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Understanding Healthcare

Hypoglycemic Reaction (Newborn)

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Blood sugar is also called glucose. The body uses glucose as energy. Before birth, your baby relied on you for glucose. They didn't make their own. After birth, the umbilical cord is cut. Now your newborn baby depends on feedings for glucose. If the first feeding is delayed longer than 3 to 6 hours, a newborn may develop low blood sugar (hypoglycemia). This is a common problem in the first few days of life. It causes a hypoglycemic reaction.

Signs of a hypoglycemic reaction in newborns include:

  • Being irritable, jittery, or shaking (tremors).
  • A high-pitched cry.
  • Feeding problems.
  • Lack of energy (lethargy) or limpness.
  • Skin that is blue in color.
  • Seizures.
  • Very fast breathing or heart rate.
  • Low body temperature, and trouble staying at their body temperature.

Hypoglycemia can also be a sign of infection. Your baby may have tests to make sure they don't have an infection. Hypoglycemia occurs most often in babies born too early (prematurely) or at a low birth weight. It may also occur in babies born to women who have diabetes.

Hypoglycemia is diagnosed in newborns by testing blood. Low blood sugar must be carefully watched to prevent a serious problem. Babies who are premature or too ill to feed will be given nutrition by a tube to the stomach or into a vein. If hypoglycemia lasts, the doctor will test for other causes.


Home care

Your child's doctor may prescribe a special feeding schedule for your baby. Follow the doctor's instructions for feeding.

General care

  • Know your baby's signs of hunger and low blood sugar.
  • Allow time for frequent, quiet feedings. If your baby is not feeding well, talk with your care team about ways that will help.
  • Keep your baby dressed warmly. Newborns have trouble controlling their body temperature. They can get cold easily. Cold may trigger a hypoglycemic reaction. If your baby has a lower body temperature than normal, warm them as soon as possible. Add more layers and a cap to hold in body heat. Remove any damp clothes and replace with warm, dry clothes. Keep your baby away from cold drafts.
  • If you have diabetes and are breastfeeding, watch your glucose levels closely.
  • If told to do so, check your baby's blood sugar as directed.

If symptoms return

Feed your baby breast milk or infant formula. Then contact your baby's doctor.


Follow-up care

Follow up with your baby's doctor or as advised. If lab tests were done, you will be told of any results that may affect your baby's care.


When should you call for help?

Contact the doctor now or seek immediate medical care if:

  • Your baby has a fever higher than 100.4°F (38°C) rectal, or a temperature lower than normal.
  • Your baby's low blood sugar symptoms come back (see symptoms above).

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© 2000-2026 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.

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