8% | 25.9% | 26.1% | 10.9% |
| [8] | Vomiting | 10.6% | 22.8% | 25.3% | 4.8% |
| [8] | Dysesthesia | 5.1% | 12.3% | 12.5% | 0.9% |
| [8] | Stopped treatment because of an adverse event | 4.1% | 6.9% | 11.3% | 4.9% |
Lilly says dysesthesia was generally mild to moderate[8]. The release says most cases resolved during treatment. Most affected participants continued treatment.
What dosage information do sources report for Retatrutide?
These are source reports. They are not site advice. The studies tested different weekly amounts in defined populations. The user-report row records what one poster wrote. No row turns an amount into a plan.
| Source | Reported amount | Source type | What that means here | Checked |
|---|---|---|---|---|
| [3] | The Phase 2 obesity trial studied 1 mg, 4 mg, 8 mg and 12 mg once weekly for 48 weeks[3]. | Randomized human trial | The study enrolled 338 adults with obesity or overweight plus a weight-related condition. | 2026-09-02 |
| [4] | The Phase 2 diabetes trial studied 0.5 mg, 4 mg, 8 mg and 12 mg once weekly for 36 weeks[4]. | Randomized human trial | The study randomized 281 adults with type 2 diabetes. | 2026-09-02 |
| [6] | TRANSCEND-T2D-1 studied 4 mg, 9 mg and 12 mg once weekly for 40 weeks[6]. | Randomized Phase 3 human trial | The study randomized 537 adults with type 2 diabetes. | 2026-09-02 |
| [10] | Lilly's TRIUMPH-1 topline reports target groups of 4 mg, 9 mg and 12 mg over 80 weeks[8]. | Sponsor-reported Phase 3 trial | The release reports 2,339 randomized; the registry reports 2,335 actual enrollment. | 2026-09-02 |
| [14] | One poster reported 2 mg during her third week and later reported 1 mg[14]. | Self-reported, self-selected public account | No laboratory result in the thread confirms the product identity or amount. | 2026-09-02 |
No approved drug source gives a retatrutide amount[11]. No approved retatrutide drug exists[11]. The amounts above belong to research arms only.
What do animal and laboratory studies add?
The discovery paper tested cells, mice and a first human study. In test systems, LY3437943 acted at the glucagon, GIP and GLP-1 receptors[2]. In obese mice, it lowered body weight. It also improved blood sugar control. The authors linked part of the mouse weight change to higher energy use through the glucagon receptor. The mouse result does not give a human effect size.
The same paper reports that weight loss lasted through day 43 after one amount in its Phase 1 study[2]. Its abstract says the safety pattern was like other incretins. Eli Lilly funded the paper.
What has direct vial or product testing found?
Direct tests ask if a sample matched its label. They say nothing about an untested vial. They also do not measure an effect in a person.
| Source | Direct retatrutide finding | Limit | Funder note | Checked |
|---|---|---|---|---|
| [13] | The authors reported 59 identity failures among reports labelled retatrutide[13]. | The paper's text does not give the identity-failure denominator beside that count. | No external funding and no declared conflicts. | 2026-09-02 |
| [13] | Retatrutide had the highest dual-pass rate among 14 peptides under the study's 90-110% amount and at least 98% purity model, at 67.8%[13]. | The study thresholds are analytic models, not regulatory approval. | No external funding and no declared conflicts. | 2026-09-02 |
| [13] | Under the tighter 95-105% amount and at least 99.5% purity model, retatrutide again ranked highest at 47.0%[13]. | The manuscript has not been peer reviewed. | No external funding and no declared conflicts. | 2026-09-02 |
| [13] | Figure 5 labels the retatrutide amount-and-purity analysis N=507[13]. | The dataset came from voluntary submissions and was not a random market survey. | No external funding and no declared conflicts. | 2026-09-02 |
The full set had 6,487 reports across 14 peptides[13]. The authors kept 6,285 reports for amount and purity tests. A smaller set had 243 endotoxin results. The text gives no endotoxin result for retatrutide alone.
The vial-testing guide keeps identity, amount, purity and endotoxin apart. The sterility guide covers what a purity test cannot show.
What do user reports add?
User reports are self-reported and self-selected. This public Reddit thread carries no disclosed sponsor or payment. No laboratory report in the thread confirms the claimed product identity. The whole thread remains linked so the account can be read in context.
PositionVast9155, who identified herself as 31 and female, described weight change, appetite change and gastrointestinal effects during her third week[14]:
So I’m going on my third week using Reta 2mg and I’m down just over 6lbs but I’ve had some wild side effects. The first week I was fine, appetite was suppressed but I could still eat, had some gas/sulphur burps after I ate eggs one night and that never went away. Week 2 I can barely look at food, the thought or idea of it is so unappealing and sometimes makes me sick to think about it. I can hardly take more than a few bites of something before I get nauseous.
I also have crazy diarrhea (tmi I know) and gas/sulphur burps and I can feel a lot of gurgling in my abdomen/intestines?.
In a later reply, the same user wrote:
I notice at 1mg I have energy and not food noise/hunger but can still eat and have no other sides.
Months later, she wrote:
Yes they did. I lowered my dose to 1mg and waited a month before upping it again. After about 2-4mo the all symptoms were gone
These posts describe one person's account. They are not a count of what most users experience.
What is the current evidence status, and what is the regulatory status?
Trial strength, approval status and vial tests answer separate questions. A strong trial does not identify another vial. Lack of approval does not erase a trial result.
| Question | Current answer | Source and limit | Checked |
|---|---|---|---|
| Evidence tier | The current A/B definitions do not fit this record cleanly. Published Phase 3 human data exists[6], but retatrutide has no regulatory approval[11]. | Tier A currently requires approval plus Phase 3 data. Tier B describes human evidence that is small, short, early phase or for another indication. This is a schema uncertainty, not an evidence absence. | 2026-09-02 |
| Published human evidence | Randomized Phase 2 and Phase 3 papers report weight, HbA1c, liver-fat and safety outcomes[6]. | Every cited trial paper discloses Eli Lilly funding. | 2026-09-02 |
| Current regulatory status | Lilly states that retatrutide is investigational and is not approved by any regulatory agency[11]. | This is the developer's current status statement. It is not an independent trial result. | 2026-09-02 |
| EU central register | Retatrutide did not appear in the EMA centrally authorised medicines workbook checked for this page[12]. | The workbook covers the central EU route, not every national medicine route. | 2026-09-02 |
| Planned application | Lilly says it plans to submit a US Biologics License Application in the first quarter of 2027[9]. | A planned application is not an approval or a public sale date. | 2026-09-02 |
| Product presentation | The cited human trials studied once-weekly subcutaneous injections[3]. | No approved retatrutide pen, tablet or vial exists in the cited status source. Trial method is not a product instruction. | 2026-09-02 |
| Direct vial evidence | The 2026 preprint reports retatrutide identity failures and amount-and-purity results[13]. | The submissions were voluntary and self-selected. The paper has not been peer reviewed. | 2026-09-02 |
See also
- Full retatrutide guide - read the same-compound side-effects guide and its trial tables.
- Weight-loss research hub - compare separate retatrutide, tirzepatide and semaglutide trial results without treating them as head-to-head.
- Counterfeit GLP-1 evidence - read direct testing and case evidence for products sold under GLP-1 medicine labels.
- Vial-testing guide - separate identity, amount, purity, endotoxin and sterility findings.
- Sterility guide - separate chemical purity from sterile-use evidence.
FAQ
How long does retatrutide take to work?
The Phase 2 obesity trial checked weight at weeks 24 and 48[3]. The first study saw weight loss last through day 43 after one amount[2]. Neither paper gives one first-effect day for all people.
Is retatrutide available to the public?
No approved retatrutide drug is now on sale. Lilly says the drug is still in trials[11]. No agency has approved it. Lilly plans a US filing in early 2027[9].
Does retatrutide come as a pen or tablet?
No approved retatrutide pen or tablet exists in the status source[11]. The human trials used shots under the skin. That is a trial method, not an instruction.
What side effects were most common with retatrutide?
Gut events were most frequent in the published trials[6]. Lilly lists nausea, diarrhoea, constipation and vomiting among the most common TRIUMPH-1 events[8]. The safety table gives each group rate.
References
- ↑ a b c d e f g NCATS GSRS. Retatrutide record. UNII NOP2Y096GV. Names. Codes. Sodium record. Used for names and IDs. Used for the salt record. Checked 2026-09-02.
- ↑ a b c d e f Coskun T et al. LY3437943 from discovery to human study. Cell Metabolism, 2022. PMID 35985340. DOI 10.1016/j.cmet.2022.07.013. Used for the three targets. Used for mouse and Phase 1 findings. Funded by Eli Lilly. Checked 2026-09-02.
- ↑ a b c d e f g h i j k Jastreboff AM et al. Retatrutide for obesity. New England Journal of Medicine, 2023. PMID 37366315. NCT04881760. Used for the trial plan and who took part. Used for amounts, weight, gut events and pulse. Funded by Eli Lilly. Checked 2026-09-02.
- ↑ a b c d e Rosenstock J et al. Retatrutide for type 2 diabetes. The Lancet, 2023. PMID 37385280. NCT04867785. DOI 10.1016/S0140-6736(23)01053-X. Used for the trial plan and who took part. Used for amounts, weight, blood sugar and harms. Funded by Eli Lilly. Checked 2026-09-02.
- ↑ a b Sanyal AJ et al. Retatrutide and liver fat. Nature Medicine, 2024. PMID 38858523. Used for the 98-person study and liver-fat results. Funded by Eli Lilly. Checked 2026-09-02.
- ↑ a b c d e f g h i j Bajaj HS et al. TRANSCEND-T2D-1 Phase 3 trial. The Lancet, 2026. PMID 42250575. NCT06354660. DOI 10.1016/S0140-6736(26)00967-0. Used for the trial plan and who took part. Used for amounts, weight, blood sugar and harms. Funded by Eli Lilly. Checked 2026-09-02.
- ↑ Giblin K et al. TRIUMPH trial design. Diabetes, Obesity and Metabolism, 2026. PMID 41090431. Used for programme size and basket design. Used for trial groups. This paper reports plans, not results. Funded by Eli Lilly. Checked 2026-09-02.
- ↑ a b c d e f g h i j k l m Eli Lilly and Company. TRIUMPH-1 Phase 3 report. Sponsor release, 21 May 2026. Used for sponsor weight and safety results. Used for trial amounts and count. The weight table has no confidence bounds. Checked 2026-09-02.
- ↑ a b c d e f Eli Lilly and Company. TRIUMPH-2 and TRIUMPH-3 reports. Sponsor release, 23 July 2026. Used for sponsor weight and safety results. Used for study counts and planned US filing. Full peer-reviewed results were pending. Checked 2026-09-02.
- ↑ a b Eli Lilly and Company. TRIUMPH-1 trial record. ClinicalTrials.gov. NCT05929066. Used for actual enrollment and sponsor. Used for status and the lack of posted results. Checked 2026-09-02.
- ↑ a b c d e f g h i Eli Lilly and Company. What to know about retatrutide. Updated July 2026. Used for trial status and approval absence. Used for the lack of public access. This is the drug maker's statement. Checked 2026-09-02.
- ↑ European Medicines Agency. Medicines report. Used for the central EU search. The file does not cover all state routes. Checked 2026-09-02.
- ↑ a b c d e f g h i j Mendias CL, Awan TM. Tests of peptides sold to consumers. Preprints.org, 2026. DOI 10.20944/preprints202604.1748.v1. Used for counts and retatrutide test results. Used for study limits and review status. No outside funding. No declared conflicts. Checked 2026-09-02.
- ↑ a b c PositionVast9155. Can't eat?. r/Retatrutide, 2025. Used for one open self-report. Used for weight, hunger, gut effects and amounts. No payment is disclosed. No lab report is shown. Checked 2026-09-02.
- ↑ European Medicines Agency. Mounjaro overview. EMA. Used only to name tirzepatide as the active drug in Mounjaro. Checked 2026-09-02.
- ↑ Eli Lilly and Company. TRIUMPH-5 head-to-head trial record. ClinicalTrials.gov. NCT06662383. Used for the study drugs, planned count, status, result absence and estimated end date. Sponsor listed as Eli Lilly. Checked 2026-09-02.