How much vitamin b-12 should you take daily?

There are a spectrum of B-vitamins. I've included the "official" requirements per governmental agencies. Notice that these are much lower than stated quantities on most multivitamin preparations, which take into account only amounts necessary for a general population average group to avoid clinical deficiency states (a worst case scenario), and not quantities widely thought of as promoting changing requirements for each person. B1 (thiamine) 10-50 mg B2 (riboflavin) 10-50mg B3(niacin) 25mg B6(pyridoxine)25mg B12 (cobalamin) 50 mcg pantothenic acid 25mg folic acid 400 mcg Age, anemia, vegetarianism, Alcoholism and nutritional habits may all increase the need for additional supplementation; Note: gender and stress do not have additional requirements, except for pregnant women.