Neonatal Hypercalcemia By Kevin C Dysart, MD, Nemours / Alfred I duPont Hospital for Children Reviewed / Revised Mar 2021 | Modified Sep 2022 View Patient Education Etiology Symptoms and Signs Diagnosis Treatment Hypercalcemia is total serum calcium > 12 mg / dL (> 3 mmol / L) or ionized calcium > 6 mg / dL (> 1.5 mmol/L).