Below 70 is considered "low," but it's not dangerous until it gets below 50 for men and 40 for women (according to what I read).
Read my thread below about Toxic Hunger and make sure it's not that, or else you could get yourself into a vicious cycle the rest of your life if you think it's true hypoglycemia and start eating the recommended high protein diet to remedy it, which is what actually CAUSES Toxic Hunger.