What are the symptoms of hypocalcemia (low calcium)?

Symptoms of Hypocalcemia

Hypocalcemia causes neuromuscular irritability as its hallmark manifestation, ranging from mild paresthesias and muscle cramps to life-threatening tetany, seizures, and cardiac arrhythmias. 1

Neuromuscular Symptoms

The most characteristic symptoms involve neuromuscular irritability:

• Paresthesias (tingling/numbness) affecting the hands, feet, and perioral (around the mouth) region are among the most common early symptoms 1, 2
• Muscle cramps and spasms occur frequently and can range from mild to severe 1, 2
• Tetany represents the classic severe manifestation, characterized by focal or generalized tonic muscle contractions 2, 3
• Laryngospasm can occur in severe cases, representing a potentially life-threatening complication 2

Neurological and Psychiatric Symptoms

Hypocalcemia affects the central nervous system in multiple ways:

• Seizures may be the first presenting sign, particularly in patients with underlying seizure disorders 1
• Irritability and emotional changes are common neurological manifestations 1
• Confusion or altered mental status can develop with severe hypocalcemia 1
• Behavioral changes including anxiety or depression may occur, and these psychiatric symptoms can lead to misdiagnosis if calcium levels are not checked 1, 4
• Fatigue is a frequent but nonspecific complaint 1

Cardiovascular Manifestations

Cardiac involvement can be serious:

• Prolonged QT interval on electrocardiogram is the most common cardiovascular finding 1, 2
• Cardiac arrhythmias including ventricular tachycardia and fibrillation can occur 1
• Cardiomyopathy rarely develops as a complication of chronic hypocalcemia 1
• Myocardial dysfunction may manifest in acute severe cases 2

Severity Spectrum

The clinical presentation varies dramatically based on severity and acuity:

• Mild hypocalcemia may present with only circumoral numbness and mild paresthesias of the extremities 2
• Moderate hypocalcemia typically causes more pronounced muscle cramps and neuromuscular irritability 1
• Severe acute hypocalcemia (ionized calcium <0.75 mmol/L) manifests with tetany, seizures, and potential cardiac complications 2, 3

Important Clinical Pitfalls

Several critical considerations can prevent missed or delayed diagnosis:

• Symptoms may be subtle and easily confused with psychiatric conditions such as anxiety or depression, leading to misdiagnosis if calcium levels are not measured 1, 4
• Symptoms can emerge at any age in patients with underlying parathyroid dysfunction, even without prior history of hypocalcemia 4
• Biological stress including surgery, childbirth, infection, acute illness, puberty, and pregnancy can precipitate symptomatic hypocalcemia in previously asymptomatic patients 1, 4
• Perioperative periods represent particularly vulnerable times, with post-thyroid or parathyroid surgery being the most common setting for acute hypocalcemia 2
• Lifestyle factors such as alcohol consumption and carbonated beverage intake (especially colas) can worsen hypocalcemia 1, 4

Diagnostic Approach

When hypocalcemia is suspected based on symptoms:

• Measure pH-corrected ionized calcium as this is the most accurate test 1, 4
• Check magnesium levels in all hypocalcemic patients, as hypomagnesemia impairs PTH secretion and must be corrected first 1, 4
• Assess parathyroid hormone (PTH) levels to determine if hypoparathyroidism is present 1
• Monitor for prolonged QT interval on ECG, especially in symptomatic patients 1, 2