Retatrutide
PeptideThe community rates retatrutide very positively based on impressive subjective weight loss figures [c1, c2, c3], while the medical score is limited by the absence of complete Phase 3 publications, a pending long-term safety profile, and incomplete regulatory approval processes [s1, s6, s7].
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TL;DR
Retatrutid is the most potent weight-loss candidate currently in clinical development: Phase 2 data show −24.2% body weight at 12 mg, with Phase 3 topline results reaching −28.7% — figures that clearly surpass semaglutide and tirzepatide. As a triple GLP-1/GIP/glucagon receptor agonist with a ~6-day half-life, it is administered once weekly by subcutaneous injection; FDA approval is pending, and EMA submission is not expected before Phase 3 completion. Community enthusiasm is high but largely uncritical — grey-market sourcing means unknown purity, and an emerging arrhythmia safety signal from Phase 3 is barely on most users' radar. Self-experimentation without medical supervision carries real risk with this class of compound.
Description
Retatrutide is an experimental triple GLP-1/GIP/glucagon receptor agonist by Eli Lilly in Phase 3 clinical development for obesity [s1, s2].
Retatrutide (LY3437943) is a novel, once-weekly subcutaneously administered peptide agent that simultaneously activates three hormone receptors: the glucagon-like peptide-1 receptor (GLP-1R), the glucose-dependent insulinotropic polypeptide receptor (GIPR), and the glucagon receptor (GCGR) [s1, s2]. It is being developed by pharmaceutical company Eli Lilly under the TRIUMPH Phase 3 program [s6, s7]. In a Phase 2 RCT (n=338, 48 weeks), mean weight reductions of 24.2% from baseline were documented at the highest dose (12 mg/week) — the highest value observed in a clinical obesity trial at that time [s1, s3]. In the Phase 3 TRIUMPH-4 study, mean weight loss of up to 28.7% (average 71.2 lbs) was reported at the two highest dose levels, along with significant relief of gonarthrosis pain in obese patients [s6]. A Phase 2a substudy in metabolic dysfunction-associated steatotic liver disease (MASLD/NASH) also showed promising results regarding hepatic fat reduction [s5]. Cardiovascular endpoint studies (TRIUMPH-CVOT, approx. 10,000 participants) are still ongoing [s4]. As of April/May 2026, Eli Lilly has not yet submitted marketing authorization applications to the FDA or EMA. An NDA submission is expected by late 2026 or early 2027; possible market approval at the earliest in 2027–2028 [s7, s8]. Despite the lack of approval, retatrutide is already prevalent in biohacker and self-experimentation circles and is sourced through unregulated online vendors [c1, c2, c3].
Legal Status (DE)
{'ema_maa_status': 'As of May 2026: No active EMA Marketing Authorisation Application (MAA) for retatrutide identifiable. Only an EMA Paediatric Investigation Plan (PIP) is documented. The Phase 3 TRIUMPH regulatory pathway is primarily pursued via the FDA; an EMA submission is expected following completion of Phase 3 studies. Source: available sources (s8 PIP); no EPAR entry found. ', 'paragraph_73_amg_source_ids': ['s9']}
Mechanism of Action
{'half_life_note': 'Retatrutide has a half-life of approximately 6 days (dose-proportional pharmacokinetics), enabling once-weekly subcutaneous administration. Supported by: NEJM Phase 2 paper (s1, NEJMoa2301972), Nature Medicine MASLD study (s5, DOI 10.1038/s41591-024-03018-2), and Phase 1 study Coskun et al. (s16, DOI 10.1016/j.cmet.2022.07.013). ', 'half_life_source_ids': ['s1', 's5', 's16']}
Dosing
Allgemein
- Dose
- Frequency
- 1× täglich
- Route
- oral
- With food
- optional
Allgemein
- Dose
- Frequency
- 1× täglich
- Route
- oral
- With food
- optional
Calculate reconstitution, plan dosing, look up injection technique
Side Effects
| Side Effect | Frequency | Severity |
|---|---|---|
| Übelkeit (Nausea) Most common side effect; in the phase 2 study occurring in up to 60% of participants in the 12 mg group, predominantly mild to moderate, particularly during dose titration [s1, s13]. | häufig | moderat |
| Durchfall (Diarrhoe) Gastrointestinal adverse effect, frequently reported in phase 2 and phase 3 studies, dose-dependent [s1, s6]. | häufig | leicht |
| Erbrechen Occurred more frequently than placebo in the phase 2 study, particularly in higher dose groups [s1]. | gelegentlich | moderat |
| Verstopfung (Obstipation) Known GLP-1 class adverse effect due to delayed gastric emptying, also reported with retatrutide [s1, s14]. | gelegentlich | leicht |
| Herzfrequenzanstieg (dosisabhängig) Clinical trials have reported dose-dependent increases in heart rate and isolated cases of cardiac arrhythmias [s13, s14]. | gelegentlich | moderat |
| Dysästhesie (Hautbrennen, Kribbeln, 'Sonnenbrand-Gefühl') Specific adverse effect signal for retatrutide; reported by community users and in clinical data; mechanism unclear [c1, s13]. | gelegentlich | leicht |
| Müdigkeit (Fatigue) Reported by users in community reports; classified as non-serious in clinical trials [c2, s1]. | gelegentlich | leicht |
| Reaktionen an der Injektionsstelle Local redness, swelling, or pain at the injection site; classic adverse effect of subcutaneous peptide injections [s1]. | gelegentlich | leicht |
| Kardiale Arrhythmien (neues Sicherheitssignal Phase 3) A new safety signal for cardiac arrhythmias was reported in Phase 3 results (TRIUMPH-4); exact incidence not yet fully published [s6]. | selten | schwer |
| Gallenblasenerkrankungen (Cholelithiasis) Class effect of GLP-1 agonists due to rapid weight loss; increased gallstone risk is theoretical and established with related compounds [s1, s14]. | selten | moderat |
| Muskelschwund (Sarkopenie) bei schnellem Gewichtsverlust With very rapid weight loss (>24% in 48 weeks), loss of muscle mass is possible; raised as a concern in community reports and expert discussions [c4, s14]. | theoretisch | moderat |
Contraindications
Class warning for all GLP-1 agonists based on animal studies (C-cell tumors); also assumed to be a potential contraindication for retatrutide [s1, s14].
Contraindication analogous to other GLP-1 agonists; increased risk of medullary thyroid carcinoma [s1, s14].
No safety data available for pregnancy/lactation; experimental compound without regulatory approval [s1, s7].
Increased pancreatitis risk is a class effect of GLP-1 agonists; caution in patients with a history of pancreatitis [s1, s14].
Due to the new arrhythmia safety signal in TRIUMPH-4, particular caution is warranted in patients with pre-existing cardiac arrhythmias [s6].
Safety data in severe renal insufficiency are lacking; caution analogous to related compounds is warranted [s1, s14].
No safety or efficacy data available for minors; the EMA has agreed on a paediatric investigation plan (PIP), but no results are available [s8].
Interactions
Synergistic
Combination not studied; theoretically additive GI toxicity and hypoglycemia risk; combination not advisable [s14].
Berberine activates AMPK and improves insulin sensitivity via mechanisms complementary to retatrutide's GLP-1/GIP action. The combination may additively improve glucose control and lipid metabolism. No clinical studies on the direct combination are currently available.
Myo-inositol improves insulin sensitivity, thereby complementing the insulinotropic effect of retatrutide. Both substances may synergistically support glucose metabolism. Clinical data on the combination are not yet available.
During retatrutide-induced caloric restriction and weight loss, BCAA/EAA supplementation may reduce muscle mass loss. Preliminary evidence from GLP-1 RA studies suggests better preservation of lean mass. Resistance training augments this effect.
Retatrutide can cause gastrointestinal side effects such as nausea and delayed gastric emptying. BPC-157 promotes healing and regeneration of the intestinal mucosa and may alleviate these GI complaints. The combination has not yet been clinically investigated.
Ipamorelin stimulates growth hormone release and may counteract muscle mass loss resulting from the caloric deficit induced by retatrutide. The combination may synergistically improve body composition, fat loss, and recovery. Clinical data on the direct combination are not yet available.
CJC-1295 stimulates growth hormone release and complements the fat-reducing effect of retatrutide. The combination may support lean mass preservation during retatrutide-induced weight loss. Currently supported only by mechanistic rationale; no clinical studies available.
Caution
Increased hypoglycemia risk due to additive insulinotropic effects of GLP-1/GIP agonism; dose adjustment of other antidiabetic agents required [s1, s14].
Delayed gastric emptying via GLP-1 action may affect absorption of oral medications; a time interval between administrations is recommended [s14].
In light of the new arrhythmia safety signal from TRIUMPH-4, particular caution is warranted with concurrent use of drugs with cardiac effects [s6].
Tirzepatide is a GLP-1/GIP dual agonist sharing two of the three receptor targets of retatrutide. Concurrent use results in direct receptor competition and substantially increases the risk of severe gastrointestinal side effects and hypoglycemia.
Semaglutide is a GLP-1 receptor agonist sharing one of the three receptor targets of retatrutide. The combination is contraindicated, as it leads to receptor competition and a markedly increased risk of gastrointestinal complications and hypoglycemia.
Metformin and retatrutide both lower blood glucose; the combination may increase the risk of hypoglycemia, particularly with inadequate food intake. Additionally, gastrointestinal side effects (nausea, diarrhea) may be additive. Dose adjustment and close monitoring are required.
Retatrutide may affect steroid hormone metabolism via glucagon receptor agonism and altered insulin sensitivity. DHEA as a hormonal precursor could exhibit unpredictable endocrine effects during concurrent severe caloric restriction. Close hormone monitoring is recommended.
Studies
Tier A — High Evidence
Tier B — Moderate Evidence
Effect Size: Relative liver fat reduction at 24 weeks: −42.9% (1 mg), −57.0% (4 mg), −81.4% (8 mg), −82.4% (12 mg) vs. +0.3% (placebo). At 48 weeks: −86% (12 mg). Normalization of liver fat (<5%) in 86% of participants (12 mg, week 24). All doses p<0.001 vs. placebo.
Community Evidence
Top reported benefits
- Significant and rapid weight reduction (reported: −20 to −30 kg in 3–6 months)
- Strong appetite suppression from the first week onwards
- Sensation of 'fat loss' without intensive exercise (glucagon component)
- Superiority over tirzepatide and semaglutide in self-experimentation
- Improvement in metabolic lab values (blood glucose, blood lipids)
Top reported issues
- Nausea and vomiting, particularly during the titration phase
- Dysesthesia: burning or tingling skin sensation (specific to retatrutide)
- Unreliable quality from unregulated suppliers
- Fatigue and exhaustion in the early weeks
- High costs when obtained from unregulated sources
Retatrutide is not approved; procurement through unregulated online vendors carries risks from unknown purity and dosing inaccuracy [c1, c4]. A new arrhythmia safety signal from Phase 3 studies is not yet widely known in the community [s6]. The risk of muscle mass loss with rapid weight loss is increasingly being discussed [c4]. Self-experimentation without medical supervision is clearly discouraged by medical experts [c5].
Scientific Sources
- Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial
Jastreboff AM, Aronne LJ, Ahmad NN, et al. (2023). New England Journal of MedicineAPMID:37352106DOI - Retatrutide Half-Life: Duration, Dosage, Clearance Time, And Comparison
Swolverine Editorial (2024). swolverine.comDLink - Retatrutide Dosing Guide: 2mg–12mg Protocol + Calculator
GLP3 Planner Editorial (2024). glp3planner.comDLink - Retatrutide Dose Escalation Chart: 1mg to 12mg
Lola Health Editorial (2024). lolahealth.comDLink - Retatrutide Side Effects: Clinical Trial Data, Risks And Safety Profile
Swolverine Editorial (2024). swolverine.comDLink - Retatrutide: Neues Medikament zur Gewichtsreduktion
ZAVA Medizinisches Team (2024). zavamed.comDLink - Is retatrutide (LY3437943), a GLP-1, GIP, and glucagon receptor agonist, the next big step in treating metabolic disease?
Newsome PN, Ambery P (2023). Cell MetabolismBPMID:37086147DOI - LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: from discovery to clinical proof of concept
Coskun T, Urva S, Roell WC et al. (2022). Cell MetabolismADOI - Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: Rationale and design of the TRIUMPH registrational clinical trials
Giblin K, Kaplan LM, Somers VK, Le Roux CW, Hunter DJ, Wu Q, Lalonde A, Ahmad N, Bethel MA (2026). Diabetes, Obesity and MetabolismADOI - 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
Frías JP, Álvarez-Villalobos NA, Bhatt DL et al. (2023). The LancetADOI - LY3437943, a novel triple GIP, GLP-1, and glucagon receptor agonist for glycemic control and weight loss
Coskun T, Urva S, Roell WC, et al. (2022). Cell MetabolismCPMID:36354040DOI - Efficacy and safety of retatrutide, a novel GLP-1, GIP and glucagon receptor agonist — systematic review and meta-analysis
Hinnen D, Alfaris N, Bays HE, et al. (2025). PMC / FrontiersALink - Retatrutide for the treatment of obesity, obstructive sleep apnea, and related comorbidities
Rubino DM, Greenway FL, Khalid U, et al. (2025). PubMed / Expert OpinionBPMID:41090431 - Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial
Loomba R, Hartman ML, Lawitz EJ, et al. (2024). Nature MedicineADOI - Lilly's triple agonist, retatrutide, delivered weight loss of up to an average of 71.2 lbs along with substantial relief from osteoarthritis pain in first successful Phase 3 trial (TRIUMPH-4)
Eli Lilly and Company (2025). Eli Lilly Investor Relations Press ReleaseBLink - Retatrutide FDA: NOT Approved Yet (NDA Q4 2026, Approval 2027)
RetaWeightLoss Editorial (2026). retaweightloss.comDLink - EMA paediatric investigation plan EMEA-003258-PIP02-23 for retatrutide
European Medicines Agency (2024). European Medicines AgencyALink - Rechtlicher Status von Retatrutide 2025: Noch in der klinischen Erprobung
Retatruti.de Redaktion (2025). retatruti.deDLink
Community Sources
Storage
Unopened
Store at 2–8 °C under refrigeration; do not freeze. Specifications are based on clinical study protocols; no product information available as the product is not approved.
Opened
After opening the injection vial/prefilled syringe, use within 28 days at 2–8 °C or up to 7 days at room temperature per clinical protocol (data from study context; may vary by formulation).
Notes
As retatrutide is not an approved product, no official product information sheet exists. Storage specifications are derived from clinical study protocols [s1].