OBJECTIVE Hypercalcaemia is commonly associated with cancer which is usually advanced and portends a poor prognosis. Hypocalcaemia is more often seen as a complication of therapy aimed at reducing skeletal morbidity rather than an effect of the cancer itself. We present an overview of calcium disorders in malignant disease. RESULTS A significant proportion of patients who have a cancer and become hypercalcaemic have an alternative cause for their hypercalcaemia.Evidence for the use of loop diuretics is lacking, and such agents should not be routinely used unless significant volume overload occurs during rehydration. Bisphosphonates are generally established as first-line therapy after volume expansion with saline. As knowledge of bone biology increases, there is interest in the use of the mAb denosumab, for the management refractory hypercalcaemia. Knowledge of the vitamin D status, and supplementation of vitamin D, may reduce the risk of hypocalcaemia when potent antiresorptive medications are being used. CONCLUSIONS Calcium disorders can be predicted in many tumour types and with antiresorptive therapy. A logical approach to prevention and management of these imbalances should be incorporated into cancer patient care.