After potassium, magnesium is the second most prevalent cation in the intracellular fluid. The normal concentration of magnesium is 1.8 to 2.7 mEq/L with very little found in the extracellular fluid and approximately 60% located in the bones. Magnesium is similar to calcium in that it is found either ionized in a physiologically active form (approximately two-thirds) or bound, primarily with albumin, and considered physiologically inactive (one-third).