At a glance
Effects
- Body weight reduction: Phase 2 trials showed up to 24.2% mean body weight loss after 48 weeks at the 12 mg dose; 68-week Phase 3 data report up to 28.7% loss and an average of ~71.2 lbs in weight-loss-specific trials [7][8].
- Blood glucose / HbA1c improvement: In a Phase 2 T2D trial, HbA1c improved by 1.3–2.0% across 4–12 mg dose groups; 82% of higher-dose participants reached HbA1c ≤6.5% [9].
- Liver fat reduction: Phase 2a data (Nature Medicine 2024) showed up to 82% reduction in liver fat, the largest drug-induced reduction recorded for MASLD/MASH [5].
- Cardiometabolic markers: Improvements in triglycerides, blood pressure, waist circumference, and fasting plasma glucose (mean −23.51 mg/dL) were observed across randomised controlled trials [10].
- Appetite suppression: GLP-1R and GIPR agonism together reduce appetite, slow gastric emptying, and increase feelings of fullness, supporting sustained caloric restriction [3].
Triple GLP-1/GIP/glucagon receptor agonist (incretin-based peptide)
Investigational — Phase 3 (TRIUMPH); not FDA/MHRA approved as of 2026
~6 days (supports once-weekly dosing)
Subcutaneous injection (once weekly)
Eli Lilly (LY3437943)
About Retatrutide
Every point here is drawn from public medical and harm-reduction sources. A bracketed number after a claim — like [1]— is a reference: tap it to open the exact source it's based on (numbered list at the bottom). It is not a rating or score. Educational information, not medical advice.
Product specifics
- Est. delivery
- 3–7 business days · EU tracked
Product details as stated by the vendor (claims, not independently verified). Delivery is our standard EU estimate.
What it is
Retatrutide (LY3437943) is an investigational synthetic peptide and triple hormone-receptor agonist developed by Eli Lilly, targeting the GLP-1, GIP, and glucagon receptors simultaneously [1][2]. It is being studied primarily for the treatment of obesity and type 2 diabetes, and is not yet approved by any regulatory authority for prescription use [6].
How it works
Retatrutide simultaneously activates three incretin/metabolic receptors [1][2]: (1) GLP-1R — enhances glucose-stimulated insulin secretion, slows gastric emptying, and promotes satiety [3]; (2) GIPR — potentiates postprandial insulin response and may synergistically amplify weight-loss effects [4]; (3) GCGR — drives increased hepatic energy expenditure and fat oxidation, raising resting energy burn [5]. The combined effect is a simultaneous reduction in caloric intake (via appetite suppression) and increase in energy expenditure (via glucagon activity), producing a metabolic profile that in Phase 2 data exceeded all previously studied compounds of its class [3][7]. Structurally, it is a single peptide coupled to a fatty diacid chain (acylation) which extends its half-life to approximately six days, supporting once-weekly subcutaneous dosing [1].
Risks & side effects
Most important: The most clinically significant risk is a dose-dependent increase in heart rate of approximately 5–10 beats per minute, peaking around week 24, with additional signals of cardiac arrhythmia (including one case of QT prolongation at 12 mg) observed in Phase 2 data [11][12]. Combined with the class-level risk of acute pancreatitis (reported in ~0.3% of trial participants) and the theoretical thyroid C-cell tumour warning carried by all GLP-1 receptor agonists, individuals with pre-existing cardiovascular disease, a history of pancreatitis, or a personal/family history of medullary thyroid carcinoma or MEN2 should not use this substance [13][12].
Common
- Nausea — reported in 14–60% of participants across dose groups; most intense during dose escalation, typically transient [8]
- Vomiting — dose-dependent, 3–26% across 1–12 mg dose range [8]
- Diarrhoea and constipation — due to slowed gastric motility [13]
- Elevated resting heart rate — ~5–10 bpm increase, dose-dependent, peaking at ~week 24 [11]
- Dysaesthesia / skin sensory changes — mild, not severe; did not lead to discontinuation in trials [14]
- Injection-site reactions — consistent with subcutaneous peptide administration [12]
- A substantial share of the weight lost is lean mass, not fat — trial data put it at roughly a quarter to a third of total weight lost without resistance training and adequate protein.[1]Keep resistance training and protein intake high throughout, and avoid aggressive dose escalation.[1]
Serious
- Cardiac arrhythmia — numerically higher incidence in retatrutide groups vs placebo; one case of QT prolongation at 12 mg [14]
- Acute pancreatitis — one serious case at 12 mg in Phase 2; ~0.3% reported incidence in trials [13][12]
- Gallbladder disease — ~0.5–1% of patients; largely attributed to rapid weight loss [13]
- Severe gastrointestinal intolerance — 6–16% of participants discontinued in trials primarily due to GI adverse events [15]
- Hypoglycaemia — increased risk when combined with insulin or sulfonylureas [16]
Rare
- Medullary thyroid carcinoma — class-level preclinical (rodent) warning; no cases of MTC or C-cell hyperplasia confirmed in human trials to date [12][17]
- QT interval prolongation — one case at 12 mg in Phase 2 trials [14]
- Acute kidney injury — theoretical risk via dehydration from GI effects; severe renal impairment (eGFR <30) is a contraindication [18]
Safety & harm reduction
- Personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia type 2 (MEN2) [17]
- History of pancreatitis or active pancreatic disease [19]
- Severe renal impairment (eGFR <30 mL/min/1.73m²) [18]
- Pregnancy or lactation [19]
- Known hypersensitivity to retatrutide or any component [19]
- Unstable angina or recent myocardial infarction (within 6 months) [19]
- Under 18 or over 80 years of age (excluded from all trials to date) [19]
- Resting heart rate and ECG — especially in patients with pre-existing cardiovascular disease, given dose-dependent heart rate elevation [11]
- Pancreatic enzymes (amylase/lipase) — monitor for pancreatitis, particularly at higher doses [12]
- Liver enzymes (ALT/AST) — baseline and periodic monitoring [15]
- Kidney function (eGFR, creatinine) — particularly in patients with borderline renal function or significant GI fluid losses [18]
- Blood glucose and HbA1c — especially in patients on concurrent insulin or sulfonylureas due to hypoglycaemia risk [16]
- Thyroid function and neck examination — thyroid family history should be documented at baseline [19]
- Insulin and sulfonylureas — increased hypoglycaemia risk; dose reduction of the concomitant agent may be required [16]
- Oral medications — delayed gastric emptying may reduce absorption rate of orally administered drugs; consider timing adjustments [19]
- Warfarin / anticoagulants — potential for altered absorption; INR monitoring advised [19]
- Drug interactions not fully characterised — as an unapproved investigational agent, the complete interaction profile remains unknown [14]
- Stepwise dose titration is mandatory to minimise gastrointestinal adverse events — starting at 2 mg is better tolerated than 4 mg per Phase 2 data [8]
- Refrigerate at 2–8°C (36–46°F); do not freeze [20]
- Maintain consistent weekly dosing schedule to sustain pharmacokinetic steady state [20]
- Lifestyle intervention (diet and physical activity) should accompany pharmacological treatment, consistent with clinical trial protocols [20]
- This substance is NOT approved for general use and must only be accessed through formal clinical trials; unregulated vendor versions carry significant purity and dosing risks [17]
Dosage context
Retatrutide is investigational and has no approved prescribing information. In Phase 2 clinical trials, weekly subcutaneous doses of 1 mg, 4 mg, 8 mg, and 12 mg were studied, with stepwise escalation protocols [1][8]. Starting at 2 mg (rather than 4 mg) was shown to reduce nausea incidence [8]. The 12 mg dose achieved the greatest weight loss (24.2% at 48 weeks) but also the highest rate of GI adverse events [7]. Final approved doses and titration schedules have not been determined; these are trial-context figures, not prescription guidance, and finalised dosing awaits regulatory review [19].
Sources
- 1.Patsnap Synapse — Retatrutide Mechanism of Action
- 2.Wikipedia — Retatrutide
- 3.Lotilabs — Retatrutide Triple Agonist Mechanisms
- 4.PeptideDeck — Retatrutide Peptide Guide 2026
- 5.Nature Medicine — Triple Hormone Receptor Agonist for MASLD (Phase 2a)
- 6.PMC / NIH — Triple Agonism Based Therapies for Obesity
- 7.NEJM — Triple-Hormone-Receptor Agonist Retatrutide for Obesity (Phase 2)
- 8.Lola Health — Retatrutide Side Effects (Full Safety Data)
- 9.Lola Health — Retatrutide Clinical Trials / Phase 3 TRIUMPH
- 10.PMC — Efficacy and Safety of Retatrutide: Systematic Review & Meta-analysis
- 11.Noom — Retatrutide Side Effects and Safety
- 12.Alzheimer's Drug Discovery Foundation — Retatrutide (Drug in Development)
- 13.Chemist Click — Retatrutide Side Effects: Clinical Trials
- 14.Bolt Pharmacy UK — Pros and Cons of Retatrutide
- 15.Lola Health — Retatrutide Side Effects (contraindication section)
- 16.Bolt Pharmacy UK — Key Safety Concerns
- 17.Alturas Medical — Retatrutide Medication Overview
- 18.Brazilian Butt Lift Blog — Retatrutide Contraindications
- 19.UFL College of Pharmacy — Retatrutide Clinical Trial Adverse Effects
- 20.Infiniskin — Retatrutide: Mechanism, Clinical Evidence, Dosage
This information is provided for educational and harm-reduction purposes only. It is not medical advice. These substances can carry serious health risks; effects and safe use vary by individual. Consult a qualified healthcare professional before use. Legal status varies by country — it is your responsibility to know your local law. We do not encourage misuse.
Other options for Retatrutide· 16 offers
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| Brand | Form | Strength | Pack | Price | Per mg |
|---|---|---|---|---|---|
Generic | — | — | 39,90 € | — | |
Generic | — | — | 93,90 € | — | |
Generic | — | — | 99,99 € | — | |
Generic | — | — | 119,99 € | — | |
Generic | vial | 10 mg | 1 vial | 159,99 € | — |
Generic | vial | 20 mg | 1 vial | 169,99 € | — |
GenericSelected | vial | 5 mg | 10 vial | 179,99 € | — |
Generic | vial | 10 mg | 10 vial | 219,99 € | — |
Generic | vial | 15 mg | 10 vial | 256,90 € | — |
Generic | vial | 20 mg | 10 vial | 259,99 € | — |
Generic | vial | 20 mg | 1 vial | 299,99 € | — |
Generic | vial | 30 mg | 10 vial | 339,99 € | — |
Generic | vial | 60 mg | 10 vial | 379,99 € | — |
Generic | vial | 50 mg | 10 vial | 389,99 € | — |
Generic | vial | 10 mg | 50 vial | 700,00 € | — |
Generic | vial | 10 mg | 10 vial | 1 200,00 € | — |