Symptoms and signs

• Unusual unless calcium (Ca²⁺) >3.0 mmol/L
• GI: nausea, vomiting, constipation, abdominal pain
• Renal: polyuria, polydipsia
• CVS: hypertension, on ECG: altered QT interval, long PR, wide QRS, arrhythmias
• CNS: various including depression, cognitive difficulties, headache, altered consciousness, acute psychosis

Investigations

• Adjusted Ca²⁺ [aCa²⁺], albumin, PTH (EDTA), alkaline phosphatase, phosphate
• A broad estimate of adjusted calcium is given by: serum unadjusted Ca²⁺ + 0.02 (40 - albumin g/L) mmol/L
• Chase lab for urgent PTH result
• U&Es, creatinine, glucose, myeloma screen
• FBC, ESR
• Chest x-ray and ECG

• Reduce aCa²⁺
• Stop thiazides and any vitamin A, D or Ca²⁺ supplements
• For guidance follow Initial management and then Response to treatment flowcharts
• Treat the underlying cause.

• Check PTH and assess if PTH-driven hypercalcaemia or PTH-suppressed hypercalcaemia. (Most obviously hyperparathyroidism if PTH above upper limit of reference range but insufficiently suppressed PTH is sometimes seen)
• If PTH >1.5 pmol/L, consider Primary hyperparathyroidism or Familial hypocalciuric hypercalcaemia. CKD patients may have tertiary hyperparathyroidism
• Contact endocrinology team for advice if hyperparathyroidism. Contact renal team for advice if AKI or CKD
• If PTH ≤1.5 pmol/L, consider: malignancy (lung, breast, haematological rarely); granulomatous disease; AKI or adrenal insufficiency; excess Vitamin D/Ca²⁺ intake; drug therapy (e.g. lithium, oestrogens, progestogens, tamoxifen).
• Contact oncologists if evidence of malignancy, unless haematological, in which case contact haematologists
• If treatable, treat underlying cause as soon as possible
• If cause not treatable, ensure hydration maintained because this will work, whatever the cause, even if only by dilution