Research grade incretin receptor agonists, the class usually searched as weight loss peptides. Three generations: semaglutide 8mg acts at GLP-1 alone, tirzepatide 40mg adds GIP, and retatrutide 40mg adds glucagon on top of both. Semaglutide and tirzepatide have licensed counterparts prescribed in the UK; retatrutide has none and remains in Phase 3. Newer does not mean better established. None of these is a licensed medicine in the form supplied here. All are for laboratory research use only, not for human or veterinary consumption, and none may be advertised with therapeutic claims. Cost per milligram is only comparable within a compound, since each is used at a different scale. Read next: tirzepatide vs semaglutide, retatrutide vs Mounjaro, side effects and trial limits, the full range.