Serum levels that define hypoglycemia in pre-term or low birth weight infants are:

• A. the same as adults
• B. lower than adults
• C. the same as a normal full-term infant
• D. higher than a normal full-term infant

Answer: (B)

In newborns, especially those who are preterm or of low birth weight, glucose regulation is not fully mature. They have smaller liver glycogen stores and immature gluconeogenesis, and their brains rely on glucose more than adults do. Because their normal, stable glucose range is already lower than that of adults, the level at which we define hypoglycemia is also lower. In other words, what counts as “hypoglycemia” for a preterm or low birth weight infant is a lower serum glucose threshold than in adults. This reflects their physiologic baseline rather than an error in glucose control. Clinically, many healthy term newborns can tolerate glucose values in the 40–60 mg/dL range without immediate harm, but thresholds and treatment decisions are individualized based on symptoms and duration, with preterm infants often monitored closely for even modest drops.