Hypoglycemia in Premature Babies

A Guide to Low Blood Sugar in Preemies

Nurse tending to newborn in incubator
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Preemies face many challenges. One of the common issues premature babies have to deal with is low blood sugar. When a preemie has low blood sugar, it's called neonatal hypoglycemia.

Blood sugar is the amount of sugar, or glucose, that circulates in the blood. Blood sugar is important because the body and the brain use glucose for energy and growth. If the level of sugar in the blood is too low for too long, it can be dangerous.

What Is a Low Blood Sugar in Premature Babies?

When the blood glucose level falls below 40 mg/dl, it's often considered a low blood sugar or hypoglycemia. However, doctors, hospitals, and experts do not all agree on the specific number a blood sugar should be before it's called hypoglycemia and needs treatment. Therefore, the number alone does not define a low blood sugar. Other factors such as the gestational age of the child, how long it's been since the baby was born, and the child's symptoms are also taken into account when deciding the diagnosis and treatment of low blood sugar in premature infants. Here are the general guidelines for neonatal hypoglycemia based on the laboratory results of a plasma glucose test.

A premature baby born between 34 and 37 weeks:

  • Any baby with any symptoms: below 40 mg/dl
  • From birth to 4 hours of age without symptoms: below 40 mg/dl
  • From 4 hours of age to 24 hours of age without symptoms: below 45 mg/dl

    A premature baby born before 34 weeks gestation:

    • Although there isn't a specific guideline for preemies born before 34 weeks, hypoglycemia may be considered with a blood glucose below 45 mg/dl (the range may be between 40 mg/dl- 50 mg/dl).

    Preemies and Hypoglycemia

    During pregnancy, a mother passes sugar to her baby.

    Towards the end of the pregnancy, the baby will store some of that sugar to use in the days after birth. When full-term newborns use up their stored glucose, they can get more by breastfeeding or taking a bottle. Regular feedings of breast milk or infant formula provide full-term newborns with what they need to maintain a healthy blood sugar level.

    But, when a baby is born too early, the amount of sugar built up and stored is much lower than if the baby was born at full-term. Plus, many preemies are not able to take in nutrients through feedings right away. That puts premature babies at a greater risk of developing low blood sugar in the hours and days after they're born.

    The Causes of Low Blood Sugar in Preemies

    The sugar that babies store up before they're born can be found in the liver. Since preemies have an immature liver, they don't have the same amount of stored up glucose as full-term babies. A premature baby can quickly use up the little sugar that's been stored and develop hypoglycemia if:

    The Signs and Symptoms of Neonatal Hypoglycemia

    Sometimes there aren't any signs or symptoms of low blood sugar. But, when symptoms are noticeable, they may include:

    • Jitters and tremors
    • Lethargy (weakness and low energy)
    • Poor muscle tone
    • Respiratory distress
    • A pale or bluish skin color
    • Low body temperature
    • Poor sucking and feeding
    • A weak or high-pitched cry

    Since many of these signs and symptoms are also associated with prematurity and other newborn conditions, it's difficult to tell if they're from low blood sugar or something else.

    That's one of the reasons it's so important to screen all babies who may be at risk.

    Testing for Low Blood Sugar

    Doctors check blood sugar levels by testing the blood. To screen your child for hypoglycemia, a nurse will often take a drop of blood from the side of your baby's heel and place it on a test strip in a bedside blood glucose monitor. Bedside glucometers are an excellent tool for screening, but the result is not as accurate as a laboratory result. So, if the glucose monitor shows a low blood sugar level, it must be verified as quickly as possible. Another blood sample will be drawn directly from your child's vein or a line already attached to the baby such as an umbilical catheter or a PICC line. It will be placed in a blood collection vial and sent to the laboratory for confirmation.

    How Often Are Preemies Tested for Low Blood Sugar?

    When your baby first arrives in the NICU or special care unit, a blood sugar test may be taken right away and then as often as every two hours. If your child can take feedings, blood sugar is often checked before each feeding. Once the blood sugar levels are stable, the testing will occur less often. And, of course, any baby that shows symptoms of hypoglycemia will be tested right away.

    Is Hypoglycemia Dangerous?

    Most of the time, hypoglycemia is a temporary condition that lasts only a few days or weeks. It is usually caught and treated before it becomes dangerous. However, there are some rare hormonal and genetic issues a baby can be born with that can cause long-term low blood sugar issues. If it is not treated for a long time, low levels of blood sugar can cause serious problems that lead to brain damage, learning disabilities, seizures, vision problems, and cerebral palsy.

    The Treatment of Hypoglycemia in Premature Infants

    When it comes to hypoglycemia, every baby is treated individually. Doctors decide on how to handle each case depending on what the blood sugar level is, how early the child was born, the symptoms, and the child's overall health.

    Here are some of the ways doctors treat low blood sugar in preemies:

    • If a child can tolerate feedings, he can breastfeed, take a bottle, or have a tube feeding (breast milk or preemie formula is put through a small, flexible, straw-like tube that goes from the nose or mouth into the stomach). The sugar in the breast milk or the formula may be all the baby needs to bring the blood sugar level up.
    • The baby may need an intravenous line (IV) to receive fluids containing extra sugar. The extra sugar goes directly into the baby's blood.
    • If it's necessary, there are medications such as steroids that can be given to a baby to increase the sugar levels.
    • In rarer, more severe cases, a baby may need surgery. The pancreas is an organ that makes the hormone insulin and regulates blood sugar levels in the body. But, if there is too much insulin, the removal of part or all of the pancreas may be needed.

    A Word From Verywell

    It can be scary and overwhelming to hear that your child has hypoglycemia or any other medical condition for that matter. But, hypoglycemia is one of the common issues that premature babies face. Thankfully, since there is ongoing monitoring and testing in the NICU and special care area, low blood sugar in preemies is usually identified and treated very quickly.

    If your child has a mild case of low blood sugar in the NICU that is treated right away, it shouldn't lead to any future problems. Once you take your baby home and she's eating well, hypoglycemia should not return. If your baby is born with a health condition that leads to long-term issues with hypoglycemia, it will be a little more challenging, but it will be okay. You will learn how to care for your child, and your baby will continue to receive follow-up care and treatment after you leave the hospital.


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