The most common cause of hypercalcemia in the emergency department (ED) is malignancy-associated hypercalcemia (MAH), which can be caused by direct bone resorption from bone metastases, vitamin D secreting malignancies, and increased parathyroid hormone (PTH) or PTH-related protein (PTHrP) levels. Malignancy-associated hypercalcemia is associated with a very poor prognosis, with half of the patients dying within a month of diagnosis. Management consists of adequate hydration, bisphosphonate therapy, and correction of other abnormal electrolyte levels. Currently, no therapies have demonstrated an effect on mortality and are therefore viewed only as a means of stabilizing the patient until the underlying condition can be treated. All MAH patients should receive an oncology consult as soon as possible so they are able to receive treatment for the causative malignancy and increase their chance of survival.