History
The patient's medication and drug history should be reviewed carefully for potential causes of hypoglycemia. Inquire if the patient is taking any new medications. A history of insulin usage or ingestion of an oral hypoglycemic agent may be known, and possible toxic ingestion should be considered. Injecting a shot of insulin and skipping a meal or overdosing insulin is the most common cause in patients with diabetes. It is important to determine how the patient is taking oral insulin secretagogues, particularly sulfonylureas. Often, those with nocturnal hypoglycemia are taking the drug late at night after supper. A careful history will uncover this.
The medical history may include diabetes mellitus, renal insufficiency/failure, alcoholism, hepatic cirrhosis/failure, other endocrine diseases, or recent surgery. However, obtaining an accurate medical history may be difficult if the patient's mental status is altered. Central nervous system (CNS) symptoms include headache, confusion, and personality changes.
The social history may include ethanol intake and nutritional deficiency.
Review systems for weight reduction, fatigue, somnolence, nausea and vomiting, and headache. Look for other symptoms suggesting infection.
Neurogenic or neuroglycopenic symptoms
Symptoms of hypoglycemia may be categorized as neurogenic (adrenergic) or neuroglycopenic. Sympathoadrenal activation symptoms include sweating, shakiness, tachycardia, anxiety, and a sensation of hunger. Neuroglycopenic symptoms include weakness, tiredness, or dizziness; inappropriate behavior (sometimes mistaken for inebriation), difficulty with concentration; confusion; blurred vision; and, in extreme cases, coma and death.
The timing of onset of symptoms relative to the time of meal ingestion is crucial in the evaluation of a patient with hypoglycemia. Fasting hypoglycemia typically occurs in the morning before eating or during the day, particularly in the afternoon if meals are missed or delayed.
Postprandial hypoglycemia typically occurs 2-4 hours after eating food, especially when meals contain high levels of simple carbohydrates. Postprandial symptoms are typically due to reactive causes, but some patients with insulinoma also may present with postprandial symptoms. About 4-6 hours after food ingestion, plasma glucose concentrations are 80-90 mg/dL, and rates of glucose utilization and production are approximately 2 mg/kg/min. Glucose production is primarily (70-80%) from hepatic glycogenolysis, with a lesser contribution (20-25%) from hepatic gluconeogenesis.
A study by Feil et al found a high risk of hypoglycemia among patients with dementia and cognitive impairment. [20]
Reactive hypoglycemic symptoms
Reactive hypoglycemia seldom causes glucose levels to drop low enough to induce severe neuroglycopenic symptoms; therefore, a history of true loss of consciousness is highly suggestive of an etiology other than reactive hypoglycemia.
Reactive hypoglycemia has been suggested to be more common in overweight and obese people who are insulin-resistant, and it may be a frequent precursor to type 2 diabetes. Therefore, patients who have a family history of type 2 diabetes or insulin-resistance syndrome (ie, hypertension, hyperlipidemia, obesity) may be at higher risk for developing hypoglycemia.
Gestational hypoglycemia
In a study of maternal hypoglycemia, Pugh et al found that hypoglycemia occurred more frequently in women younger than 25 years and those who had a preexisting medical condition. [2] Hypoglycemia was less frequent in women whose prepregnancy body mass index (BMI) was ≥ 30 kg/m2. The investigators also found that patients with hypoglycemia were at greater risk of preeclampsia/eclampsia.
Physical Examination
Physical findings are nonspecific in hypoglycemia and generally are related to the central and autonomic nervous systems. Assess vital signs for hypothermia, tachypnea, tachycardia, hypertension, and bradycardia (neonates).
The head, eyes, ears, nose, and throat (HEENT) examination may indicate blurred vision, pupils normal to fixed and dilated, icterus (usually cholestatic due to hepatic disease), and parotid pain (due to endocrine causes).
Cardiovascular disturbances may include tachycardia (bradycardia in neonates), hypertension or hypotension, and dysrhythmias. Neurologic conditions include coma, confusion, fatigue, loss of coordination, combative or agitated disposition, stroke syndrome, tremors, convulsions, and diplopia.
Respiratory disturbances may include dyspnea, tachypnea, and acute pulmonary edema. Gastrointestinal disturbances may include nausea and vomiting, dyspepsia, and abdominal cramping.
The patient's skin may be diaphoretic and warm or show signs of dehydration with decrease in turgor.
Symptoms of hypoglycemia are fewer in elderly persons and they frequently appear at a lower threshold of plasma glucose than in younger persons.
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Diagnostic algorithm. A systematic approach is often required to establish the true cause of hypoglycemia, using an algorithmic approach.
