What Causes Low Blood Sugar in Young People
Low blood sugar (hypoglycemia) in young people is most commonly caused by diabetes treatment with insulin or sulfonylureas, but in non-diabetic youth, the causes vary by age and include hyperinsulinism, hormonal deficiencies, metabolic disorders, and ketotic hypoglycemia.
In Diabetic Youth
For children and adolescents with diabetes, hypoglycemia is the most frequent acute complication 1, 2. The primary causes are:
- Excessive insulin relative to needs (too much insulin, wrong timing, or incorrect dose)
- Insufficient food intake (skipped meals, delayed meals, or inadequate carbohydrate consumption)
- Increased physical activity without appropriate insulin or food adjustments
- Deviations from treatment routine 3
Nocturnal hypoglycemia is particularly common, occurring in 14-47% of diabetic children, often due to impaired counterregulatory responses during sleep and may be asymptomatic 4.
Critical Risk Factors in Diabetic Youth
Young children under 6 years face unique dangers because they often cannot recognize, articulate, or manage hypoglycemic symptoms—a condition called "hypoglycemia unawareness" 5. This developmental limitation makes them particularly vulnerable to severe episodes.
Repeated hypoglycemic episodes or long diabetes duration can cause defective glucose counterregulation, where the body fails to mount appropriate adrenergic responses, further increasing risk 4.
In Non-Diabetic Youth
The causes differ substantially by age group:
Neonates and Infants
In newborns and young infants, hypoglycemia typically results from 6, 7:
- Hyperinsulinism (transient neonatal, sustained, or drug-induced)
- Hormonal deficiencies (hypopituitarism, growth hormone deficiency, cortisol deficiency)
- Inborn errors of metabolism affecting carbohydrate, protein, or fat metabolism
- Hereditary hepatic enzyme deficiencies
- Substrate availability problems
Key clinical point: Neonatal hypoglycemia presents differently than in older children—with irritability, feeding difficulties, lethargy, cyanosis, tachypnea, and hypothermia rather than typical adrenergic symptoms 6.
Children Beyond Infancy
Ketotic hypoglycemia is the most common cause of hypoglycemia in non-diabetic children outside the neonatal period 7. This condition appears related to abnormalities in substrate availability during fasting.
Other causes include:
- Persistent hyperinsulinism
- Endocrine disorders (growth hormone deficiency, cortisol deficiency)
- Metabolic disorders (glycogen storage diseases, fatty acid oxidation defects)
- Critical illness or acquired conditions
- Ingestion of certain substances (alcohol, medications)
Diagnostic Approach
At the time of a spontaneous hypoglycemic episode, immediately obtain:
- Blood glucose level
- Insulin level
- Cortisol level
- Growth hormone level
- Urine for ketone bodies 7
These critical samples must be collected during the hypoglycemic event, as they provide essential diagnostic information that cannot be obtained later.
Clinical Presentation by Age
Symptoms are nonspecific, particularly in infants and young children 8:
- Infants/toddlers: Irritability, feeding difficulties, lethargy, inattention, falling asleep at inappropriate times, unexplained behavior, temper tantrums 2
- Older children/adolescents: Tremors, sweating, pallor, palpitations, headache, confusion, behavior changes, drowsiness 4
- Severe cases (any age): Altered consciousness, seizures, coma 4
Critical Pitfalls to Avoid
Never delay treatment while waiting for confirmatory laboratory results—treat based on point-of-care glucose if hypoglycemia is suspected 2
Do not assume all hypoglycemia in young people is diabetes-related—persistent or recurrent hypoglycemia in non-diabetic children requires comprehensive metabolic and endocrine evaluation 8, 9
Young children require lower glucose thresholds for treatment initiation and higher target ranges due to their vulnerability to brain injury 4
Recognize that hypoglycemia can cause permanent neurological damage, particularly with prolonged or recurrent severe episodes in younger children, making prevention paramount 3
In diabetic youth, assess for hypoglycemia unawareness at every visit, as this dramatically increases risk and requires modification of treatment targets 4