GPAtlas🧭 When to suspect
Hypocalcaemia is a low albumin-adjusted (corrected) serum calcium – below the UK reference range of 2.20–2.60 mmol/L. Roughly 45% of circulating calcium is protein-bound, so always interpret the adjusted value with a concurrent albumin; a low albumin will otherwise mimic a hypocalcaemia that is not there.
Suspect it in anyone with neuromuscular excitability – perioral or digital paraesthesia, muscle cramps, or carpopedal spasm – and in the higher-risk groups: recent thyroid or parathyroid surgery (the commonest cause of acute hypocalcaemia), vitamin D deficiency (the commonest cause overall), chronic kidney disease, malabsorption, and long-term proton pump inhibitor (PPI) use (through hypomagnesaemia). Chronic, slowly-developing hypocalcaemia is frequently non-specific (fatigue, low mood, "brain fog") or asymptomatic, whereas an acute fall can precipitate tetany, seizures, laryngospasm or arrhythmia.
The two priorities in primary care are to confirm true (adjusted) hypocalcaemia and grade its severity, and to never miss the severe or symptomatic patient who needs emergency treatment.
| Adjusted calcium | Severity | Action |
|---|---|---|
| ≥ 2.20 mmol/L | Normal | No treatment – investigate only if borderline or symptomatic |
| 1.90–2.19 mmol/L | Mild–moderate (if asymptomatic) | Investigate and treat the cause; oral replacement; recheck |
| < 1.90 mmol/L or symptomatic at any level | Severe | Medical emergency – intravenous (IV) calcium and urgent admission |
Source: Society for Endocrinology
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