Why does my newborn baby have low blood sugar levels?

Some babies are at risk of not having enough glucose, a type of sugar that fuels the brain. Low blood glucose levels in newborns are associated with brain injury and developmental delay. Low levels are more common in certain babies, including those who are unusually large or small at birth, premature, born to diabetic mothers, or not feeding effectively. Some may have had a difficult delivery. They may be irritable, very sleepy, or cold and have a rapid heart rate or abnormal breathing. Treatment may include the use of a sugar gel taken by mouth, establishing effective breastfeeding, or supplementing with extra milk. If those fail, glucose may be given intravenously. Once the baby’s glucose levels are stable and the baby’s issues are resolved, there is generally no need for ongoing supplementation or other treatment.

A) Describing low blood sugar

Glucose, a type of sugar, is the brain’s fuel. A low glucose level in newborns is associated with brain injury and developmental delay (McKinlay 2015).

During the first few hours of life, blood glucose concentrations fall and then increase as the baby’s body starts making and controlling the levels of glucose.

However, some babies are at risk of abnormally low glucose levels (hypoglycemia) for up to 48 hours after birth. They may or may not show signs when this is happening.

Please discuss any concerns with your health-care providers.

B) Babies who are at higher risk of low blood sugar

Babies who have a higher risk of low glucose include those who (Turner 2019; Wight 2021):

  • Are born too small or too large compared to other babies of the same age. 
  • Are a twin who is more than 10% smaller than the sibling.
  • Are born to:
  • Are born premature.
  • Are not breastfeeding effectively.
  • Have had difficult deliveries.
  • Are born by Caesarean birth.
  • Are cold.
  • Suffer from an infection or certain genetic diseases.

C) Signs of low blood sugar

Signs of low blood glucose in a baby include:

  • Irritability, jitteriness, tremor
  • High-pitched crying
  • Excessive sleepiness, listlessness, or weakness
  • Abnormal breathing patterns
  • Being cold
  • Poor or no feeding
  • Rapid heart rate
  • Blue colouring
  • Seizures
  • Not breathing or irregular breathing

Blood glucose levels can be tested in various ways. Most hospitals use blood from the baby’s heel. There is some debate about what constitutes a low glucose level.

D) Treating low blood sugar

Treating low blood glucose may include (Narvey 2019; Weston 2016):

  • The use of dextrose (sugar) gel
  • Giving the baby sugar through a vein (intravenous [IV] glucose)  
  • Admission to the neonatal intensive care unit for close monitoring and treatment

Other measures include:  

If a mother knows her baby will be at risk of low glucose after delivery, she may consider manually expressing colostrum before the baby’s birth. This would be used to supplement the baby if any are needed and may limit the need for infant formula (Wight 2021). Human donor milk can also be used for this purpose (Ponnapakkam 2021).

Once the baby’s glucose levels are normal and the baby’s issues are resolved, low glucose levels are unlikely to cause further problems. Unless your health-care providers tell you otherwise, there is no need for ongoing supplementation or other treatment. If the baby can breastfeed effectively, any supplements can be decreased and then stopped.


McKinlay CJ, Alsweiler JM, Ansell JM, et al. Neonatal Glycemia and Neurodevelopmental Outcomes at 2 Years. N Engl J Med. 2015 Oct 15;373(16):1507-18

Narvey MR, Marks SD. The screening and management of newborns at risk for low blood glucose. Paediatr Child Health. 2019 Dec;24(8):536-554

Ponnapakkam A, Rees D, Gallup MC, et al. Supplementation-based hypoglycemia guidelines including donor breast milk reduce NICU admission. J Perinatol. 2021 May 18

Turner D, Monthé-Drèze C, Cherkerzian S, et al. Maternal obesity and cesarean section delivery: additional risk factors for neonatal hypoglycemia? J Perinatol. 2019 Aug;39(8):1057-1064
Weston PJ, Harris DL, Battin M, et al. Oral dextrose gel for the treatment of hypoglycaemia in newborn infants. Cochrane Database Syst Rev. 2016 May 4;(5):CD011027

Wight NE; Academy of Breastfeeding Medicine. ABM Clinical Protocol #1: Guidelines for Glucose Monitoring and Treatment of Hypoglycemia in Term and Late Preterm Neonates, Revised 2021. Breastfeed Med. 2021 Apr 7