Low blood sugar - newborns

Definition

A low blood sugar level in newborn babies is also called neonatal hypoglycemia. It refers to low blood sugar (glucose) in the first few days after birth.

Alternative Names

Neonatal hypoglycemia

Causes

Babies need blood sugar (glucose) for energy. Most of that glucose is used by the brain.

The baby gets glucose from the mother through the placenta before birth. After birth, the baby gets glucose from the mother through her milk, or from formula. The baby can also produce some glucose in the liver.

The glucose level can drop if:

  • There is too much insulin in the blood. Insulin is a hormone that moves glucose from the blood into tissues.
  • The baby is not able to produce enough glucose.
  • The baby's body is using more glucose than is being produced.
  • The baby is not able to take in enough glucose by feeding.

Neonatal hypoglycemia occurs when the glucose level of a newborn causes symptoms or is below the range considered safe for the baby's age. It occurs in about 1 to 3 out of every 1000 births.

Low blood sugar level is more likely in infants with one or more of these risk factors:

  • Born early, has a serious infection, and/or needed oxygen right after delivery
  • Mother has diabetes
  • Slower than expected growth in the womb during pregnancy
  • Smaller or larger in size than expected for their gestational age

Symptoms

Infants with low blood sugar may not have symptoms. If your baby has one of the risk factors for low blood sugar, nurses in the hospital will check your baby's blood sugar level, even if there are no symptoms.

Also, the blood sugar level is usually checked for babies with these symptoms:

Exams and Tests

Newborns at risk for hypoglycemia should have a blood test to measure blood sugar levels frequently after birth. This will be done using a heel stick. The health care provider should continue taking blood tests until the baby's glucose level stays normal for about 12 to 24 hours.

Other possible tests include newborn screening for metabolic disorders, such as blood and urine tests.

Treatment

Infants with a low blood sugar level will need to receive extra feedings with mother's milk or formula. Babies who are breast-fed may need to receive extra formula if the mother is not able to produce enough milk. (Hand expression and massage can help mothers express more milk.) A sugar gel may be given by mouth temporarily if there is not enough milk.

The infant may need a sugar solution given through a vein (intravenously) if unable to eat by mouth, if the blood sugar does not improve with feeding, or if the blood sugar level is very low.

Treatment will be continued until the baby can maintain their blood sugar level. This may take hours or days. Infants who were born early or at a low weight, whose mothers had diabetes, or who have other complications/problems may need to be treated for a longer period of time.

If the low blood sugar continues, in rare cases, the baby may also receive medicine to increase their blood sugar level.

Outlook (Prognosis)

The outlook is good for newborns who do not have symptoms, or who respond well to treatment. However, low blood sugar level can return in a small number of babies after treatment, so levels will be checked after treatment has stopped.

The condition is more likely to return when babies are taken off fluids given through a vein before they are fully ready to eat by mouth.

Very severe or prolonged low blood sugar levels can cause long-term problems with brain development. This is more often true for babies who are at a lower-than-average weight, whose mothers had diabetes, or who have other complications/problems.

Possible Complications

Severe or persistent low blood sugar level may affect the baby's mental function. In rare cases, heart failure or seizures may occur. However, these problems may also be due to the underlying cause of the low blood sugar, rather than a result of the low blood sugar itself.

Prevention

If you have diabetes during pregnancy, work with your provider to control your blood sugar level. Be sure that your newborn's blood sugar level is monitored after birth.

References

Davis SN, Lamos EM. Hypoglycemia and hypoglycemic syndromes. In: Robertson P, ed. DeGroot's Endocrinology. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 38.

Garg M, Devaskar SU. Disorders of carbohydrate metabolism in the neonate. In: Martin RJ, Fanaroff AA, eds. Fanaroff and Martin's Neonatal-Perinatal Medicine: Diseases of the Fetus and Infant. 12th ed. Philadelphia, PA: Elsevier; 2025:chap 90.

Sperling MA. Hypoglycemia. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 111.

Review Date: 12/31/2023
Reviewed By: Mary J. Terrell, MD, IBCLC, Neonatologist, Cape Fear Valley Medical Center, Fayetteville, NC. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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