Calcemia

A blood calcium test measures the amount of calcium in the blood. Over 99% of the body's calcium is stored in bones as calcium phosphate or calcium carbonate, with the remaining approximately 1% found in soft tissues and extracellular fluid. The amount of calcium in the blood is very small and primarily exists as protein-bound calcium, complexed calcium (calcium bound to anions), and free calcium. Blood calcium levels are usually tightly regulated. When blood calcium levels are low (hypocalcemia), bones release more calcium to help restore normal levels. When blood calcium levels are high (hypercalcemia), excess calcium is stored in bones or excreted in urine or feces. The body's calcium levels typically depend on several factors: Dietary calcium intake. Intestinal absorption of calcium and vitamin D. Phosphate levels in the body. Levels of certain hormones in the body, such as parathyroid hormone, calcitonin, and estrogen.