More typically, patients with hypocalcemia may be asymptomatic or experience milder symptoms such as muscle cramps and paresthesias. The paresthesias, described as “pins and needles” sensations in the hands, feet, and around the mouth, are episodic and often occur at times of stress, vomiting, or hyperventilation. This can be explained by the fact that metabolic or respiratory alkalosis increases the binding of serum calcium to albumin and decreases the concentration of free ionized calcium that interacts with cells.

Symptoms of hypocalcemia are also more likely to occur when the serum calcium level has fallen abruptly; chronic hypocalcemia, in contrast, can be asymptomatic with very low levels of serum calcium. Asymptomatic hypocalcemia must be differentiated from the low total serum calcium concentration (with a normal ionized calcium level) that occurs with hypoalbuminemia. The corrected total serum calcium concentration can be calculated by measuring the serum albumin level and adding 0.8 mg/dL to the total serum calcium level for each 1 g/dL reduction in the serum albumin level from 4 g/dL (corrected calcium = 0.8 × [4.0 − patient’s albumin] + serum calcium).

Tetany can be elicited in patients with no overt signs of hypocalcemia by inducing the Chvostek and Trousseau signs. The Chvostek sign is produced by tapping the facial nerves at the angle of the jaw, which causes contracture of the ipsilateral facial muscles. The Trousseau sign is elicited by applying a blood pressure cuff to the upper arm and inflating it to just above the systolic blood pressure for 3 minutes. The resulting carpopedal spasm, with contractions of the fingers and inability to open the hand, is a result of increased neuromuscular irritability caused by hypocalcemia and aggravated by ischemia. This may be painful for the patient if sustained for too long but is believed to be a more specific marker of hypocalcemia than the Chvostek sign.

Other nonspecific signs and symptoms of hypocalcemia are lethargy, psychomotor depression, and impaired cognitive function with poor school performance in children. Hypocalcemia also decreases the contractility of the heart muscle, which can provoke or aggravate congestive heart failure in patients with heart disease. In these patients, heart failure can improve with administration of calcium. Hypocalcemia also leads to prolongation of the rate-corrected QT interval on an electrocardiogram. An unusual ocular manifestation of chronic hypocalcemia is papilledema, caused by increased pressure of the cerebrospinal fluid, which improves with reversal of hypocalcemia.