The Importance of Vitamin B12 Vitamin B12 is required for red blood cell formation and normal growth; it helps to build immunity and treats some degenerative diseases. It is used therapeutically to treat many mental and nervous disorders as well as help combat allergies and increase energy levels. So how do you know if you are getting enough? Signs of B12 Deficiency Some signs of B12 deficiency may include weakness, fatigue, diarrhea, depression, indigestion, numbness in the