Inclusion Criteria:  Infants (post-menstrual age ≥ 26 weeks) delivered by Cesarean section or vaginal delivery. Diagnosed to have hyperbilirubinemia:  Hyperbilirubinemia is defined as:  for term and near-term neonates (neonates less than 35 weeks' gestation): Serum Total Bilirubin (STB) level that would qualify for phototherapy requirement as described in American Academy of Pediatrics 2004's guidelines or absolute STB level L 15 mg/dL; for preterm neonates (< 35 weeks' gestation): STB level > 1% of body weight  Exclusion Criteria:  Infants less than 26 weeks postmenstrual age Allergy to zinc sulfate Any reaction seen after administration of first dose of zinc sulfate. Any contraindication to oral medication Infants with a history of taking phenobarbital by their mother