Hypoglycemia Cutoff in Adults
The cutoff for hypoglycemia in adults is a blood glucose level <70 mg/dL (<3.9 mmol/L), which represents the threshold where counterregulatory hormones are activated and clinically important hypoglycemia begins, regardless of whether symptoms are present. 1
Three-Level Classification System
The American Diabetes Association uses a standardized three-level classification that guides clinical management 1:
Level 1 Hypoglycemia (Alert Value)
- Glucose <70 mg/dL (<3.9 mmol/L) AND ≥54 mg/dL (≥3.0 mmol/L) 1
- This 70 mg/dL threshold represents where neuroendocrine responses to falling glucose begin in people without diabetes 1
- Clinically important even without severe symptoms because many patients with diabetes have impaired counterregulatory responses and reduced hypoglycemia awareness 1
- Treatment should be initiated at this level with 15-20 grams of fast-acting carbohydrates 1
Level 2 Hypoglycemia (Clinically Significant)
- Glucose <54 mg/dL (<3.0 mmol/L) 1
- This is the threshold where neuroglycopenic symptoms (confusion, altered mental status) typically begin 1
- Requires immediate action to resolve the hypoglycemic event 1
- Associated with cognitive impairment and increased risk of severe complications 1
Level 3 Hypoglycemia (Severe)
- Altered mental and/or physical status requiring assistance from another person for treatment, irrespective of the actual glucose level 1
- Can progress to loss of consciousness, seizure, coma, or death 1
- Requires glucagon administration or assistance with carbohydrate intake 1
Clinical Context and Symptoms
The 70 mg/dL cutoff is critical because 1:
- Symptoms include shakiness, irritability, confusion, tachycardia, sweating, and hunger 1
- Many patients with diabetes have impaired awareness and may not recognize symptoms until glucose drops much lower 1
- Patients with chronically poor glycemic control may experience symptoms at higher glucose levels than 70 mg/dL 2
Important Clinical Pitfalls
Do not wait for symptoms to treat hypoglycemia - the 70 mg/dL threshold should trigger treatment even in asymptomatic patients because counterregulatory responses are already compromised in diabetes 1. Recurrent hypoglycemia below 70 mg/dL creates a vicious cycle by further impairing the body's ability to recognize and respond to low glucose 3.
For patients on insulin, sulfonylureas, or meglitinides, any glucose reading <70 mg/dL warrants immediate carbohydrate intake and reassessment of the treatment regimen to prevent recurrence 1.