Low Blood Sugar in Newborns

Low blood sugar, or hypoglycemia, is the most common metabolic problem in newborns. Numerous maternal and newborn conditions, from mild to life threatening, can cause hypoglycemia by affecting a baby’s ability to maintain a stable blood sugar level. Early detection and treatment is important to avoid potential immediate and long-term complications.

Newborn Glucose Metabolism

During pregnancy the fetus receives sugar in the form of glucose from the mother via the placenta. The fetus also produces insulin to control its own blood glucose level, potentially in increased amounts if the mother is diabetic. Some glucose is stored in the baby’s liver and muscles late in pregnancy to be available after delivery for energy, according to the Children’s Hospital Boston. These stores are rapidly depleted and must be replenished quickly to support the newborn’s energy needs and brain function.

Newborn Glucose Levels


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The range of newborn blood sugar levels can normally be quite broad, and laboratory measurements are performed mainly to ensure levels are not too low. Although the exact level considered hypoglycemic varies slightly with a baby’s condition and the lab performing the test, a blood glucose level below 40 mg/dL is considered abnormally low, and a level below 20 mg/dL indicates need for aggressive treatment, according to the Stanford School of Medicine.

Causes of Hypoglycemia

Hypoglycemia affects up to 3 out of every 1,000 newborns and is associated with numerous risk factors, Children’s Hospital Boston states. A mother with diabetes, with a serious infection near the time of delivery or who is malnourished increases the baby’s risk of developing low blood sugar. Hypoglycemia also is more likely if the baby is born with a serious infection, hypothyroidism, birth defect or metabolic disorder, or if a baby has experienced abnormal growth during pregnancy, is premature or has suffered oxygen lack during or right after delivery. All of these conditions interfere in some way with the baby’s ability to store or utilize glucose normally.



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Hypoglycemic newborns don’t always show symptoms of low blood sugar, which include:

  • breathing problems
  • blue discoloration
  • weak or jittery movements
  • poor eating
  • a low body temperature

If the baby does exhibit symptoms, or has known risk factors for hypoglycemia, blood sugar levels are measured shortly after birth and at regular intervals thereafter for monitoring purposes. A drop of blood is usually obtained from the heel with a small lancet for the test, but an easily accessible vein or a catheter at the site of umbilical cord attachment can also be used.

Treatment and Prognosis

When blood glucose levels drop below 40 mg/dL, the baby should immediately be breast fed or given formula. The glucose level is rechecked after 30 minutes and if still low either additional feeding or intravenous fluids with sugar will be given. A blood glucose level below 20 mg/dL requires immediate IV fluids, according to MedHelp.org. Treatment might be required for a few hours to a week, after which medications or more aggressive therapy could be tried if the hypoglycemia has not resolved. Prolonged or severe hypoglycemia can lead to seizures, brain injury or developmental delays if not properly treated.