B Vitamins help many enzymes in your body carry out chemical reactions necessary to maintain your metabolism. Some people may need a little more than others, but the good news is that these are very safe. Most of them are required in amounts of a few milligrams and are safe at several hundred milligrams. The only two that are a potential concerns are folic acid and vitamin B12. If you have a disease called Pernicious Anemia or have had your stomach removed, you cannot absorb vitamin B12. If you take folic acid in amounts greater than 0.4 milligrams you may develop problems with your nervous system. That is why multivitamins, the best way to get your B vitamins typically have a limit of 0.4 mg or 400 micrograms of folic acid. Prenatal vitamins have 800 micrograms of folic acid needed to help prevent birth defects. You will find B vitamins in your shake, many foods, and in supplements. They are excreted in your urine so you need to have them in your diet every day.