Vegans (people who dont consume any meat products) and people lacking intrinsic factors are at risk of vitamin B12 deficiency
While its potential as a systemic anti-aging therapeutic is heavily discussed in longevity circles, the optimal delivery method to target the central nervous system has remained speculative

Neurological: convulsions, increased intracranial pressure with papilledema (pseudotumor cerebri) usually after treatment, vertigo, headache Endocrine: menstrual irregularities, development of cushingoid state, suppression of fetal intrauterine or childhood growth, lack of secondary response of the adrenal cortex or pituitary gland, particularly in situations of stress such as trauma, surgery or illness, decreased carbohydrate tolerance, manifestations of latent diabetes mellitus, increased requirements of insulin or oral hypoglycemic agents in diabetic patients Ophtalmic: posterior subcapsular cataracts, increased intraocular pressure, glaucoma, exophthalmos Metabolic: negative nitrogen balance due to protein catabolism Psychiatric: euphoria, mood swings, severe depression to frank psychotic manifestations, personality changes, hyperirritability, insomnia Others: anaphylactoid or hypertensive reactions and hypotension or shock-like reaction Cyanocobalamin and hydroxocobalamin: hypervitaminosis and side effects were not observed with their use Dosage and administration Adults Coated tablets: 1 coated tablet 2 times a day

Alpha Oscillations Serve to Protect Working Memory Maintenance against Anticipated Distracters
J Membr Biol 111: 103111 ColombiniM (2007) Measurement of VDAC permeability in intact mitochondria and in reconstituted systems