Calcium has both structural and metabolic roles in the body. The exact regulation of calcium in the extracellular fluid is essential to the maintenance of homeostasis and is dependent on parathyroid hormone, calcitonin, and cholecalciferol. Hypercalcemia results in neuromuscular hypoexcitabiltiy and renal dysfunction. Differential diagnoses for hypercalcemia include pseudohyperparathyroidism, osteolytic lesions, tertiary hyperparathyroidism, primary hyperparathyroidism, vitamin D intoxication, and laboratory error. Identification and elimination of the underlying cause is the key to successful management of the hypercalcemic patient.