Hypocalcemia is a frequently observed clinical and laboratory abnormality in neonates. Ionic calcium is crucial for many biochemical processes including blood coagulation, neuromuscular excitability, cell membrane integrity, and many of the cellular enzymatic activities. Healthy term infants undergo a physiological nadir in serum calcium levels by 24-48 h of age. This nadir may drop to hypocalcemic levels in high-risk neonates including infants of diabetic mothers, preterm infants and infants with perinatal asphyxia. The early onset hypocalcemia which presents within 72 h requires treatment with calcium supplementation for at least 72 h. In contrast, late onset hypocalcemia usually presents after 7 days and requires longer term therapy.