In hypocalcemia, the calcium level in blood is too low.
Although most of the body's calcium is stored in bones, some circulates in the blood (see see Overview of Calcium). About 40% of the calcium in blood is attached (bound) to proteins in blood, mainly albumin. Protein-bound calcium acts as a reserve but has no active function in the body. Only unbound calcium affects the body's functions. Thus, hypocalcemia causes problems only when the level of unbound calcium is low. Unbound calcium has an electrical (ionic) charge, so it is called ionized calcium.
Hypocalcemia most commonly results when too much calcium is lost in urine or when not enough calcium is moved from bones into the blood. Causes of hypocalcemia include the following:
The calcium level in blood can be moderately low without causing any symptoms. If levels of calcium are low for long periods, people may develop dry scaly skin, brittle nails, and coarse hair. Muscle cramps involving the back and legs are common. Over time, hypocalcemia can affect the brain and cause neurologic or psychologic symptoms, such as confusion, memory loss, delirium, depression, and hallucinations. These symptoms disappear if the calcium level is restored.
An extremely low calcium level may cause tingling (often in the lips, tongue, fingers, and feet), muscle aches, spasms of the muscles in the throat (leading to difficulty breathing), stiffening and spasms of muscles (tetany), seizures, and abnormal heart rhythms.
Hypocalcemia is often detected by routine blood tests before symptoms become obvious. Doctors measure the total calcium level (which includes calcium bound to albumin) and the albumin level in blood to determine whether the level of unbound calcium is low.
Blood tests are done to evaluate kidney function and to measure magnesium, phosphate, parathyroid hormone, and vitamin D levels. Other substances in blood may be measured to help determine the cause.
Calcium supplements, given by mouth, are often all that is needed to treat hypocalcemia. If a cause is identified, treating the disorder causing hypocalcemia or changing drugs may restore the calcium level.
Once symptoms appear, calcium is usually given intravenously. Taking vitamin D supplements helps increase the absorption of calcium from the digestive tract.
Last full review/revision July 2013 by James L. Lewis, III, MD