How do you calculate the bolus insulin dose an individual needs?

How to Calculate Bolus Insulin Dose

The bolus insulin dose calculation requires two key components: the insulin-to-carbohydrate ratio (ICR) for meal coverage and the correction factor (insulin sensitivity factor) for addressing high blood glucose levels, with the total bolus dose being the sum of these two calculations. 1

Basic Formula for Bolus Insulin Calculation

• Total Bolus Insulin = Meal Bolus + Correction Bolus 2
• Meal Bolus = Carbohydrate grams ÷ Insulin-to-Carbohydrate Ratio 2
• Correction Bolus = (Current BG - Target BG) ÷ Correction Factor 2

Determining Insulin-to-Carbohydrate Ratio (ICR)

• ICR represents how many grams of carbohydrate are covered by 1 unit of insulin 1
• For breakfast: ICR = 300 ÷ Total Daily Dose (TDD) of insulin 3
• For lunch and dinner: ICR = 400 ÷ Total Daily Dose (TDD) of insulin 3
• Example: If TDD = 50 units, breakfast ICR = 300 ÷ 50 = 6 (1 unit covers 6g carbs) 3

Determining Correction Factor (Insulin Sensitivity Factor)

• Correction Factor = 1800 ÷ Total Daily Dose (TDD) of insulin 4
• This indicates how much 1 unit of insulin will decrease blood glucose 1
• Example: If TDD = 50 units, Correction Factor = 1800 ÷ 50 = 36 (1 unit lowers BG by 36 mg/dL) 4

Practical Example

For a patient with:

• Blood glucose of 250 mg/dL
• Target blood glucose of 125 mg/dL
• Carbohydrate intake of 60g
• ICR of 1:10
• Correction factor of 1:25

Calculate:

1. Meal bolus: 60g ÷ 10 = 6 units
2. Correction bolus: (250 - 125) ÷ 25 = 5 units
3. Total bolus: 6 + 5 = 11 units 2

Factors Affecting Insulin Calculations

• Time of day (morning insulin resistance due to dawn phenomenon) 1
• Exercise (can increase insulin sensitivity) 1
• Illness (can decrease insulin sensitivity) 1
• Menstrual cycles in women (can affect insulin requirements) 1
• Meal composition beyond carbohydrates (fat and protein content) 1

Avoiding Common Pitfalls

• Not accounting for "insulin on board" from previous boluses can lead to insulin stacking and hypoglycemia 1
• Using a fixed ICR throughout the day ignores diurnal variations in insulin sensitivity 1
• Failing to adjust ICR and correction factor with changes in weight, activity levels, or insulin requirements 1
• Overestimating or underestimating carbohydrate content in meals 1
• Not considering meal composition beyond carbohydrates (fat and protein delay absorption) 5

Technology Support for Bolus Calculations

• Bolus calculators in insulin pumps and smartphone apps can improve accuracy 6
• Studies show that bolus calculators help achieve target postprandial glucose with fewer correction boluses 6
• Advanced systems may use machine learning to optimize meal ratios over time 1

Periodic Reassessment

• ICR and correction factor should be reassessed regularly as insulin requirements change 1
• Adjustments needed with significant weight changes, activity level changes, or seasonal variations 4
• At least 1-2 weeks of blood glucose data should be reviewed when making adjustments 1