is bpc 157 peptide fda approved Survey: Half of Peptide-Users Aren't Aware of Approval Status RFK Jr pushes for FDA
Description
Neurosci ., 53 , 211213
This is due to the inhibition of DNA synthesis (specifically purines and thymidine)

Another 44% of those who did not have regular cycles (due to long-acting contraceptives or gender affirming treatments) reported breakthrough bleeding

Structure of vitamin B12, retrieved from PubChem Compound Database, National Center for Biotechnology

Of course, any time you are suppressing specific areas of the immune system, you have an increased risk of infection
