Vitamin B12 has a unique place for nutrition. The body needs only a very minute amount of this vitamin, in micrograms, yet without it severe, far-reaching, and in some cases irreversible consequences will result. Asking why deficiency in B12 is so dangerous can be considered equivalent asking why deficiency in B12 is so dangerous, because actually the vitamin itself, either consumed from food or from supplements, has no substantial toxicity even if one takes a dose higher than the normal
