What initial investigations should I perform for a patient presenting with hypercalcaemia?

For a patient presenting with hypercalcaemia, the initial investigations should include:

• Measurement of albumin-adjusted serum calcium to confirm hypercalcaemia and assess severity. Repeat the measurement at least once if the initial level is ≥2.6 mmol/L or ≥2.5 mmol/L with features suggestive of primary hyperparathyroidism.
• Measurement of parathyroid hormone (PTH) concurrently with albumin-adjusted serum calcium if the calcium level is ≥2.6 mmol/L on at least two occasions or ≥2.5 mmol/L with suspicion of primary hyperparathyroidism.
• Review of medications that may cause hypercalcaemia, such as thiazide diuretics or lithium, with consideration to stop and recheck calcium after 3 weeks if applicable.
• Assessment for reversible causes including excess intake of calcium, vitamin D, or vitamin A.

Following these initial tests, if primary hyperparathyroidism is suspected, further investigations such as vitamin D measurement and 24-hour urine calcium excretion or calcium:creatinine clearance ratio may be performed in secondary care to differentiate from familial hypocalciuric hypercalcaemia.

Additional investigations to assess complications and underlying causes may include renal imaging (ultrasound, X-ray, or CT) to detect renal stones or nephrocalcinosis, bone mineral density measurement by DXA scan, and urinary biochemical stone profile.

Referral to an appropriate specialist is recommended unless a reversible cause is identified and corrected normalizing calcium levels.

Emergency admission is indicated for severe hypercalcaemia (corrected calcium >3.5 mmol/L) or severe symptoms for urgent specialist management.

These recommendations are based on NICE guidelines NG132 and CKS Hypercalcaemia guidance.

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