Hypercalcemia may be a manifestation of a serious disease and malignancy, and may also be discovered accidentally through laboratory tests in patients with no obvious signs of disease. Before analyzing hypercalcemia, it is important to ensure that hypercalcemia is actually present, rather than a false positive result found in laboratory tests. Hypercalcemia is only confirmed when the corrected serum calcium concentration exceeds 10.8 mg/dl (2.7 mmol/L) or the ionized calcium exceeds 5.4 mg/dl (1.35 mmol/L). Since hypercalcemia is always long-term, whether it is persistent or intermittent, it can be confirmed by multiple fasting blood calcium tests. Once hypercalcemia is confirmed, its cause must be diagnosed.