What adjustments should be made to the ISF, basal rate, or carb ratio on the T:slim (insulin pump) to prevent hypoglycemia?

Insulin Pump Parameter Adjustment for Hypoglycemia After Meal

Your insulin sensitivity factor (ISF) of 30 is too aggressive and should be increased to 40-50, and your carb ratio may need adjustment from 1:8 to 1:10 or 1:12 to prevent recurrent hypoglycemia.

Understanding the Problem

Your blood glucose dropped to 86 mg/dL despite eating 72 grams of carbs and taking 9 units of correction insulin, which indicates your correction dose was excessive. 1 This pattern suggests your ISF is set too aggressively, causing overcorrection of hyperglycemia. 1

Immediate ISF Adjustment Required

Your current ISF of 30 means 1 unit of insulin lowers your blood glucose by 30 mg/dL, which appears too strong based on this hypoglycemic episode. 1

• Increase your ISF to 40-50 initially (meaning 1 unit will lower blood glucose by 40-50 mg/dL instead of 30 mg/dL). 1
• This represents a 10-20% reduction in correction insulin potency, which aligns with standard dose reduction recommendations when hypoglycemia occurs. 2
• If correction doses consistently fail to bring glucose into target range or cause hypoglycemia, adjust the ISF rather than other parameters. 1

Carb Ratio Assessment

Your carb ratio of 1:8 means 1 unit covers 8 grams of carbs. For 72 grams, this would require 9 units of meal insulin. 1

• If you took 9 units as correction insulin (not meal insulin), this is the primary problem—you may have miscalculated or the pump settings are incorrect. 1
• Consider adjusting your carb ratio to 1:10 or 1:12, which would reduce meal insulin from 9 units to 7.2 or 6 units for the same 72 grams of carbs. 1
• Change the insulin-to-carbohydrate ratio if glucose after meals is consistently out of target. 3

Basal Rate Evaluation

Your basal rate of 1.3 units/hour may be appropriate, but this hypoglycemic episode occurred postprandially, suggesting the issue is with bolus parameters (ISF and carb ratio) rather than basal insulin. 1

• For pump therapy, approximately 40-60% of total daily dose should be basal delivery, with the remainder as mealtime and correction boluses. 3
• Do not adjust basal rates based on postprandial hypoglycemia—this reflects bolus insulin miscalculation. 1

Systematic Adjustment Protocol

Follow this algorithmic approach:

1. Increase ISF from 30 to 40-50 immediately to reduce correction insulin potency by 10-20%. 1, 2
2. Test the new ISF by monitoring correction doses over 3-7 days to ensure they bring glucose into target (80-130 mg/dL) without causing hypoglycemia. 2, 1
3. Reassess carb ratio if postprandial glucose patterns remain problematic after ISF adjustment—consider changing from 1:8 to 1:10. 1, 3
4. Monitor fasting glucose to confirm basal rate adequacy (target 80-130 mg/dL)—only adjust basal if fasting glucose is consistently out of range. 2, 1

Critical Monitoring Requirements

• Increase blood glucose monitoring frequency to at least 4-6 times daily during parameter adjustments to detect patterns requiring further modification. 3
• Reassess ISF and carb ratio parameters every 3-6 months or when significant changes in weight, activity, or overall insulin requirements occur. 3
• If hypoglycemia occurs without clear cause, reduce the problematic parameter by 10-20% immediately. 2, 1

Common Pitfalls to Avoid

• Do not adjust multiple parameters simultaneously—change ISF first, observe for 3-7 days, then adjust carb ratio if needed. 1, 3
• Do not blame basal insulin for postprandial hypoglycemia—this reflects bolus miscalculation, not basal rate issues. 1
• Avoid treating hypoglycemia with protein-rich foods—use 15 grams of pure glucose or fast-acting carbohydrates for optimal correction. 2
• Do not continue using aggressive ISF settings that repeatedly cause hypoglycemia—this creates a vicious cycle of recurrent hypoglycemia and impaired counterregulation. 4, 5

Hypoglycemia Prevention Strategy

• Scrupulous avoidance of hypoglycemia for 2-3 weeks can reverse hypoglycemia unawareness if present. 2, 4
• Treat hypoglycemia at blood glucose ≤70 mg/dL with 15 grams of fast-acting carbohydrate. 2
• Recognize that recurrent hypoglycemia shifts glycemic thresholds lower, making future episodes harder to detect. 4, 6