How do you calculate a patient's correction insulin dose?

Calculating a Patient's Correction Insulin Dose

The correction insulin dose should be calculated using the patient's individualized insulin sensitivity factor (ISF), which equals 1800 divided by the patient's total daily insulin dose for regular insulin, or 1700 for rapid-acting analogs. 1

Understanding Correction Insulin

Correction insulin (also called supplemental insulin) is used to lower blood glucose levels that are above the target range. This differs from basal insulin (which provides background insulin) and mealtime bolus insulin (which covers carbohydrate intake).

Step-by-Step Calculation Method

1. Determine the insulin sensitivity factor (ISF):

   • For rapid-acting insulin: ISF = 1700 ÷ Total Daily Insulin Dose
   • For regular insulin: ISF = 1800 ÷ Total Daily Insulin Dose

2. Calculate the correction dose:

   Correction dose = (Current glucose - Target glucose) ÷ ISF

3. Account for insulin on board (IOB):

   • Subtract any active insulin from previous doses to prevent insulin stacking
   • Most insulin pumps automatically track IOB

Example Calculation

For a patient with a total daily insulin dose of 50 units using rapid-acting insulin:

• ISF = 1700 ÷ 50 = 34 mg/dL per unit
• If current glucose is 250 mg/dL and target is 120 mg/dL:
• Correction dose = (250 - 120) ÷ 34 = 3.8 units (round to 4 units)

Important Considerations

• Time of day matters: Insulin sensitivity often varies throughout the day, with many patients requiring more insulin per unit of carbohydrate in the mornings due to higher counter-regulatory hormone levels 1

• Adjust for special circumstances: Temporarily modify correction factors during illness, stress, or exercise

• Prevent hypoglycemia: If blood glucose is falling rapidly, consider reducing the calculated correction dose

• Monitor for insulin stacking: Avoid giving multiple correction doses too close together, as this can lead to hypoglycemia

Insulin Pump Settings

For patients on insulin pumps, the ISF is programmed directly into the device:

• The pump calculates correction doses automatically
• The ISF represents how much blood glucose will decrease with 1 unit of insulin
• Example: With an ISF of 1:3,1 unit of insulin would decrease blood glucose by 3 mmol/L 1

Common Pitfalls to Avoid

• Using a fixed correction dose for all patients rather than individualizing based on insulin sensitivity
• Ignoring insulin on board from previous doses, which can lead to dangerous hypoglycemia
• Failing to adjust correction factors when total daily insulin needs change
• Not accounting for meal intake when giving correction doses

By following this systematic approach to calculating correction insulin doses, you can help patients maintain optimal glycemic control while minimizing the risks of hypoglycemia.