Always look at the corrected calcium (it should be adjusted for the serum albumin concentration)
Can be inaccurate in extreme albumin concentrations, paraproteinaemia or acidosis. There is an excellent two page summary from the British Society of Endocrinology which is incredibly useful & provides clear guidelines.

Classification:
  • Mild (2.65 – 3.00 mmol/L): Patient usually asymptomatic
  • Moderate (3.01-3.40 mmol/L): Can be asymptomatic or symptomatic
  • Severe (>3.40 mmol/L): Risk of dysrhythmia and coma
Causes:
  • 90%: Primary hyperparathyroidism or malignancy
  • Medications: Thiazide diuretics, Lithium, Theophylline toxicity
  • Familial hypocalciuric hypercalcaemia
  • Non-malignant granulomatous disease
  • Thyrotoxicosis
  • Tertiary hyperparathyroidism
  • Rhabdomyolysis
  • Immobilisation
  • Adrenal insufficiency
  • Milk-alkali syndrome
  • Hypervitaminosis A
  • Phaeochromocytoma
When asked to review a patient with hypercalcaemia
  • History: Ask patient about
    • Symptoms of hypercalcaemia: Polyuria, polydipsia, loss of appetite, nausea, constipation, mood disturbance, cognitive impairment, confusion
    • Symptoms of underlying causes: Weight loss, night sweats, cough, bleeding etc
  • Examination
    • Assess for cognitive impairment / GCS
    • Fluid balance status
    • Any specific examination if appropriate for underlying cause e.g. lymph nodes, abdomen etc
  • Tests
    • ECG: Shortened QT interval / other conduction abnormalities
    • Bloods: Corrected calcium, Phosphate, PTH, U&Es
  • Management
    • You should always discuss patients with hypercalcaemia with a senior
    • See local policy & the above guides from the Society of Endocrinology. Usually you are giving IV 0.9% sodium chloride 4-6L in 24 hours therefore fluid balance monitoring is required via catheter & regular reviews
    • Further treatment (again discussed in the guide above) includes IV bisophosphonate which can take some time to work & require a well hydrated patient. 
    • There is also further specialist management which would definitely require specialty input 
      • If lymphoma / other granulomatous diseases / vitamin D poisoning: Oral high dose Prednisolone
      • If poor response to above measures, can consider (under specialist supervisor) Calcimemetics, denosumab, calcitonin), parathyroidectomy
References / Further Reading
Walsh J, Gittoes N, Selby P, the Society for Endocrinology Clinical Committee. Emergency management of acute hypercalcaemia in adult patients. Society for Endocrinology Endocrine Emergency Guidance. 2016. http://www.endocrineconnections.org DOI: 10.1530/ec-16-0055
National Institute for Health and Care Excellence. Hypercalcaemia. Retrieved from https://cks.nice.org.uk/hypercalcaemia#!diagnosisSub:1

By Angela Yan FY2