When should an insulin bolus be administered?

When to Administer Insulin Bolus

Insulin bolus should be administered 15-20 minutes before meals for optimal postprandial glucose control, with adjustments based on meal content and current blood glucose levels. 1

Timing of Bolus Administration

Pre-Meal Bolus (Recommended)

• Administer rapid-acting insulin (insulin aspart, lispro, glulisine) 15-20 minutes before meals 1
• Benefits:
  • 30% reduction in postprandial glucose excursions compared to immediate pre-meal dosing 1
  • Lower peak blood glucose levels 2
  • Reduced glycemic area under the curve (AUC) 2
  • Less hypoglycemia risk compared to post-meal dosing 1

Immediate Pre-Meal Bolus

• Administer immediately before starting the meal
• Less effective than 15-20 minutes pre-meal bolus but better than post-meal dosing 2
• May be appropriate when:
  • Blood glucose is already low or borderline
  • Meal content is uncertain
  • Patient has gastroparesis

Post-Meal Bolus (Not Recommended for Routine Use)

• Associated with:
  • Higher postprandial glucose excursions 2
  • Greater risk of hypoglycemia 1
  • Only appropriate in specific situations (e.g., unpredictable food intake, nausea)

Bolus Types and Special Considerations

Standard Bolus

• Delivers total dose at once
• Best for meals with moderate glycemic index and balanced macronutrients 3

Extended/Dual-Wave Bolus

• For meals high in fat or protein, or with low glycemic index 4
• Portion of insulin delivered immediately, remainder over extended period
• Particularly useful for:
  • High-fat meals
  • Gastroparesis
  • Extended eating occasions (parties, buffets)

Meal-Related Factors

Carbohydrate Counting

• Calculate bolus using formula: (carbohydrates ÷ carbohydrate ratio) + correction factor 5
• Typical starting carbohydrate ratio: 1 unit per 10-15g carbohydrates 5

Correction Factor

• Calculate using formula: (current glucose - target glucose) ÷ insulin sensitivity factor 5
• Insulin sensitivity factor can be estimated by dividing 1800 by total daily insulin dose 5

Common Pitfalls and How to Avoid Them

Late Bolusing

• Late boluses (defined as glucose rise ≥50 mg/dL before bolus) occur approximately twice per week per patient 6
• Associated with worse glycemic control and higher HbA1c 6
• Solution: Set reminders for pre-meal bolusing

Missed Boluses

• Missed boluses (glucose rise ≥50 mg/dL without bolus within 2 hours) occur approximately 17 times per week per patient 6
• Strongly associated with poor glycemic control 6
• Solution: Use technology (smart pens, apps) to track and remind about bolus timing

Stacking Insulin

• Administering additional bolus before previous dose has completed its action
• Can lead to severe hypoglycemia
• Solution: Consider insulin on board when calculating correction doses 4

Special Situations

Perioperative Management

• For patients on insulin pump: maintain basal infusion during surgery 4
• If patient cannot manage pump postoperatively, initiate basal-bolus scheme by subcutaneous injection 4
• When transitioning from IV to subcutaneous insulin:
  • Administer basal insulin immediately after stopping IV infusion 4
  • Give first bolus of rapid-acting insulin with first meal 4

During Fasting

• Prandial insulin should be reduced or omitted during fasting periods 4
• For mixed insulin regimens, reduce dose by 25-35% for meals followed by fasting 4

By following these evidence-based guidelines for insulin bolus timing and administration, patients can achieve better postprandial glucose control, reduce glycemic variability, and potentially improve long-term outcomes.