hypokalsemia

Hypocalcemia is a lower-than-normal level of calcium in the blood. Normal values can vary by laboratory, but total serum calcium is often considered low when it falls below about 2.2 mmol/L (8.8 mg/dL) and ionized calcium below about 1.1 mmol/L. Because calcium is partly bound to albumin, corrected calcium is sometimes used in patients with abnormal albumin levels, calculated as corrected calcium = measured calcium + 0.8 × (4 − albumin in g/dL).

Symptoms can include numbness or tingling around the mouth, muscle cramps, carpopedal spasm, tetany, seizures, and irritability. Exam findings may include a positive Chvostek sign or Trousseau sign. Cardiac involvement can manifest as QT interval prolongation on electrocardiography. Severe hypocalcemia can cause laryngospasm or life-threatening arrhythmias.

Causes are diverse and commonly involve impaired parathyroid hormone (PTH) function, vitamin D deficiency or resistance, and factors associated with altered calcium and phosphate metabolism. Typical etiologies include hypoparathyroidism (often after neck surgery or autoimmune disease), chronic kidney disease with hyperphosphatemia and reduced calcitriol, magnesium deficiency, and malabsorption or nutritional deficiency. Certain medications and acute illnesses can contribute. Distinguishing true hypocalcemia from low total calcium with low albumin is important.

Diagnosis relies on measuring serum calcium with albumin correction and, if needed, ionized calcium. Evaluation usually includes parathyroid hormone level, magnesium, phosphate, and vitamin D status, along with clinical assessment. ECG monitoring may help assess risk in those with cardiac involvement.

Management depends on severity and symptoms. Acute symptomatic hypocalcemia requires prompt intravenous calcium, typically calcium gluconate, with monitoring and correction of any magnesium deficiency. Chronic management may involve oral calcium supplementation and active vitamin D (calcitriol), along with treatment of the underlying cause and regular monitoring for calcium and phosphate levels.