What is low blood sugar or hypoglycemia?

Low blood sugar – also called hypoglycemia – refers to a blood concentration of glucose (sugar) that is too low to fuel the brain and the body. 

Glucose is the main source of fuel for the body, particularly the brain. The normal range of blood glucose, depending on the timing and nutritional content of the last meal consumed, is approximately 70 to 140 mg/dl (milligrams of glucose per deciliter of blood). 

Hypoglycemia can be the main sign of many different medical conditions. It can also be a complication of the treatment for diabetes, particularly in patients treated with insulin. This page focuses on low blood sugar as a sign of an underlying medical condition, as opposed to hypoglycemia as a complication seen in infants and children with diabetes.

Hypoglycemia in infants

Hypoglycemia in infants (less than 12 months old) can be hard to detect because symptoms often can be mild or hard to notice. Some babies may not show any signs at all. But hypoglycemia can cause serious complications for newborns and infants, so early detection and treatment is essential. With prompt care, most babies recover well. 

For newborns, blood sugar levels are lower during the first 2-3 days of life. Doctors may use slightly different cutoffs for low blood sugar during this transitional period in newborns. 

Infants are more likely to develop more serious hypoglycemia if they are: 

• Born to a parent with diabetes 
• Small for gestational age (SGA) or large for gestational age (LGA) 
• Born preterm 
• Born under significant stress 
• Exposed to certain maternal medications such as terbutaline or beta‑blockers  
• Affected by genetic syndromes (for example, Beckwith‑Wiedemann) or metabolic/hormonal disorders 
• Have a sibling or parent with a genetic disorder that causes hypoglycemia 

What are the signs and symptoms of hypoglycemia in infants and children?

Each child may experience hypoglycemia signs and symptoms differently. But the most common signs and symptoms for children 12 months and older may include: 

• Fast-beating, fluttering or pounding heart (palpitations) 
• 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 
• Loss of consciousness 
• Seizure

Hypoglycemia signs and symptoms in newborns and infants 

For newborns and infants up to 12 months, signs and symptoms of hypoglycemia may be subtle or even absent. Signs and symptoms to look out for in this age group are: 

• Poor feeding or trouble latching 
• Low energy or unusual sleepiness 
• Jitteriness or shakiness 
• Weak or high-pitched cry 
• Low body temperature (cold or clammy skin) 
• Breathing problems (fast or pauses in breathing) 
• Seizures (in severe cases) 

When should I seek care for my infant?

Call your doctor or seek emergency care if your baby: 

• Is hard to wake or very sleepy 
• Is not feeding well 
• Has shaking, jerking movements or seizures 
• Has trouble breathing 

If you are concerned about your baby’s blood sugar, trust your instincts and seek care right away. 

What causes hypoglycemia in infants and children?

Hypoglycemia happens when there is not enough glucose (sugar) in the blood to meet the body’s needs. The body gets glucose from what we eat and drink, but it can also store and make glucose to use between meals or overnight, while we are sleeping. If these processes do not work as they should, blood sugar can drop too low.  

Hormones help to control your glucose levels. Insulin lowers glucose levels, while other hormones like growth hormone and cortisol help to raise them. If the body makes too much insulin, or not enough growth hormone or cortisol, hypoglycemia can occur. The liver also plays an important role by storing and releasing glucose when the body needs it. Because of this, some liver conditions that affect these processes can also cause hypoglycemia.

In newborns and infants, hypoglycemia often happens for different reasons than in older children. Common causes in infants less than 12 months old include: 

• Too much insulin (hyperinsulinism). For this age group, hyperinsulinism (HI) is the most common medical condition that causes persistent low blood sugar. In hyperinsulinism, the beta cells of the pancreas release too much insulin, which results in hypoglycemia. HI has multiple causes, including maternal diabetes, fetal stress prior to or during delivery, or genetic defects. 
• Not getting enough nutrition (feeding challenges) 
• Problems with hormones (such as cortisol or growth hormone) 
• Metabolic or genetic conditions that affect how the body makes or stores glucose 
• Surgeries that alter the gastrointestinal tract (the path food takes from mouth to elimination) such as surgery to prevent reflux, known as fundoplication. In these cases, low blood sugar develops after surgery. What distinguishes this type of hypoglycemia is that low blood sugar occurs shortly after a meal rather than during fasting. This form of hypoglycemia is known as postprandial hypoglycemia, or late dumping syndrome. 

Other causes of hypoglycemia in children 12 months and older include: 

• Insulinomas (pancreatic tumors that release insulin) 
• Problems with hormones (such as cortisol or growth hormone) 
• Genetic defects in the liver that affect its ability to release glucose.  
• Accidental or intentional ingestions, such as taking certain medications or consuming alcohol. 

Why is hypoglycemia a concern for infants and children?

The brain depends on blood glucose as its main source of fuel. Too little glucose can impair the brain's ability to function. Severe or prolonged hypoglycemia may result in seizures and serious brain injury, or even death. 

How is hypoglycemia diagnosed?

In addition to a complete medical history and physical examination, certain blood tests are performed to diagnose hypoglycemia. 

For those who have symptoms of hypoglycemia and do not have diabetes:

• The underlying disorder is typically diagnosed by measuring blood glucose and other metabolic fuels such as lactate and ketones, and hormone levels while the child is experiencing the symptoms. 
• In newborns, blood sugar is often checked shortly after birth, especially if the baby is at higher risk. This is usually done with a small heel stick blood test. If low blood sugar continues, doctors may perform additional testing to find the cause. 
• Diagnosing the cause of the hypoglycemia in infants may require frequent glucose checks and, in some cases, supervised fasting studies. 
• Some children may need to stay in the hospital for a supervised fasting study to safely monitor and diagnose the condition. During a supervised fasting study your child will fast for a period of up to 48 hours (depending on their age), as clinical staff closely monitor their blood glucose and ketone levels through frequent blood draws. The test is ended when blood glucose drops too low, or if hypoglycemia symptoms occur. The idea is to understand how the body reacts in these situations, and pinpoint the cause of the hypoglycemia.

What is the treatment for hypoglycemia?

For children with hypoglycemia conditions, the goal of treatment is to maintain a safe blood glucose level. This involves testing blood glucose often, learning to recognize oncoming symptoms and treating the condition quickly, based on instructions given by your child's doctor. 

Treatment for hypoglycemia depends on:

• The specific condition that causes the hypoglycemia 
• Your child's age, overall health and medical history 
• Extent of the disorder 
• Your child's tolerance for specific medications, procedures or therapies 
• Expectations for the course of the disorder 
• Your opinion or preference 

For children, the immediate treatment for hypoglycemia is to give your child sugar quickly, such as orange juice, milk, cake icing, glucose gel or glucose tablets. If symptoms are more severe, your child may get intravenous fluids. 

Once they're born, some infants may need to stay in the hospital for monitoring until their blood sugar is stable. Most infants with hypoglycemia recover fully with prompt treatment. Some conditions may require ongoing care and follow-up.