Patients with hypercalcaemia of malignancy present with signs and symptoms of greater severity than those with hypercalcaemia associated with non-malignant causes. Signs and symptoms may be attributed mistakenly to progression of the underlying cancer or the side effects of anti-cancer treatment. Unless treated appropriately, the signs and symptoms of hypercalcaemia of malignancy will progress quickly and ultimately become life-threatening. Rehydration with intravenous fluid followed by intravenous bisphosphonate is often effective in lowering serum calcium levels. However, unless the cancer is amenable to treatment, hypercalcaemia will recur. Even when treated, hypercalcaemia of malignancy is a poor prognostic indicator, with 80% of patients dying within 12 months of the first episode.

This article aims to raise awareness of hypercalcaemia of malignancy by discussing the underlying mechanisms, the associated signs and symptoms, and the need for prompt and appropriate treatment.