Background: The ingestion of large amounts of milk and antacids to treat peptic ulcer disease was a common cause of hypercalcemia in the past (the “milk-alkali syndrome”). The current popularity of calcium and supplements has given rise to a similar problem. Objectives: To evaluate the prevalence and characteristics of hypercalcemia induced by calcium intake (“calcium supplement syndrome”; or CSS) in hospitalized patients. Methods: We conducted a retrospective; electronic health record (EHR)-based review of patients with hypercalcemia over a 3-year period. Diagnosis of CSS was based on the presence of hypercalcemia; a normal parathyroid hormone (PTH) level; renal insufficiency; metabolic alkalosis; a history of calcium intake; and documented improvement with treatment. Results: Of the 72 patients with non-PTH mediated hypercalcemia; 15 (20.8%) satisfied all the criteria for the diagnosis of CSS. Calcium; vitamin D; and multivitamin ingestion were significantly associated with the diagnosis (p values < 0.0001; 0.014; and 0.045 respectively); while the presence of hypertension; diabetes; and renal insufficiency showed a trend towards statistical significance. All patients received intravenous fluids; and six (40%) received calcium-lowering drugs. The calcium level at discharge was normal 12 (80%) of patients. The mean serum creatinine and bicarbonate levels decreased from 2.4 and 35 mg/dL on admission respectively; to 1.6 mg/dL and 25.6 mg/dL at discharge respectively. Conclusion: The widespread use of calcium and vitamin D supplementation can manifest as hypercalcemia and worsening of kidney function in susceptible individuals. Awareness among health care professionals can lead to proper patient education regarding these health risks.