Purpose of Review <p>To provide the reader with understanding of neonatal physiology relating to fluids and electrolytes, and how optimal enteral and parenteral fluid provision should be provided during the transition from intra- to extrauterine life and during management of the various disorders that may occur in the neonatal period.</p> Recent Findings <p>Traditional recommendations of parenteral fluid volumes for late preterm and term infants may overestimate their fluid needs, placing them at risk for overhydration reflected by inadequate postnatal weight loss and hyponatremia. Preterm infants require larger parenteral fluid volumes than those born at term, due to their greater insensible water loss and high urine output related to their inability to adequately concentrate urine. However, care must be taken not to provide excessive fluids as it increases their risk of morbidity, mortality and adverse developmental outcomes.</p> Summary <p>When providing neonates with fluids and electrolytes the uniqueness of their physiology needs to be considered. Meticulous monitoring of serum sodium, body weight and fluid balance is needed to optimize fluid and electrolyte management, especially in extremely preterm and sick infants. The volume and composition of fluid given must be adequate to maintain body homeostasis, but excessive fluid administration increases the risk of adverse neonatal outcomes.</p>