Insulin Glulisine Correction Factor
Use the 1800 rule to calculate the correction factor for insulin glulisine: divide 1800 by the patient's total daily insulin dose (TDD) to determine how many mg/dL one unit of insulin will lower blood glucose.
Calculation Method
The correction factor (also called insulin sensitivity factor) for glulisine follows the 1800 rule 1:
- Correction Factor (mg/dL) = 1800 ÷ Total Daily Dose (TDD)
For example, if a patient uses 60 units of insulin per day total, their correction factor would be 1800 ÷ 60 = 30 mg/dL per unit.
Important Considerations for Timing
Morning correction doses require more insulin than afternoon or evening doses 2. The 1800 rule accurately estimates morning correction needs but may overestimate insulin requirements for afternoon and evening corrections 2.
- The morning correction factor calculated by the 1800 rule is appropriate
- For afternoon and evening, you may need to use a higher correction factor (meaning less insulin per unit of glucose elevation)
- This diurnal variation occurs across all age groups and pubertal stages 2
Alternative Calculation Using ICR
If you know the patient's insulin-to-carbohydrate ratio (ICR), you can estimate the correction factor as approximately 5 × ICR 2. This relationship is highly reliable (R² = 0.95) and accounts for individual patient factors.
Factors Affecting Insulin Requirements
When determining the correction factor, recognize that the following increase insulin requirements and thus lower the correction factor 2:
- Higher body mass index
- Older age
- Advanced pubertal stage
- Longer diabetes duration
Clinical Pitfall
Do not use the same correction factor throughout the entire day. The 1800 rule works well for morning hyperglycemia correction but will cause you to give too much insulin if applied uniformly to afternoon and evening corrections 2. Consider using separate correction factors for different times of day, with the morning requiring the most aggressive correction.