Blood glucose level
blood glucose <40mg/dL (preterm infants repeated levels below <50)
blood glucose <40mg/dL (preterm infants repeated levels below <50)
There is a normal fall in glucose @ 2-4hr of life
If no obvious precipitant, consider workup for inborn errors of metabolism
Neonatal hypoglycemia
Decreased substrate availability
Non-neonatal hypoglycemia 
Intra-uterine growth retardation
Neonatal jaundice
Glycogen storage disease
Neonatal abstinence syndrome
Inborn errors of metabolism 