The transition from fetal to neonatal life requires metabolic adaptation to ensure that energy supply to vital organs and systems is maintained after separation from the placental circulation. Under normal conditions, this is achieved through the mobilization and use of alternative cerebral fuels (fatty acids, ketone bodies, and lactate) when blood glucose concentration falls. Severe hypoxia–ischaemia is associated with impaired metabolic adaptation, and animal and human data suggest that levels of hypoglycaemia that are tolerated under normal conditions can be harmful in association with hypoxia–ischaemia. The optimal target blood glucose level for ensuring adequate energy provision in hypoxic–ischaemic encephalopathy (HIE) remains unknown. However, recent data support guidance to maintain a blood glucose concentration of 2.5mmol/L or more in neonates with signs of acute neurological dysfunction, which includes those with HIE, and this is higher than the accepted threshold of 2mmol/L in infants without signs of neurological dysfunction or hyperinsulinism.