Hypercalcemia is elevated serum calcium concentration and is most commonly caused by drugs, malignancy, and primary hyperparathyroidism. Patients present with stones (renal or biliary), bones (bone pain), abdominal moans (abdominal pain, nausea, and vomiting), and psychic groans (decreased concentration, confusion, fatigue, stupor, and coma). Cardiovascular consequences can also ensue, manifesting as cardiac arrhythmias due to a truncated QT interval.

Drug-induced hypercalcemia can be due to excessive drug consumption (vitamin A, vitamin D, or thiazide diuretics). Calcium absorption (or bone resorption) exceeds the excretion of calcium, resulting in excess calcium in the blood. Less commonly associated medications include lithium (due to increased secretion of parathyroid hormone [PTH]), teriparatide, theophylline (mild toxicity via beta-adrenergic regulation), and certain topical ointments.

Non-drug-induced causes are parathyroid disorders, specific malignancies such as solid tumors (commonly lung, breast, ovarian, kidney, and pancreatic primary tumors), carcinomas with or without bone metastases, hematologic cancers (leukemia, lymphoma, myeloma, etc), granulomatous diseases (sarcoidosis, tuberculosis, granulomatosis with polyangiitis, histoplasmosis, coccidioidomycosis, silicosis, berylliosis, Pneumocystis pneumonia, and Nocardia infection), chronic liver disease, renal insufficiency, kidney transplant, bacteriosis, parenteral feeding, and familial hypocalciuric hypercalcemia.

Cancer-associated hypercalcemia may be caused by elevated levels of PTH, PTH-related protein, 1,25-dihydroxyvitamin D, tumor necrosis factor (TNF), interleukin (IL)-6, IL-1, macrophage inhibitory protein, and other mediators. Cancer-associated hypercalcemia has a poor prognosis.

Rare causes include dehydration, pheochromocytoma, acute adrenal insufficiency, Paget disease, Williams syndrome, and prolonged immobilization.