What is hypoglycemia?

Hypoglycemia: Definition and Clinical Classification

Hypoglycemia is defined as a blood glucose level below 70 mg/dL (3.9 mmol/L), with severity classified into three distinct levels based on glucose measurements and clinical manifestations. 1

Classification of Hypoglycemia

Hypoglycemia is categorized into three levels according to the most recent guidelines:

1. Level 1 Hypoglycemia:

   • Blood glucose <70 mg/dL (3.9 mmol/L) but ≥54 mg/dL (3.0 mmol/L)
   • Considered clinically important regardless of symptoms
   • Represents the threshold for neuroendocrine responses to falling glucose
   • Often associated with early warning symptoms (adrenergic)

2. Level 2 Hypoglycemia:

   • Blood glucose <54 mg/dL (3.0 mmol/L)
   • Threshold at which neuroglycopenic symptoms begin
   • Requires immediate action to resolve
   • Clinically significant and should be reported in clinical trials

3. Level 3 Hypoglycemia:

   • Severe event characterized by altered mental and/or physical functioning
   • Requires assistance from another person for recovery
   • May occur at any glucose level
   • Can progress to loss of consciousness, seizure, coma, or death

Clinical Manifestations

Hypoglycemia symptoms fall into two categories:

• Neurogenic (autonomic) symptoms:

  • Shakiness
  • Irritability
  • Hunger
  • Sweating
  • Tachycardia
  • Anxiety

• Neuroglycopenic symptoms (typically appear at Level 2):

  • Confusion
  • Weakness
  • Visual disturbances
  • Difficulty speaking
  • Headache
  • Dizziness
  • Cognitive impairment

Risk Factors and Clinical Significance

Hypoglycemia is the major limiting factor in glycemic management of diabetes 1. High-risk populations include:

• Patients on insulin therapy
• Those taking sulfonylureas or meglitinides
• Elderly patients (≥75 years)
• Patients with impaired hypoglycemia awareness
• Those with end-stage kidney disease
• Individuals with cognitive impairment or dementia
• Recent history of severe hypoglycemia

Management Principles

1. Immediate treatment for conscious patients with hypoglycemia:

   • 15-20g of glucose is preferred (any carbohydrate containing glucose may be used)
   • Recheck glucose after 15 minutes; repeat treatment if hypoglycemia persists
   • Once glucose is trending up, consume a meal or snack to prevent recurrence 1

2. For severe hypoglycemia (Level 3):

   • Requires assistance from another person
   • Treatment with glucagon (intramuscular/subcutaneous) or concentrated intravenous glucose
   • Glucagon should be prescribed for all individuals at risk for level 2 or 3 hypoglycemia 2

Prevention Strategies

• Continuous glucose monitoring (CGM) is beneficial and recommended for individuals at high risk 1
• Regular assessment of hypoglycemia awareness
• Medication adjustment to reduce risk
• Structured education for hypoglycemia prevention and treatment
• Reassessment of treatment plan after episodes of level 2 or 3 hypoglycemia

Special Considerations

• Hypoglycemia unawareness: Impaired ability to perceive warning symptoms of falling blood glucose, significantly increasing risk for severe hypoglycemia
• Cognitive function: Regular assessment is important as cognitive impairment increases hypoglycemia risk and hypoglycemia may worsen cognitive function 1
• Hospitalized patients: Same classification applies, with particular vigilance needed in critical care settings 3

Hypoglycemia represents a significant clinical concern with potential for serious morbidity and mortality, particularly in patients with diabetes on glucose-lowering medications. Early recognition and prompt treatment are essential to prevent progression to more severe forms.