Measurement of the serum calcium level is useful for determining the cause of kidney or thyroid problems and if an appropriate amount of vitamin D in the person's body.
All cells require calcium for numerous functions.
Calcium is especially important in the structure of bones and in neuromuscular activity. About half of the calcium in the serum is loosely associated with proteins . The accuracy of this method depends on having normal amounts of binding proteins. If the levels of binding proteins are increased or decreased, the amount of serum calcium will appear to be increased or decreased, because it is the free calcium that is regulated hormonally by the body. In these circumstances, ionized calcium is a more reliable measure of calcium levels.