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Causes of decreased calcium in the blood (hypocalcemia)
Last reviewed: 06.07.2025
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The most common cause of decreased total serum calcium is hypoalbuminemia. If the ionized calcium content is within normal limits, calcium metabolism in the body is not impaired. Causes of decreased serum ionized calcium concentration:
- renal failure;
- hypoparathyroidism (of unknown etiology or postoperative);
- severe hypomagnesemia;
- hypermagnesemia;
- acute pancreatitis;
- skeletal muscle necrosis;
- tumor disintegration;
- avitaminosis D.
Low calcium levels are sometimes observed in seriously ill patients without apparent cause.
The clinical manifestations of hypocalcemia vary depending on the degree and rate of calcium loss. Increased excitability of nerves and muscles leads to paresthesia and tetany, including tonic spasms of the muscles of the hands and feet. Positive signs of Trousseau and Chvostek indicate latent tetany. Severe hypocalcemia causes drowsiness, confusion, and rarely laryngeal spasm, seizures, and reversible heart failure. The QT interval is prolonged on the ECG.