At what blood glucose level should rapid acting insulin be held in a diabetic patient with a history of hypoglycemia?

Holding Rapid-Acting Insulin Based on Blood Glucose Levels

Rapid-acting insulin should be held when blood glucose falls below 70 mg/dL (3.9 mmol/L), and the insulin regimen must be reassessed and modified when blood glucose values are below 100 mg/dL (5.6 mmol/L) to prevent hypoglycemia, particularly in patients with a history of hypoglycemia. 1

Critical Thresholds for Insulin Management

Primary Action Threshold: <70 mg/dL

• Blood glucose <70 mg/dL (3.9 mmol/L) represents Level 1 hypoglycemia and is the hypoglycemia alert value where rapid-acting insulin must be withheld and treatment with 15-20 grams of fast-acting carbohydrates should be initiated immediately. 1, 2
• This 70 mg/dL threshold is the standard definition that correlates with the initial release of counterregulatory hormones and marks the point where intervention is required. 1

Reassessment Threshold: <100 mg/dL

• When blood glucose falls below 100 mg/dL (5.6 mmol/L), consideration should be given to reassessing the entire insulin regimen, not just holding a single dose, to prevent progression to true hypoglycemia. 1
• This is particularly critical in hospitalized patients where 84% of severe hypoglycemic episodes (<40 mg/dL) were preceded by earlier hypoglycemia (<70 mg/dL) during the same admission. 1

Special Considerations for High-Risk Patients

Patients with History of Hypoglycemia

• In patients with documented hypoglycemia unawareness or recurrent Level 2 hypoglycemia (<54 mg/dL), insulin should be held at higher thresholds and glycemic targets should be temporarily raised to strictly avoid hypoglycemia for several weeks. 1, 2
• The ADA specifically changed preprandial targets from 70-130 mg/dL to 80-130 mg/dL in 2015 to provide a safety margin and limit overtreatment in patients titrating insulin. 1

Hospitalized Patients

• For noncritically ill hospitalized patients, modification of the insulin regimen is required when blood glucose values fall below 70 mg/dL (3.9 mmol/L), unless the event is easily explained by other factors such as a missed meal. 1
• In the hospital setting, rapid-acting insulin should be administered every 4 hours as correctional insulin, with close monitoring to detect patterns requiring regimen adjustment. 1

Clinical Algorithm for Decision-Making

When blood glucose is checked before a meal:

1. ≥130 mg/dL: Administer scheduled rapid-acting insulin as prescribed 1
2. 100-129 mg/dL: Consider reducing the rapid-acting insulin dose by 25-50% depending on patient's hypoglycemia history 1
3. 70-99 mg/dL: Hold rapid-acting insulin; reassess regimen; patient should eat meal without insulin coverage 1
4. <70 mg/dL: Hold all insulin; treat hypoglycemia with 15-20g fast-acting carbohydrates; recheck in 15 minutes 1, 2

Important Pitfalls to Avoid

Common Errors in Practice

• Do not rely solely on sliding scale (correction-only) insulin without basal insulin, as this reactive approach is strongly discouraged and associated with poor glycemic control. 1
• Do not continue the same insulin doses after a hypoglycemic episode—75% of hospitalized patients had no dose adjustment made before the next insulin administration despite documented hypoglycemia, leading to recurrent events. 1

Timing Considerations

• Rapid-acting insulin analogs should be given 0-15 minutes before meals, so the decision to hold must be made at that time based on current blood glucose. 3
• For patients with poor or unpredictable oral intake, a basal-plus correction insulin approach is preferred over scheduled rapid-acting insulin to minimize hypoglycemia risk. 1

Fasting or NPO Patients

• Rapid-acting insulin should generally be held entirely in patients who are NPO or fasting, with blood glucose monitored every 2-4 hours and only short- or rapid-acting insulin given as needed for correction. 1
• Basal insulin should be continued but may need dose reduction of 25% to prevent hypoglycemia in fasting states. 1

Level 2 Hypoglycemia Threshold

• Blood glucose <54 mg/dL (3.0 mmol/L) represents Level 2 hypoglycemia, the threshold where neuroglycopenic symptoms begin and requires immediate action—all insulin should be held and aggressive treatment initiated. 1, 2
• This level of hypoglycemia should trigger immediate reevaluation of the entire diabetes treatment plan and consideration for glucagon prescription. 2