Medical information about an investigational weight-loss medication. Retatrutide is an investigational once-weekly injectable medication being studied for obesity and related metabolic conditions. It is a triple receptor agonist that targets GLP-1, GIP, and glucagon receptors. Retatrutide is not currently FDA-approved and should not be represented as an available FDA-approved weight-loss treatment.
At Weight Loss Clinic Los Angeles, our goal is to help patients understand emerging obesity treatments while making current treatment decisions using evidence-based, medically appropriate options. Patients interested in weight management can undergo a comprehensive physician evaluation to determine which currently available treatment options may be appropriate for their individual health needs.
Retatrutide (LY3437943) is an investigational medication developed by Eli Lilly. Unlike medications that activate one or two metabolic hormone receptors, retatrutide activates three: glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and glucagon receptors. Researchers are studying whether this combination can influence appetite, energy intake, glucose metabolism, and energy expenditure in ways that produce clinically meaningful weight reduction.
GLP-1
A GLP-1 receptor agonist used in FDA-approved formulations for specific indications, including chronic weight management.
GIP + GLP-1
A dual incretin receptor agonist available in FDA-approved formulations for specific indications, including chronic weight management.
GIP + GLP-1 + glucagon
An investigational triple agonist currently being studied in clinical trials. It is not FDA-approved.
| Medication | Primary receptor activity | Current role |
|---|---|---|
| Semaglutide | GLP-1 receptor agonist | FDA-approved formulations are available for specific indications including chronic weight management and type 2 diabetes. |
| Tirzepatide | GIP + GLP-1 receptor agonist | FDA-approved formulations are available for specific indications including chronic weight management and type 2 diabetes. |
| Retatrutide | GIP + GLP-1 + glucagon receptor agonist | Investigational; being evaluated in clinical trials and not FDA-approved. |
The additional glucagon-receptor activity is one of the major scientific differences between retatrutide and currently available incretin-based medications. However, a different mechanism does not automatically mean that a medication is better for an individual patient. Long-term efficacy, safety, tolerability, contraindications, and clinical outcomes must be established through appropriate trials and regulatory review.
In a randomized phase 2 obesity trial involving 338 adults, participants receiving retatrutide experienced dose-dependent weight reduction. At 48 weeks, mean weight change was approximately 17.1% in the combined 4-mg group, 22.8% in the combined 8-mg group, and 24.2% in the 12-mg group, compared with 2.1% with placebo. These are clinical-trial averages and should not be interpreted as a prediction or guarantee of an individual patient’s results.
Phase 3 studies in the TRIUMPH clinical development program have continued evaluating retatrutide in obesity and obesity-related conditions. Clinical-trial findings must be interpreted in the context of study design, participant characteristics, duration, adverse events, and subsequent regulatory review.
No. Retatrutide remains investigational and has not been approved by the FDA or another regulatory agency as a prescription treatment. Products marketed online or elsewhere as commercially available “retatrutide” should not be assumed to be the investigational product used in Lilly-sponsored clinical trials. Eli Lilly specifically warns against taking products claiming to be retatrutide outside its sponsored clinical trials.
In the phase 2 obesity trial, the most frequently reported adverse events were gastrointestinal and were generally mild to moderate, with greater frequency at higher doses. Dose-dependent increases in heart rate were also observed, peaking during the study and subsequently declining. Because retatrutide remains investigational, its complete safety profile, long-term risks, contraindications, and optimal use have not yet been established.
Possibly, but it is too early to determine how retatrutide should ultimately be positioned relative to semaglutide or tirzepatide in routine clinical practice. Head-to-head considerations include efficacy, tolerability, safety, comorbid conditions, cardiovascular and metabolic outcomes, accessibility, regulatory indications, and individual patient response. Until regulatory review is complete, currently approved treatments remain the appropriate clinical options when indicated.
Weight management should involve more than choosing an injection. Our comprehensive initial physician evaluation is designed to establish care and review medical history, symptoms, current medications, previous treatments, lifestyle factors, and health goals. When clinically appropriate, laboratory testing may be ordered to investigate medical conditions or contributing factors such as thyroid or other hormonal abnormalities, metabolic abnormalities, and vitamin or nutritional deficiencies.
Following evaluation, an individualized treatment plan may include an FDA-approved weight-management medication when appropriate, nutrition and lifestyle interventions, treatment of identified deficiencies or medical conditions, and ongoing physician monitoring.
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Follow-Up Physician Visit: $250
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Retatrutide is investigational and is not currently an FDA-approved prescription weight-loss medication. Patients should be cautious about products sold online or by clinics claiming to provide commercial retatrutide outside legitimate clinical research.
No. Semaglutide primarily activates the GLP-1 receptor. Retatrutide is being developed as a triple agonist targeting GIP, GLP-1, and glucagon receptors.
No. Tirzepatide activates GIP and GLP-1 receptors, while retatrutide additionally activates the glucagon receptor.
In the published phase 2 obesity trial, the highest-dose group had a mean weight reduction of 24.2% at 48 weeks. Results varied by dose and participant, and clinical-trial averages do not predict an individual person’s results.
We do not present investigational retatrutide as an FDA-approved commercially available treatment. We can evaluate patients interested in medical weight management and discuss evidence-based, currently appropriate treatment options while following developments in retatrutide research.
Retatrutide includes GLP-1 receptor activity, but it is more accurately described as an investigational triple agonist because it also activates GIP and glucagon receptors. The informal term “GLP-3” is not a recognized scientific drug class.
No. Retatrutide is investigational and is not FDA approved. The FDA states that retatrutide cannot be used in compounding under federal law and has warned about products marketed as retatrutide outside legitimate clinical research.
Retatrutide is being studied in Phase 3 programs for obesity, type 2 diabetes and several obesity-related conditions. Some Phase 3 topline results have been announced, while additional studies and regulatory review remain ongoing.
Retatrutide is designed to activate GIP, GLP-1 and glucagon receptors. Researchers are studying how this combined activity may affect appetite, energy intake, glucose metabolism and energy expenditure.
That has not been established for routine clinical care. Retatrutide remains investigational, and cross-trial percentages should not be treated as a direct head-to-head comparison. Treatment decisions should consider regulatory approval, safety, medical history, comorbidities, tolerability and individual response.
There is no guaranteed public availability date. Availability depends on completion of the clinical development program, regulatory review and any eventual approval.
The FDA states that retatrutide cannot be used in compounding under federal law. Products marketed as compounded or commercially available retatrutide should not be assumed to be equivalent to the investigational medicine studied in clinical trials.
In the published Phase 2 obesity trial, gastrointestinal adverse events were the most common and were generally mild to moderate. Dose-dependent increases in heart rate were also observed. Because development is ongoing, the complete long-term safety profile has not yet been established.
Jastreboff AM, Kaplan LM, Frías JP, et al. Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. New England Journal of Medicine. 2023;389:514-526. ClinicalTrials.gov NCT04881760.
Eli Lilly and Company. Retatrutide clinical development and TRIUMPH program information. Accessed September 2026.
Written and medically reviewed by David Nazarian, MD
Board Certified in Internal Medicine
Last medically reviewed: September 2026.
This page is for educational purposes and does not replace individualized medical advice. Retatrutide is investigational and is not FDA-approved. Treatment recommendations require an individual medical evaluation.
