A consistent definition for neonatal hypoglycemia in the first 48 h of life continues to elude us. Enhanced understanding of metabolic disturbances and genetic disorders that underlie alterations in postnatal glucose homeostasis has added useful information to understanding transitional hypoglycemia. This growth in knowledge still has not led to what we need to know: "How low is too low and for how long?" This article reviews the current state of understanding of neonatal hypoglycemia and how different approaches reach different "expert" opinions.