What it is

Vitamin B12 is a group of cobalamins, each a large ring with a cobalt atom at its centre and a different group hanging off it: cyanocobalamin, hydroxocobalamin, methylcobalamin and adenosylcobalamin. Only bacteria make it, animals store it, and humans must take it in. Two of those forms, methyl and adenosyl, are the ones your enzymes actually use, and the others are converted inside the cell. It is a vitamin, not a peptide, and the injectable liquid is a true replacement rather than an enhancement.