Calcium is the most abundant mineral in the body. An average healthy male contains 2.5 to 3 pounds of calcium, while an average healthy female contains about 2 pounds. Approximately 99% of the body’s calcium supply is found in the bones and teeth, leaving only 1% in the cells and body fluids. Calcium is essential for not only strong teeth and bones, but also for proper nerve impulse transmission, enzyme function, blood clotting, and energy production. The level of calcium in the body is regulated by a complex feedback loop – a pathway that controls a certain physiological function – involving parathyroid hormone (PTH), vitamin D, and calcitonin. The amount of magnesium and phosphorus in the body also affects calcium levels. It’s important that you consume an adequate amount of calcium, which is found in a variety of foods such as leafy green vegetables. As you age, be sure to maintain adequate intake of the mineral, since both high and low levels can increase your chances of developing conditions relating to the bones, heart, kidneys, nerves, and teeth. Hypercalcemia (high calcium) can put you at risk for kidney problems, for example, while long-term Hypocalcemia (low calcium) typically leads to osteoporosis – the gradual thinning of bone tissue and loss of bone density.
A blood calcium test (also called an ionized calcium test) indicates the amount of calcium in the blood, not the bones. This amount is reflected in the results of a total calcium test, which measures both free (circulating) and bound forms of calcium in the blood. The optimal reference ranges for calcium are referenced here:
A urine calcium test may also be ordered if, for instance, a person is exhibiting classic symptoms of kidney stones.