Blood tests are unreliable.
Blood magnesium often remains within the normal range even when cellular levels are unusually low. According to the late Adelle Davis, a nutritionist who received her M.S. in biochemistry from the University of Southern California Medical School, symptoms of low magnesium include hyperactivity, irritability, sensitivity to noise, muscle spasms, muscle twitches, muscle weakness, insomnia and depression. When the deficiency is severe, symptoms include confusion, disorientation, belligerent behavior, convulsions, and hallucinations. Good sources include seeds, nuts, whole grains, and cooked green leafy vegetables. Magnesium is lost when the water from cooking vegetables is discarded, or when foods are overcooked.