Robbie Bekhit voted up Anonymous' answer 6/10/2016 What Will Happen If I Take Too Much Biotin? Is Biotin Really A Vitamin That Cause Hair To Thicken Biotin does not cause hair to thicken. Your hair just feels softer, but it doesn't naturally thicken. If you take too much, you will vomit. Taking too much can increase chances of strokes.