Most B12 products use cyanocobalamin, which has to be metabolized by the body before it is in a usable form
(Native, unmodified recombinant human IGF-1, sold as mecasermin/Increlex, is FDA-approved only for a narrow pediatric growth-failure indication and is chemically distinct from the LR3 analog.) In the US it is manufactured and sold almost exclusively as an unregulated "research chemical" labeled "not for human consumption," a labeling practice peptide vendors use to avoid marketing it as an unapproved drug
Retatrutide has the unique dysesthesia concern that affects up to 20% of people at the highest dose
Nano-micro Lett (2022) 14(1):172
Rudman D, Feller AG, Nagraj HS, et al
This article shows that unimolecular GLP1/GIP co-agonism corrects obesity and glucose intolerance in obese rodents and non-human primates