Diagnosis of Hypercalcemia Total serum (and sometimes ionized) calcium concentration Chest x-ray; measurement of electrolytes, blood urea nitrogen (BUN), creatinine, phosphate, PTH, alkaline phosphatase, and serum protein immunoelectrophoresis to determine the cause Sometimes urinary excretion of calcium with or without phosphate Hypercalcemia is diagnosed by a serum calcium concentration > 10.4 mg / dL (> 2.60 mmol / L) or ionized serum calcium > 5.2 mg / dL (> 1.30 mmol/L).