B12 is a prescription drug, it is used for many things such as nerve issues, metabolism, pernicious anemia and so on. If your eating meat protiens and have a large enough amount of IF in your gut which you should, taking more is pretty useless. It really just makes you have expensive Urine. But, if you are so in to taking it, go to a feed store and buy the vet version for about 20 bucks B12 is B12. Just so you know the liver stores about 3-5 years of B12.