Glucose levels are typically lower for newborn babies, with infants regularly having blood sugars as low as 25 mg/dL at birth and rising a few days later. Infants can be born with neonatal hypoglycemia and hyperglycemia.

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Blood glucose levels vary over time, and recommendations can differ as you age.

These recommendations are particularly different for newborn babies, especially if their biological mother has gestational diabetes or has existing diabetes during pregnancy and labor.

This article will explain what glucose levels should be for newborn babies and describe how new parents can be aware of neonatal low and high blood sugars that might develop.

Newborn babies can have lower blood glucose levels than older children, adolescents, and adults. It can depend on many different factors, including age:

  • When your newborn baby is just 1 to 2 hours old, their normal blood glucose levels can be as low as 25 mg/dL or as high as 110 mg/dL.
  • Within the first few days after delivery, their blood sugars will rise to adult levels — 60 to around 100 milligrams per deciliter (mg/dL).
  • During the neonatal period, the first 4 weeks, newborns should generally have glucose levels between 70 and 150 mg/dL.

This is because when babies are in utero, they get all of their nutrients and glucose from their mothers via their placenta and umbilical cord. Some of these nutrients and glucose are stored to use as energy for birth and for the first few days until they have latched for breastfeeding or are taking formula.

Formula, breast milk, or both then become the main source of energy and glucose for your baby until they start eating and drinking other foods and beverages at around 6 months of age. Your baby’s body quickly learns how to store glucose from their formula, breast milk, or both to prevent low blood sugar levels between feeds after the first few days of life.

About “normal” blood sugars

You can read more about what’s considered a normal blood sugar range, which varies across your life span and depends on many factors. Those other factors may include the type of diabetes you have and your age, lifestyle, activity level, hypoglycemic unawareness, and personal health goals.

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Yes. Newborns can be born with what’s called neonatal hypoglycemia, which is lower-than-normal (for even newborns) blood glucose levels at birth.

Although researchers are familiar with transitional low blood sugar levels as babies adapt to life outside of the womb, there are lower than the normal low blood sugars that babies are typically born with. Those glucose levels may be:

  • 30 mg/dL or less within the first 24 hours of life
  • 45 mg/dL or less in the first few days of life

The causes of neonatal hypoglycemia at birth vary but may include:

  • not enough glucose supply at birth
  • depleted fat stores
  • poor mechanisms of glucose production in your baby’s body
  • increased glucose use, often caused by too much insulin production in utero
  • increased metabolism or metabolic demand
  • pituitary gland or adrenal failure

Low blood sugar at birth is seen most commonly in the following groups:

  • later-preterm babies (34 to 36 weeks and 6 days)
  • large for gestational-age babies
  • small for gestational-age babies
  • infants of diabetic mothers

Preterm and small gestational-age babies are at risk due to their low glycogen stores, lower adipose tissue (or body fat), and increased metabolic demands (relative to their body weight) because of their large brain size.

On the other hand, large gestational-age babies and babies of women who had diabetes during pregnancy may experience hyperinsulinism and increased glucose use. This puts them at risk of low blood sugars upon birth and in the postnatal period. This is because, in utero, the fetal glucose concentrations are proportional to the mother.

Prolonged high maternal glucose results in overstimulation of the fetal pancreas, resulting in too much insulin production. This causes low blood sugar upon birth. This occurs because a consistent glucose source is taken away (the mother’s nutrition), which can usually be relieved with breastfeeding, formula feeding, or sometimes a glucose drip for the first few days of life.

As neonatal hypoglycemia symptoms can be vague and nonspecific, clinicians and nursing staff in the newborn nursery may try to establish that the infant can maintain target range blood glucose levels before being discharged home.

It’s possible that symptoms may not materialize until after the first 48 hours of life. Keeping an eye out for symptoms can help parents spot them in their newborn. A new parent may notice:

  • weak or high-pitched cry
  • tremors
  • sweating
  • feeding difficulties, poor suck
  • irritability
  • seizures

Neonatal hyperglycemia is high blood glucose at birth. Neonatal hyperglycemia is defined as either:

  • serum glucose higher than 150 mg/dL
  • whole blood glucose higher than 125 mg/dL at any gestational age at birth

Neonatal hyperglycemia is less common than neonatal hypoglycemia. It usually resolves within the first few days of life, but it can last up to 10 days.

The treatment of neonatal hyperglycemia includes reducing the amount of glucose given to your infant in their first few days after birth (which is normally given to infants to maintain high enough blood glucose levels), starting your infant on insulin therapy, or both.

According to the American Diabetes Association, neonatal diabetes is defined as a diagnosis within the first 6 months after birth. Unlike type 1 diabetes, this neonatal diabetes is often caused by a genetic defect and can be diagnosed as soon as the fifth day of life.

This comes before most typical diagnosis techniques are used and usually results in extremely high blood sugar and diabetic ketoacidosis (DKA). Doing a genetic test with only slightly elevated blood glucose levels can be safer to ensure prompt diagnosis and the start of treatment.

The first steps to diagnosing neonatal diabetes are:

Warnings signs of diabetes

Since most mothers and babies are discharged from the hospital before a neonatal diabetes diagnosis can be made, it’s crucial to keep your eyes peeled for symptoms.

Undiagnosed neonatal diabetes (just like type 1 diabetes in older children and adults) can lead to serious complications such as DKA, which can lead to neurological damage and even death.

Additional symptoms of neonatal diabetes include:

  • frequent urination/constant wet diapers
  • dehydration
  • weight loss
  • rapid breathing
  • sluggishness
  • constantly sleepy
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Blood glucose levels are typically lower for newborn babies, with infants regularly having blood glucose levels as low as 25 mg/dL at birth and rising a few days after birth to between 60 to 100 mg/dL.

Some babies are born with neonatal hypoglycemia, which is a glucose level of less than 30 mg/dL at birth and less than 45 mg/dL several days after birth. Babies may also be born with neonatal hyperglycemia, which is serum glucose higher than 150 mg/dL or whole blood glucose higher than 125 mg/dL at birth. It usually resolves after several days.

Fluctuating glucose levels may be a sign of neonatal diabetes, which is diagnosed in the first 6 months and is often the result of a genetic mutation. Prompt detection, diagnosis, and treatment of neonatal diabetes are key, as undiagnosed neonatal diabetes can lead to DKA, neurological damage, and even death.