Retatrutide is Eli Lilly’s latest investigational weight loss medication developed to address obesity through a triple-action mechanism. Unlike earlier medications that act on one or two hormone receptors, Retatrutide targets three key metabolic pathways — GLP-1 (glucagon-like peptide-1), GIP (glucose-dependent insulinotropic polypeptide), and glucagon receptors — to help regulate appetite, control energy balance, and support fat metabolism.
This triple-agonist mechanism is being studied for its potential to explore broader metabolic effects compared with existing GLP-1 and dual-agonist treatments such as semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro).
In a Phase 2 clinical trial published in the New England Journal of Medicine, participants treated with Retatrutide showed an average body-weight reduction of about 24 percent over 48 weeks — a substantial decrease observed in early clinical research.
The medication has also generated international media coverage. Publications such as Dazed Digital and Business Insider have referred to Retatrutide as the “Godzilla of weight loss injections,” describing its early clinical data and increasing public attention. While this nickname highlights increasing public attention, Retatrutide remains in the research phase and is not yet approved for medical use.
Ongoing Phase 3 studies will determine its long-term safety, efficacy, and suitability for medical practice. Although not yet available in Singapore, Retatrutide may become a potential future addition to doctor-prescribed medical weight management once regulatory approval is granted.
Retatrutide is an investigational triple-agonist weight loss injection developed by Eli Lilly, designed to support medical management of obesity and related metabolic conditions. It acts on three key hormone receptors — GLP-1 (glucagon-like peptide-1), GIP (glucose-dependent insulinotropic polypeptide), and glucagon — to deliver a more comprehensive metabolic effect than existing single- or dual-agonist drugs.
By combining these three hormonal pathways, Retatrutide aims to improve appetite control, enhance glucose metabolism, and promote fat reduction, while also helping to maintain lean muscle mass. Its mechanism of action is currently being studied in large-scale clinical trials to evaluate both safety and long-term efficacy.
Retatrutide works through a triple-agonist mechanism that targets three major hormone receptors involved in appetite regulation and energy metabolism: GLP-1 (glucagon-like peptide-1), GIP (glucose-dependent insulinotropic polypeptide), and glucagon. By acting on all three pathways simultaneously, Retatrutide is designed to create a more complete and sustained approach to weight loss than current single- or dual-agonist medications.
The GLP-1 and GIP receptors help control hunger, increase satiety, improve insulin sensitivity, and slow gastric emptying. Together, these effects reduce food intake and promote more stable post-meal glucose levels. The glucagon receptor works differently, helping to increase energy expenditure and enhance fat oxidation, supporting the breakdown of stored fat into usable energy.
By combining these effects, Retatrutide promotes calorie reduction while supporting healthy metabolic function. Early research suggests that this triple-agonist approach may result in more consistent and long-lasting weight loss, alongside improvements in lipid levels and cardiovascular risk factors.
This multi-pathway model builds on existing GLP-1 and dual-agonist therapies such as semaglutide and tirzepatide but extends their metabolic benefits. Eli Lilly developed Retatrutide to explore whether targeting an additional hormone receptor could overcome the limitations seen with earlier treatments, such as plateauing results or reduced long-term responsiveness.
Ongoing studies continue to evaluate how this mechanism affects fat-to-lean-mass ratios and long-term body composition. These findings will help determine whether Retatrutide can offer a sustainable, medically supervised approach to weight management once approved.
Retatrutide was developed by Eli Lilly following the clinical success of its earlier GLP-1 and dual-agonist agents. It represents the next stage in the company’s metabolic research pipeline, intended to address limitations observed in previous therapies.
Early research demonstrated that triple-hormone activation could provide stronger appetite suppression and improved fat-to-lean-mass ratios in preclinical models. Building on these findings, Eli Lilly initiated human clinical studies to confirm these effects, focusing on non-diabetic individuals with obesity and, separately, those with type 2 diabetes.
Results from ongoing trials will determine its eventual role in the broader treatment landscape once approved for use.
Retatrutide has demonstrated strong early outcomes in clinical studies, showing potential to achieve greater weight loss compared with currently approved GLP-1 or dual-agonist medications. The most significant findings to date come from an international Phase 2 clinical trial published in 2023, which evaluated the efficacy and safety of Retatrutide in adults with obesity or overweight.
In this study, participants received varying doses of Retatrutide once weekly for 48 weeks. Those in the highest dose group achieved an average 24.2% reduction in body weight, compared with 0.4% in the placebo group. These results indicate that Retatrutide may deliver clinically meaningful and sustained weight loss when combined with healthy lifestyle habits.
Participants also showed improvements in several metabolic parameters, including fasting glucose, insulin sensitivity, lipid profile, and blood pressure. These findings suggest that Retatrutide may not only promote weight reduction but also improve overall cardiometabolic health.
The treatment was generally well-tolerated, with the most common side effects being mild to moderate gastrointestinal symptoms such as nausea, diarrhoea, and decreased appetite. Most side effects occurred early in treatment and tended to subside over time as the body adapted to the medication.
Phase 3 clinical trials are currently underway to confirm these findings across broader populations and to determine long-term outcomes. Pending successful results and regulatory review, Retatrutide could become one of the most effective prescription weight loss injections available in future years.
As of now, Retatrutide is not yet available in Singapore or any other country for prescription use. The medication remains in the clinical trial phase and has not been approved by major health authorities such as the United States Food and Drug Administration (FDA) or Singapore’s Health Sciences Authority (HSA).
Eli Lilly is currently conducting Phase 3 studies to assess the long-term safety and effectiveness of Retatrutide for obesity and metabolic disorders. Once these trials are completed and regulatory reviews are finalised, the company may seek approval for global use. Based on typical review timelines, Retatrutide’s availability in Singapore is expected to be after 2026, depending on international approvals and local registration processes.
For patients in Singapore seeking medical weight loss options today, it is important to note that only approved and regulated medications such as semaglutide (Ozempic, Wegovy), tirzepatide (Mounjaro), and oral semaglutide (Rybelsus) can currently be prescribed under doctor supervision. These treatments are clinically validated, legally available, and supported by established safety data.
Patients interested in Retatrutide can stay informed through trusted medical updates and should avoid unverified or grey-market versions of the drug being sold online. Such products are unregulated and potentially unsafe. Always consult a licensed doctor before starting or purchasing any injectable weight loss medication.
Retatrutide is part of the latest generation of medical treatments being developed to address obesity through hormonal pathways. Over recent years, injectable medications such as semaglutide and tirzepatide—marketed globally under brand names like Ozempic, Wegovy, and Mounjaro—have gained recognition for their ability to help regulate appetite and improve metabolic function under medical supervision. These medications act primarily on the GLP-1 or dual GLP-1 and GIP receptors, which influence hunger, satiety, and glucose control.
Retatrutide builds upon this scientific foundation by adding activation of the glucagon receptor to the GLP-1 and GIP pathways. This triple-agonist approach is being investigated for its ability to further enhance metabolic regulation, increase energy expenditure, and promote sustainable weight loss. It represents the next step in a research pathway aimed at improving the body’s hormonal response to weight management.
While Ozempic, Wegovy, and Mounjaro are already approved and available in Singapore for eligible patients, Retatrutide remains under clinical investigation and has not yet received regulatory approval. Its ongoing trials reflect continued advancement in the field of medical weight loss therapy, with the goal of providing more diverse and personalised treatment options in the future.
Patients who wish to explore currently approved and doctor-supervised treatments may discuss options such as semaglutide or tirzepatide with a licensed medical practitioner to determine the most suitable plan for their individual goals.
In Singapore, several clinically approved medications are available to support safe and effective medical weight loss under a doctor’s supervision. These treatments work through scientifically established hormonal pathways to help reduce appetite, regulate calorie intake, and improve metabolic balance.
Among the available options are:
These medications are prescribed as part of a structured, doctor-monitored programme that includes medical assessment, dose adjustments, and ongoing follow-up to ensure safe and sustainable results. Each treatment plan is customised based on the patient’s medical profile, goals, and treatment response.
It is important to note that medications such as Retatrutide remain in clinical development and are not yet available for public use. Until new therapies are approved, doctor-prescribed options like semaglutide, tirzepatide, and oral GLP-1 medications remain the mainstay of evidence-based weight management in Singapore.
Patients who wish to explore suitable weight loss options can schedule a consultation with a qualified physician.
In Singapore, doctor-prescribed and approved medical weight loss options include:
These medications are available under medical supervision as part of a structured and personalised weight management plan.
Dr Edwin Lim
MBBS (Singapore), MRCS (Edinburgh), PgDip Practical Dermatology (Cardiff), MSc Practical Dermatology (Cardiff), Diploma in Aesthetic Medicine, (AAAM), Accredited by the Aesthetic Dermatology Educational Group (ADEG)
