The maximum suggested daily requirement is 4,000 IU per day for healthy adults, ... Greger said he takes 2,000 micrograms of vitamin B12 a week. The recommended daily allowance is 2.4 mcg daily, ...

Meeting the minimum requirement for vitamin B12, needed to make DNA, red blood cells and nerve tissue, may not actually be enough -- particularly if you are older. It may even put you at risk for ...