Hypoglycemia is the medical term for low blood sugar. In newborns, hypoglycemia is common immediately after birth, but it usually corrects itself when the infant begins feeding regularly.

Doctors usually detect hypoglycemia when the infant is still in the hospital. They do not send infants with hypoglycemia home until their blood sugar is stable.

Sometimes, however, hypoglycemia may persist or come back. If hypoglycemia occurs after the first 48 hours following birth, it may be a sign of an underlying condition.

Hypoglycemia in a newborn is treatable. However, without treatment, this medical condition can cause lasting damage. Parents and caregivers who notice symptoms of hypoglycemia must act quickly. A doctor may recommend giving sugar gel, providing more regular feeds, or supplementing breast milk with formula.

In this article, learn about the signs of hypoglycemia in a newborn. This article also covers causes, treatments, and prevention.

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Not all infants with hypoglycemia have symptoms, especially in the early stages. For this reason, many hospitals and birth centers test blood glucose at birth for infants who are at risk and at regular intervals thereafter.

Most doctors consider blood glucose that is below 47 milligrams per deciliter (mg/dl) to be the definition of hypoglycemia in newborns.

When an infant has symptoms, a parent or caregiver may notice:

  • shakiness
  • blue or white discoloration of the lips and skin
  • a lack of interest in eating
  • weak or floppy muscles
  • low energy
  • low body temperature
  • seizures

Hypoglycemia may be more severe if blood glucose continues dropping or remains low for 3 or more days.

It is common for infants to temporarily have hypoglycemia immediately after birth. If this happens, a doctor will monitor their blood glucose to see if it returns to normal. If it does, treatment may not be necessary.

However, if an infant is showing signs of hypoglycemia in the days, weeks, or months after birth, call a doctor right away.

The doctor may advise giving breast milk, formula, or a mixture of glucose and water, if a person has any, to try to raise the infant’s blood sugar levels. They may also recommend visiting a health center to get a blood glucose test.

The symptoms of hypoglycemia in newborns are similar to those of many other conditions, so it is important to get help from a healthcare professional.

Prompt feeding at birth and ongoing, on-demand feeding can reduce the risk of hypoglycemia by ensuring that an infant gets adequate nutrition. If someone is nursing, frequent feeding also helps ensure adequate breast milk supply.

There are several reasons that a newborn might develop hypoglycemia. These include the following.

Transitional hypoglycemia

A drop in blood glucose is a normal part of the transition to life outside of the uterus. This is known as transitional hypoglycemia. As long as this drop is temporary and mild, it does not typically harm the infant.

Transitional hypoglycemia occurs because, inside the uterus, a fetus gets its nutrients from the placenta via the umbilical cord. Just after birth, healthcare professionals clamp and then cut the cord, stopping the infant’s usual supply of glucose. Usually, transitional hypoglycemia corrects itself quickly when the infant starts feeding regularly.

In some infants, however, this drop is too large, causing dangerously low blood glucose.

Inadequate food

Some infants do not get enough food at birth. This can happen when there are feeding delays, when a parent or caregiver does not feed early or on demand, or when there are issues with breast milk supply.

Medical conditions

There are a variety of medical conditions that can cause difficulty feeding in newborns or difficulty absorbing and storing energy. This can be a cause of persistent hypoglycemia.

Some examples of conditions that may cause or raise the likelihood of this include:

  • congenital hyperinsulinism
  • hypothyroidism
  • galactosemia
  • fructose intolerance
  • Beckwith-Wiedemann syndrome
  • Soto syndrome
  • Costello syndrome

Antenatal steroids

According to a 2020 study, hypoglycemia is a common side effect of the steroid medication betamethasone. Sometimes, doctors give a single course of this drug to pregnant people who are at risk of preterm birth, as it speeds up fetal lung development.

The study found that delayed cord clamping could offer some protection against this side effect in late preterm infants.

A newborn is more likely to develop hypoglycemia if they have one of the following characteristics.

Large size at birth

Infants who are large for their gestational age have higher metabolic and glucose needs. This can raise the likelihood of hypoglycemia, as they may not get as much glucose as they need from breastmilk or formula.

Infants of birthing parents with diabetes are more likely to be large for their gestational age.

Small size at birth

Infants who are small for their gestational age have fewer fat stores and less glycogen storage. This means that they are less able to produce glucose and are more likely to become hypoglycemic, especially if there are other issues, such as delayed feeding.

Prematurity

Premature babies have similar issues to small infants. They may not produce enough glucose. They may also experience difficulty nursing or issues with a breast milk supply.

Hypoglycemia is especially common in late preterm infants, which are infants born between 34 and 36.6 weeks.

Complications during delivery

Infants who experience perinatal stress — which includes birth complications such as fetal distress, eclampsia, or hypothermia — are more at risk of hypoglycemia. This is because they have higher energy needs.

Infants who undergo this kind of stress can temporarily develop high levels of insulin, resulting in a tendency for low blood sugar that may last days or weeks.

If blood glucose falls below 40 mg/dl in the first 4 hours of life or 45 mg/dl in the first 4–24 hours, a doctor may recommend increasing the frequency of feeds to raise blood glucose.

In many cases, it is possible to do this with breast milk. Sometimes, donor milk is also available. Donor milk is breast milk from someone other than the birthing parent.

However, if it is not possible to feed more often with breast milk, a doctor may suggest formula supplementation.

One challenge of giving formula shortly after birth is that it may affect lactation. This can mean that people who want to nurse exclusively are reluctant to supplement with formula.

One 2021 review states that doctors are increasingly recommending starting with an oral sugar gel to improve blood glucose levels in newborns, as some evidence suggests that this does not affect lactation.

If hypoglycemia is severe or does not respond to oral sugar gel, a doctor may recommend IV glucose. Infants with very low blood glucose may need to stay in the neonatal intensive care unit for monitoring.

Hypoglycemia means that an infant does not have enough sugar in their blood to provide adequate energy to fuel their body or brain. There is ongoing scientific debate about the precise level at which this is likely to cause harm.

Transient hypoglycemia that resolves quickly is unlikely to be harmful. However, hypoglycemia that is severe and sustained or that remains untreated may cause serious complications. These include:

  • developmental problems
  • brain damage
  • seizures
  • death

Transitional hypoglycemia is normal immediately after birth, but certain practices can reduce the risk of hypoglycemia becoming a more persistent problem. These include:

  • identifying infants who are at risk of hypoglycemia early
  • immediate feeding within the first hour after birth
  • glucose testing 30 minutes after the first feed for at-risk infants
  • early supplementation for infants with feeding difficulties

Glucose testing after birth will not prevent hypoglycemia, but it can detect the condition early, allowing treatment to start as soon as possible. This reduces the chance that it will cause harm.

Hypoglycemia in newborns is common and, immediately after birth, temporary. However, persistent or severe hypoglycemia is very serious. Prompt treatment can save an infant’s life. If a newborn is showing potential signs of hypoglycemia, call a doctor right away.

Hypoglycemia in newborns can be scary, but the condition is treatable. Parents and caregivers who want to feed exclusively with breast milk may wonder about the risks and benefits of supplementing with formula, including whether and when formula is necessary.

It is important to discuss this and other options, such as donor milk or sugar gels, with a doctor.