Magnesium is the fourth most abundant mineral in the body and is essential to good health. Approximately 50% of total body magnesium is found in bone. The other half is found predominantly inside cells of body tissues and organs. Only 1% of magnesium is found in blood. Studies performed on the importance of magnesium and the medical conditions that may arise from inadequate magnesium in the body have increased the interest of magnesium supplementation. Magnesium, an important electrolyte needed for proper muscle, nerve, and enzyme function, is also used as a supplement to relieve premenstrual symptoms related to mood changes. Studies indicate that some of the medical conditions that may arise from inadequate magnesium are hypertension, hear arrhythmias, diabetes, osteoporosis, migraines, premature ejaculation, premenstrual syndrome, and insomnia, to list a few. Compounding pharmacists can consult with patients and assist them with magnesium supplements that are prepared specifically for their health needs.