What should the Insulin Sensitivity Factor (ISF) rate be if the current 1:10 ratio requires an additional 12 units of insulin?

Adjusting Insulin Sensitivity Factor (ISF) on Insulin Pump

The ISF should be adjusted to 1:5 (meaning 1 unit of insulin will lower blood glucose by 5 mg/dL) based on the current 1:10 ratio requiring an additional 12 units.

Understanding ISF Calculation and Adjustment

ISF is a critical parameter in insulin pump therapy that determines how much 1 unit of insulin will lower blood glucose. When the current setting is insufficient (requiring additional insulin), the ISF needs to be adjusted to be more aggressive.

Mathematical Approach to ISF Adjustment

The current situation indicates:

• Current ISF = 1:10 (1 unit lowers glucose by 10 mg/dL)
• Additional 12 units needed for correction

This suggests the current ISF is set too conservatively (not enough insulin per unit of blood glucose). The calculation for the new ISF is:

1. Current correction = Blood glucose ÷ 10
2. Actual correction needed = Current correction + 12 units
3. New ISF = Blood glucose ÷ (Current correction + 12)

Since the current ISF requires an additional 12 units, we can determine that the ISF should be approximately half as strong (1:5 instead of 1:10).

Factors Affecting ISF Settings

Research shows that ISF varies based on several factors:

• Time of day: ISF shows diurnal variation with higher correction dose requirements in the morning than later in the day 1
• Age: Older children require more insulin with lower ISF values 2
• Body mass index: Higher BMI is associated with lower ISF 1
• Insulin-to-carbohydrate ratio (ICR): ISF is strongly correlated with ICR 1

Practical Implementation

1. Change the ISF setting on the insulin pump from 1:10 to 1:5
2. Monitor blood glucose frequently after implementing the change (at least 4 times daily) to assess effectiveness
3. Document correction boluses and their effects on blood glucose levels
4. Adjust as needed based on observed responses over 3-7 days

Potential Risks and Monitoring

• Hypoglycemia risk: A more aggressive ISF (1:5) increases the risk of hypoglycemia, so careful monitoring is essential
• Blood glucose variability: Watch for increased glucose excursions that might indicate over-correction
• Nocturnal hypoglycemia: Be particularly cautious with correction boluses before bedtime

Additional Considerations

• Insulin stacking: Most modern insulin pumps account for "insulin on board" to prevent stacking of correction doses
• Temporary adjustments: Consider temporary ISF adjustments for illness, exercise, or stress
• Regular reassessment: ISF should be reassessed every 3 months or with significant weight changes

This adjustment should significantly improve glycemic control by providing more appropriate correction doses for elevated blood glucose levels.