If the levels of an electrolyte are too low, a common response to electrolyte imbalance may be to prescribe supplementation. However, if the electrolyte involved is sodium, the issue is often water excess rather than sodium deficiency. Supplementation for these people may correct the electrolyte imbalance but at the expense of volume overload. For newborn children, this has serious risks. Because each individual electrolyte affects physiological function differently, they must be considered separately when discussing causes, treatment, and complications. Calcium Though calcium is the most plentiful electrolyte in the body, a large percentage of it is used to form the bones. It is mainly absorbed and excreted through the GI system. The majority of calcium resides extracellularly, and it is crucial for the function of neurons, muscle cells, function of enzymes, and coagulation. The normal range for calcium concentration in the body is 8.5 - 10.5 mg/dL. The parathyroid gland is responsible for sensing changes in calcium concentration and regulating the electrolyte with parathyroid hormone. Hypercalcemia Hypercalcemia describes when the concentration of calcium in the blood is too high. This occurs above 10.5 mg/dL. Causes The most common causes of hypercalcemia are certain types of cancer, hyperparathyroidism, hyperthyroidism, pheochromocytoma, excessive ingestion of vitamin D, sarcoidosis, and tuberculosis. Hyperparathyroidism and malignancy are the predominant causes. It can also be caused by muscle cell breakdown, prolonged immobilization, dehydration. Symptoms The predominant symptoms of hypercalcemia are abdominal pain, constipation, kidney stones, extreme thirst, excessive urination, nausea and vomiting. In severe cases where the calcium concentration is >14 mg/dL, individuals may experience confusion, altered mental status, coma, and seizure. Treatment Primary treatment of hypercalcemia consists of administering IV fluids. If the hypercalcemia is severe and/or associated with cancer, it may be treated with bisphosphonates. For very severe cases, hemodialysis may be considered for rapid removal of calcium from the blood. Hypocalcemia Hypocalcemia describes when calcium levels are too low in the blood, usually less than 8.5 mg/dL. Causes Hypoparathyroidism and vitamin D deficiency are common causes of hypocalcemia. It can also be caused by malnutrition, blood transfusion, ethylene glycol intoxication, and pancreatitis. Symptoms Neurological and cardiovascular symptoms are the most common manifestations of hypocalcemia. Patients may experience muscle cramping or twitching, and numbness around the mouth and fingers. They may also have shortness of breath, low blood pressure, and cardiac arrhythmias. Treatment Patients with hypocalcemia may be treated with either oral or IV calcium.