Hypoglycaemia

Most common side effect of insulin therapy

Definition

Hypoglycemia is a condition where blood glucose levels fall below normal physiologic range, typically:
  • <70 mg/dL (3.9 mmol/L) — alert threshold
  • <54 mg/dL (3.0 mmol/L) — clinically significant
  • <40 mg/dL — severe neuroglycopenic risk
Whipple’s Triad confirms true hypoglycemia:
  1. Symptoms of hypoglycemia
  1. Low plasma glucose
  1. Relief of symptoms after glucose correction

Aetiology

Diabetic Patients

Most common
  • Excess insulin or sulfonylureas
  • Skipped meals after insulin dose
  • Strenuous exercise
  • Alcohol intake
  • Renal insufficiency (reduces insulin clearance)

Non-diabetic Patients

  • Sepsis/critical illness
  • Liver failure (↓ gluconeogenesis)
  • Hormonal deficiencies (adrenal insufficiency, hypopituitarism)
  • Insulinoma (rare tumor)
  • Reactive/postprandial hypoglycemia
  • Alcohol-induced (inhibits gluconeogenesis)
  • Malnutrition

Clinical Manifestation

Adrenergic (Autonomic)

Due to catecholamine release:
  • Tremor
  • Palpitations
  • Anxiety
  • Sweating
  • Hunger
  • Paresthesia

Neuroglycopenic

Due to brain glucose deprivation:
  • Headache
  • Confusion
  • Blurred vision
  • Slurred speech
  • Seizures
  • Loss of consciousness
  • Coma (severe/prolonged)

Management

Immediate Treatment

Mild Hypoglycemia — If patient is compos mentis:
  • >70 mg/dL → patient can be asked to eat
  • <70 mg/dL → 15–20 g oral glucose (e.g., 3–4 glucose tablets, juice, candy)
  • Recheck glucose after 15 min → repeat up to 3x if still low
  • If blood glucose still low → IVFD Dextrose 10% 150-200 mL in 15 minutes
Severe Hypoglycemia — If unconscious or unable to swallow:
  • IV dextrose 10% 150-200 mL in 15 minutes
  • IV dextrose 20% 75-100 mL in 15 minutes
  • IV dextrose 40% 25-50 mL in 15 minutes
  • Recheck glucose after 15 min, if
    • <70 mg/dL, repeat bolus
    • >70 mg/dL, IV dextrose 10% 100 mL/hr until patient can eat