The body needs access to vitamin B12 to produce red blood cells. A lack of this vitamin can lead to anaemia.Folic acid deficiency can cause anemia. Anemia is a condition where you have too few RBCs. Anemia can deprive your tissues of oxygen it needs, because red blood cells carry the oxygen. Symptoms of a deficiency depends on what type of vitamin B you lack. They can range from fatigue and confusion, to anemia or a compromised immune system. Skin rashes also can occur.