The adult human requires approximately 2.0 to 2.2 mg of vitamin B-6 each day. Although there is not a particular disease that is solely attributable to a deficiency of vitamin B-6, a shortage can cause health problems, such as irregular glucose levels and poor immunity. Good health can also be hindered by excessively large intakes of vitamin B-6 and the Institute of Medicine has set the upper tolerable daily limit at 100 mg for adults.