The amount of biotin one should take for hair growth or other purposes depends on their condition. This is a safe supplement, which is part of the Vitamin B7 family. If you take too much of it, your body will just wash it out of your system. However, one may want to begin with a small dose such as 1,000 mcg a day. If the hair is in bad condition, they can work their way up to 5,000 mcg. a day.