There are 8 different forms of vitamin B. They include B1 (thiamine), B2 (riboflavin), B3 (niacin), B6 (pyridoxine), B9 (folic acid), B12 (cyanocobalamin), biotin, and pantothenic. Vitamin B plays an important role in helping the body function properly. The brain, the health of red blood cells, the heart, and the nervous system all depend on a healthy balance of vitamin B. A deficiency could result in physical and mental changes like fatigue, weakness, memory loss, anemia, and digestive problems. It may also manifest itself by showing up as black marks or dark lines on the fingernails.
A simple blood test can determine specifically which vitamin you may "B" lacking.