What is the range considered low blood glucose in a hospital setting for critically ill patients according to American Diabetes Association (ADA) guidelines?

Low Blood Glucose Range in Critically Ill Patients According to ADA 2025 Guidelines

According to the American Diabetes Association 2025 guidelines, low blood glucose (hypoglycemia) in hospitalized critically ill patients is defined as Level 1 hypoglycemia at <70 mg/dL (3.9 mmol/L) but ≥54 mg/dL (3.0 mmol/L), Level 2 (clinically significant) hypoglycemia at <54 mg/dL (3.0 mmol/L), and Level 3 (severe) hypoglycemia as any level associated with altered mental or physical functioning requiring assistance. 1

Hypoglycemia Classification System

The ADA uses a three-tiered classification system for hypoglycemia in hospitalized patients:

Level 1 Hypoglycemia (Alert Value)

• Blood glucose <70 mg/dL (3.9 mmol/L) but ≥54 mg/dL (3.0 mmol/L) 1
• This threshold of 70 mg/dL represents the point at which neuroendocrine counterregulatory responses begin in people without diabetes 1
• This is considered clinically important regardless of symptom severity, particularly because many patients with diabetes have impaired counterregulatory responses or hypoglycemia unawareness 1
• The hypoglycemia alert value in hospitalized patients is specifically defined as blood glucose ≤70 mg/dL (3.9 mmol/L) 1

Level 2 Hypoglycemia (Clinically Significant)

• Blood glucose <54 mg/dL (3.0 mmol/L) 1
• This is the threshold at which neuroglycopenic symptoms typically begin to occur 1
• Requires immediate action to resolve the hypoglycemic event 1
• This level is considered clinically significant hypoglycemia in the hospital setting 1

Level 3 Hypoglycemia (Severe)

• Characterized by altered mental and/or physical functioning requiring assistance from another person for recovery, regardless of the actual blood glucose level 1
• This definition emphasizes functional impairment rather than a specific glucose threshold 1

Clinical Action Thresholds

When to Reassess Insulin Regimen

• Blood glucose <100 mg/dL should trigger reassessment of the insulin regimen 1, 2, 3
• This threshold is important because fasting glucose <100 mg/dL predicts hypoglycemia within the next 24 hours 2, 3

When to Modify Treatment

• Blood glucose <70 mg/dL (3.9 mmol/L) requires modification of the insulin regimen 1
• Modification is mandatory unless the hypoglycemic event is easily explained by other factors such as a missed meal 1

Research Context on Hypoglycemia Definitions

Earlier consensus recommendations from critical care societies defined hypoglycemia thresholds differently for research reporting purposes:

• Moderate hypoglycemia: 2.3 to 3.9 mmol/L (41 to 70 mg/dL) 1
• Severe hypoglycemia: ≤2.2 mmol/L (≤40 mg/dL) 1

However, the 2015 ADA guidelines noted that severe hypoglycemia in hospitalized patients had been defined by many as <40 mg/dL (2.2 mmol/L), though this is lower than the <50 mg/dL (2.8 mmol/L) level at which cognitive impairment begins 1

Important Clinical Considerations

Hypoglycemia and Mortality Risk

• Even mild to moderate hypoglycemia (40-69 mg/dL) is associated with adverse outcomes in critically ill patients 1
• Early recognition and treatment of mild to moderate hypoglycemia can prevent deterioration to more severe episodes with potential adverse sequelae 1
• Hypoglycemia is independently associated with increased risk of death, cardiovascular death, and death due to infectious disease in critically ill patients 4
• The more severe the hypoglycemia, the greater the risk of death 4

Documentation Requirements

• Episodes of hypoglycemia in the hospital should be documented in the medical record and tracked 1
• For severe hypoglycemia, documentation should include duration, associated symptoms, amount of glucose administered, and the next blood glucose concentration 1
• Hypoglycemia should be reported separately as iatrogenic (related to insulin treatment) versus spontaneous (unrelated to insulin treatment) 1