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What is hypoglycemia and low blood sugar?

Hypoglycemia is the state of having a blood glucose level that is too low to effectively fuel the body's cells.

Glucose, which comes from carbohydrates found in foods, is a main source of energy for all of the cells of the body and, especially, the brain. While the body is quite good at extracting glucose from the foods we eat, it relies on a hormone called insulin to actually get the glucose inside the cells of specific organs: the liver, fat, and muscle.

We can think of insulin as holding the “key” to a cell — without insulin, the glucose just remains in the blood, where it’s also known as “blood sugar.” During an episode of hypoglycemia, there’s not enough glucose in the blood. The normal range is approximately 70 to 150 mg/dl (milligrams of glucose per deciliter of blood).

Hypoglycemia is most common in newborns. In older children, it’s most often seen as a complication of insulin therapy for diabetes but can sometimes have other causes as well.

In the majority of cases, hypoglycemia is temporary, easily treated, and usually does not have serious consequences. There are several rare disorders in which hypoglycemia is recurrent and potentially life-threatening. However, with timely diagnosis and appropriate treatment, these can be effectively managed.

What are the symptoms of hypoglycemia?

While each child may experience symptoms of hypoglycemia differently, the most common include:

  • shakiness
  • dizziness
  • sweating
  • hunger
  • headache
  • irritability
  • pale skin color
  • sudden moodiness or behavior changes, such as crying for no apparent reason
  • clumsy or jerky movements
  • difficulty paying attention or confusion

What causes hypoglycemia?

The vast majority of episodes of hypoglycemia in children and adolescents occur when a child with diabetes takes too much insulin, eats too little, or exercises strenuously or for a prolonged period of time.

For young children who do not have diabetes, hypoglycemia may be caused by:

Single episodes:

  • stomach flu or another illness that may cause them to not eat enough
  • fasting for a prolonged period of time
  • prolonged strenuous exercise and lack of food

Recurrent episodes:

  • accelerated starvation, also known as “ketotic hypoglycemia,” a tendency for children without diabetes, or any other known cause of hypoglycemia, to experience repeated hypoglycemic episodes
  • medications your child may be taking
  • a congenital (present at birth) error in metabolism or unusual disorder such as hypopituitarism or hyperinsulinism

How we care for hypoglycemia

At Boston Children’s Hospital, we treat hypoglycemia in our General Endocrinology Program, a multi-disciplinary program dedicated to the treatment of a wide range of endocrinological disorders. Caring for more than 7,000 patients each year, our division is one of the largest pediatric endocrinology practices in the country. We provide state-of-the-art diagnosis, treatment, and clinical management for children with hypoglycemia and related disorders.

Hypoglycemia and Low Blood Sugar | Diagnosis & Treatments

How is hypoglycemia diagnosed?

If your child has diabetes, hypoglycemia is usually caused by insulin reaction, a common complication of diabetes. For children who have symptoms of hypoglycemia and don’t have diabetes, in addition to a complete medical history and physical exam, your child’s physician will look for evidence of what’s known as the Whipple Triad:

  • symptoms known or likely to be caused by hypoglycemia
  • low plasma glucose measured at the time of the symptoms
  • relief of symptoms when glucose is raised to normal

The doctor also may order laboratory tests to measure your child’s insulin production.

What are the treatment options for hypoglycemia?

Children with hypoglycemia have different symptoms, and these vary from one child to another. But no matter what your child’s symptoms, the overriding goal is the same — to bring the blood sugar back up to normal as rapidly as possible and return your child to good health.

Most often, your child’s blood sugar can be brought back up to normal by eating or drinking something that has sugar in it, such as fruit juice, regular soda, table sugar, maple syrup, candy, glucose tablets, glucose gel, or cake frosting. Consider encouraging your child to:

  • eat regular meals throughout the day
  • eat frequent snacks

For children with diabetes, the goal is to consistently maintain a blood sugar level that is in a healthy range. This involves testing blood sugar often, learning to recognize the earliest symptoms of low blood sugar, and treating the condition quickly, based on instructions given by your child's healthcare providers.

If your child has recurrent or severe hypoglycemia, the first thing is to determine the cause, because different causes have different treatments. While the cause is determined, some children will receive glucose intravenously (through an IV) in the hospital to make sure their blood-sugar level stays normal.

Some causes of hypoglycemia can be treated with changes in your child’s diet or medication. For some rare cases of severe hypoglycemia that don’t respond to medical treatment, the doctor may recommend surgery to remove most of the pancreas.

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