A low calcium level may result from a problem with the parathyroid glands, as well as from diet, kidney disorders, or certain medications.
As hypocalcemia progresses, muscle cramps are common, and people may become confused, depressed, and forgetful and have tingling in their lips, fingers, and feet as well as stiff, achy muscles.
Usually, the disorder is detected by routine blood tests.
Calcium and vitamin D supplements may be used to treat hypocalcemia.
(See also Overview of Electrolytes Overview of Electrolytes More than half of a person's body weight is water. Doctors think about water in the body as being restricted to various spaces, called fluid compartments. The three main compartments are Fluid... read more and Overview of Calcium's Role in the Body Overview of Calcium's Role in the Body Calcium is one of the body's electrolytes, which are minerals that carry an electric charge when dissolved in body fluids such as blood, but most of the body's calcium is uncharged. (See also... read more .)
Calcium is one of the body's electrolytes Overview of Electrolytes More than half of a person's body weight is water. Doctors think about water in the body as being restricted to various spaces, called fluid compartments. The three main compartments are Fluid... read more , which are minerals Overview of Minerals Minerals are necessary for the normal functioning of the body’s cells. The body needs relatively large quantities of Calcium Chloride Magnesium read more that carry an electric charge when dissolved in body fluids such as blood (but most of the body's calcium is uncharged). Although most of the body's calcium Overview of Calcium's Role in the Body Calcium is one of the body's electrolytes, which are minerals that carry an electric charge when dissolved in body fluids such as blood, but most of the body's calcium is uncharged. (See also... read more is stored in bones, some circulates in the blood.
About 40% of the calcium in blood is attached (bound) to proteins in blood, mainly albumin. Protein-bound calcium acts as a reserve source of calcium for the cells 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 also called ionized calcium.
Causes of Hypocalcemia
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:
A low level of parathyroid hormone (hypoparathyroidism Hypoparathyroidism Hypoparathyroidism is a deficiency of parathyroid hormone (PTH) often caused by an autoimmune disorder, treatment-related damage to the parathyroid glands, or removal of the glands during surgery... read more ), as can occur when the parathyroid glands are damaged during thyroid gland surgery
Lack of response to a normal level of parathyroid hormone (pseudohypoparathyroidism)
A low level of magnesium (hypomagnesemia Hypomagnesemia (Low Level of Magnesium in the Blood) In hypomagnesemia, the level of magnesium in blood is too low. (See also Overview of Electrolytes and Overview of Magnesium's Role in the Body.) Magnesium is one of the body's electrolytes,... read more ), which reduces the activity of parathyroid hormone
Vitamin D deficiency Vitamin D Deficiency Vitamin D deficiency is most commonly caused by a lack of exposure to sunlight. Some disorders can also cause the deficiency. The most common cause is lack of exposure to sunlight, usually when... read more (due to inadequate consumption or inadequate exposure to sunlight)
Kidney dysfunction, which results in more calcium excreted in urine and makes the kidneys less able to activate vitamin D
Inadequate consumption of calcium
Disorders that decrease calcium absorption
Certain medications, including rifampin (an antibiotic), antiseizure medications (such as phenytoin and phenobarbital), bisphosphonates (such as alendronate, ibandronate, risedronate, and zoledronic acid), calcitonin, chloroquine, corticosteroids, and plicamycin
Symptoms of Hypocalcemia
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 Seizure Disorders In seizure disorders, the brain's electrical activity is periodically disturbed, resulting in some degree of temporary brain dysfunction. Many people have unusual sensations just before a seizure... read more , and abnormal heart rhythms Overview of Abnormal Heart Rhythms Abnormal heart rhythms (arrhythmias) are sequences of heartbeats that are irregular, too fast, too slow, or conducted via an abnormal electrical pathway through the heart. Heart disorders are... read more 
.
Diagnosis of Hypocalcemia
Measurement of calcium level in the blood
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.
Treatment of Hypocalcemia
Calcium supplements
Sometimes vitamin D
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 medications 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.
Sometimes people with hypoparathyroidism are given a synthetic form of parathyroid hormone.
