Retatrutide (Pen)
Price range: £54.99 through £124.99
Retatrutide
Metabolics & GLP-1 — Triple Agonist
GIP/GLP-1/GCG triple agonist peptide
Retatrutide is an investigational once-weekly triple agonist of the GIP, GLP-1, and glucagon receptors (triple G). In the Phase II SURMOUNT dose-finding trial, 12 mg weekly produced mean body weight loss of 24.2% at 48 weeks — the highest reported for any pharmacological agent in a controlled trial.
Mechanism:
GIP + GLP-1 + glucagon triple agonist
Stage:
Phase III trials (as of 2026)
Peak Phase II Weight Loss:
24.2% at 48 weeks
Retatrutide
Mechanism of Action
Retatrutide engages three complementary receptor systems simultaneously — GIP (GIPR), GLP-1 (GLP-1R), and glucagon (GCGR) — creating the most potent known pharmacological stimulus for weight reduction yet observed in clinical trials.
Glucagon Receptor Contribution
Glucagon receptor activation increases energy expenditure through hepatic lipid oxidation, brown adipose tissue thermogenesis, and direct lipolysis. In isolation, glucagon would raise blood glucose — but the concurrent GLP-1R activation provides counterbalancing insulin stimulation, keeping glucaemic control maintained.
GIP + GLP-1 Synergy
The GIP and GLP-1 components mirror tirzepatide’s twincretin mechanism — suppressing appetite, slowing gastric emptying, and improving insulin sensitivity — while the glucagon component adds a metabolic expenditure dimension not present in dual agonists.
Phase II Results
The Phase II dose-finding trial (NCT04881760) demonstrated progressive weight loss with retatrutide at all doses tested, with 12 mg weekly producing 24.2% mean reduction in body weight at 48 weeks. Adverse effects were primarily gastrointestinal and transient, consistent with the GLP-1 agonist class.
Investigational — not yet approved. Phase III trials ongoing as of 2026. Do not attempt to source or self-administer.
Vials (Peptides)
Pre-mixed Pens (Peptides)
Nasal Spray (Peptides)
Cream (Peptides)
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