A man in his mid-30s with longstanding type 1 diabetes self-administered an online-sourced product marketed as retatrutide — a GIP/GLP-1/glucagon triple receptor agonist under clinical investigation — for weight loss without medical supervision. He presented with severe vomiting, diarrhoea, hyperglycaemia, peak ketonaemia of 4.3 mmol/L, and acute kidney injury. His partner, who took the same preparation, also developed gastrointestinal symptoms. Stool culture confirmed Shigella flexneri, though causation between retatrutide exposure and symptom severity remains undetermined. Intravenous insulin and fluids prevented full DKA, but recurrent hypoglycaemia during recovery required dextrose infusion and insulin adjustment.
This case crystallizes a collision of three converging trends: the explosive gray-market trade in research peptides, the GLP-1 agonist weight-loss phenomenon, and the underappreciated fragility of insulin-dependent metabolism during intercurrent illness. Retatrutide's glucagon receptor agonism is particularly concerning in type 1 diabetes — unlike type 2, there is no functional beta-cell reserve to modulate ketogenesis, meaning glucagon stimulation during insulin omission can accelerate ketotic crisis. The concurrent Shigella infection creates genuine diagnostic ambiguity, but the partner's shared symptoms from the same vial raise legitimate product-safety questions independent of infection. As a single case report, causality cannot be established, and the unverified purity of the online product adds further confounding. The clinical lesson is unambiguous: incretin-based research peptides carry real metabolic risk in T1DM, and their unregulated online availability is a patient safety crisis clinicians should actively flag.