B12 injections are extremely safe, even at higher doses, and adverse reactions are rare
For instance, as learned by X-ray crystallographic studies of complexes of the enzymes with glutathione alkyl thioethers as non-covalent inhibitors, in human class glutathione transferase A1-1 the sulphur atom forms a hydrogen bond to the hydroxyl group of a tyrosine and to the guanido group of an arginine [130,131,132]
Anecdotal reports of improved libido or mood lack objective hormone measurements and control groups
Yes, Vitamin injections are generally safe but may cause some mild side effects such as pain, swelling or redness at the injection site, and in rarer cases, headaches, itching, or nausea