Hypercalcemia, also spelled hypercalcaemia, is a high calcium (Ca²⁺) level in the blood serum. The normal range is 2.1–2.6 mmol/L (8.8–10.7 mg/dL, 4.3–5.2 mEq/L), with levels greater than 2.6 mmol/L defined as hypercalcemia. Those with a mild increase that has developed slowly typically have no symptoms. In those with greater levels or rapid onset, symptoms may include abdominal pain, bone pain, confusion, depression, weakness, kidney stones or an abnormal heart rhythm including cardiac arrest.

Most outpatient cases are due to primary hyperparathyroidism and inpatient cases due to cancer. Other causes of hypercalcemia include sarcoidosis, tuberculosis, Paget disease, multiple endocrine neoplasia (MEN), vitamin D toxicity, familial hypocalciuric hypercalcaemia and certain medications such as lithium and hydrochlorothiazide. Diagnosis should generally include either a corrected calcium or ionized calcium level and be confirmed after a week. Specific changes, such as a shortened QT interval and prolonged PR interval, may be seen on an electrocardiogram (ECG).

Treatment may include intravenous fluids, furosemide, calcitonin, intravenous bisphosphonate, in addition to treating the underlying cause. The evidence for furosemide use, however, is poor. In those with very high levels, hospitalization may be required. Haemodialysis may be used in those who do not respond to other treatments. In those with vitamin D toxicity, steroids may be useful. Hypercalcemia is relatively common. Primary hyperparathyroidism occurs in 1–7 per 1,000 people, and hypercalcaemia occurs in about 2.7% of those with cancer.