In infants and toddlers, signs and symptoms of hypoglycemia can often be vague and subtle. Given the subtle and nonspecific findings of the signs and symptoms, the detection of hypoglycemia is dependent on a high index of suspicion.

Symptoms of hypoglycemia can be characterized into two physiologic categories: activation of the autonomic nervous system characterized by an adrenergic symptoms and neuroglycopenic (cerebral glycopenia) symptoms. When serum glucose levels are <40 mg/dL, it may produce hunger and trigger an adrenergic response. Common adrenergic symptoms include jitteriness, anxiety, sweating, tachycardia, pallor, weakness, nausea, and emesis. Neuroglycopenic symptoms include headache, dizziness, mental dullness, fatigue, difficulty concentrating, confusion, personality changes, visual changes, seizures, and coma. Neonatal symptoms include those seen in children, such as tremors, jitteriness, and tachycardia, but may also present with nonspecific signs, such as tachypnea, apnea, cyanosis, hypotonia, feeding difficulty, abnormal cry, seizures, and coma.

The differential diagnosis and management of hypoglycemia is extensive and requires an understanding of the pathogenesis. Hypoglycemia may result from disorders of gluconeogenesis, glycogen metabolism, lipid oxidation, or amino acid metabolism.

The serum glucose should be measured to confirm hypoglycemia. Determining whether a patient is ketotic is an important decision for generating a differential diagnosis. There are two major categories: nonketotic hypoglycemia and ketotic hypoglycemia.

Those disorders that result in nonketotic hypoglycemia involve the inability to produce glucose and appropriate forms of energy despite appropriate glycogen storage. A prominent effect of insulin and counterregulatory hormones is to suppress lipolysis and ketogenesis. Therefore, those etiologies that involve high levels of insulin or lack of counterregulatory hormones do not generate high levels of ketones. These etiologies include hyperinsulinism for islet cell adenomas or overproduction, infants of diabetic mothers,
congenital panhypopituitarism, congenital adrenal hyperplasia, fatty oxidation defects, and Beckwith-Wiedemann syndrome.