WEIGHT MANAGEMENT
Retatrutide
Also known as LY3437943, Eli Lilly retatrutide
Retatrutide is an investigational peptide in phase 3 development (the TRIUMPH programme, Eli Lilly). Phase 2 results published in 2023 reported mean weight reductions around 22 to 24 percent at 48 weeks at higher doses. It was not approved or commercially available in mid-2026; access was limited to clinical trials.
Reference dose range
1000–12000 mcg
Reported frequency
Once weekly, with gradual escalation, in trial settings
Reported routes
Subcutaneous
Approximately six days, supporting once-weekly subcutaneous dosing.
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Mechanism
Retatrutide is an investigational triple agonist acting at the GLP-1, GIP, and glucagon receptors. The GLP-1 and GIP components affect insulin secretion, satiety, and gastric emptying, while glucagon-receptor activity is associated with increased energy expenditure and hepatic fat oxidation. This third mechanism distinguishes it from dual agonists such as tirzepatide.
Reported effects
Large mean weight reduction at 48 weeks (strong phase 2 human data)
Reduction in HbA1c in type 2 diabetes (phase 2, moderate human evidence)
Marked reduction in liver fat in phase 2 studies
Cardiometabolic signals under evaluation in phase 3
Commonly reported side effects
Nausea, vomiting, diarrhoea, and constipation, as class effects of incretin agonists
Administration-site reactions
Thyroid C-cell class warning expected, pending final labelling
Weight regain after discontinuation, a class effect
Certainty and limits
Retatrutide was not approved by regulators in mid-2026. The phase 2 and early phase 3 data are strong, but glucagon-receptor agonism adds metabolic complexity relative to single and dual agonists. It is not commercially available; access is via clinical trial only.
This is part of the reviewed public subset. The signed-in app includes a broader peptide reference library alongside private tracking tools.