Blood Glucose Threshold for Insulin Administration

Rationale for the Threshold

The American Diabetes Association defines hypoglycemia as any blood glucose level <70 mg/dL (3.9 mmol/L), which represents the initial threshold for counterregulatory hormone release 1, 2
Level 1 hypoglycemia is classified as glucose <70 mg/dL (3.9 mmol/L) and ≥54 mg/dL (3.0 mmol/L), according to the American Diabetes Association 1, 3

Administering insulin when blood glucose is below 70 mg/dL (3.9 mmol/L) significantly increases the risk of developing more severe hypoglycemia, as stated by the American Diabetes Association 1
The American Diabetes Association recommends that level 2 hypoglycemia (<54 mg/dL or 3.0 mmol/L) is the threshold at which neuroglycopenic symptoms begin to occur 1
Severe hypoglycemia can lead to significant morbidity including cognitive impairment, seizures, coma, and in rare cases, mortality, according to the American Diabetes Association 4, 5

Before administering insulin, blood glucose should be checked to ensure it is ≥70 mg/dL (3.9 mmol/L), as recommended by the American Diabetes Association 1, 4
If blood glucose is <70 mg/dL (3.9 mmol/L), hypoglycemia should be treated first before insulin administration, according to the American Diabetes Association 1

For hospitalized patients, insulin regimens should be reassessed if blood glucose falls below 100 mg/dL (5.6 mmol/L) to prevent hypoglycemia, as stated by the American Diabetes Association 4, 5
Patients with a history of hypoglycemia unawareness may require higher glucose thresholds before insulin administration, according to the American Diabetes Association 1, 3

Never administer insulin when blood glucose is already in the hypoglycemic range (<70 mg/dL or 3.9 mmol/L), as recommended by the American Diabetes Association 1, 4
Avoid relying solely on symptoms to determine if a patient is hypoglycemic; always confirm with blood glucose measurement, according to the American Diabetes Association 1, 2
The risk of hypoglycemia is higher in patients with renal impairment, liver disease, and the elderly, as stated by the American Diabetes Association 1, 2