How do I incorporate correction doses using the insulin sensitivity factor into a basal-bolus insulin regimen for a 70 kg patient with type 2 diabetes mellitus (T2DM) who is eating orally?

Incorporating Correction Doses Using Insulin Sensitivity Factor in Basal-Bolus Regimens

You are correct—a complete basal-bolus insulin regimen for a 70 kg patient with T2DM eating orally must include correction doses calculated using the insulin sensitivity factor (ISF), in addition to basal insulin and carbohydrate coverage. Here is the proper approach:

Complete Basal-Bolus Insulin Calculation with Correction Doses

Step 1: Calculate Total Daily Dose (TDD)

• For a 70 kg patient with T2DM requiring basal-bolus therapy, start with 0.5 units/kg/day as TDD = 35 units/day total 1
• Divide as 50% basal insulin (17-18 units glargine once daily) and 50% prandial insulin (17-18 units total, split among meals) 1, 2

Step 2: Distribute Prandial Insulin

• Split the 17-18 units of prandial insulin evenly: approximately 6 units of rapid-acting insulin before each meal (breakfast, lunch, dinner) 1
• This provides the base mealtime coverage before applying carbohydrate ratios 1

Step 3: Calculate Insulin-to-Carbohydrate Ratio (ICR)

• Use the formula: ICR = 450 ÷ TDD for rapid-acting analogs 1
• For this patient: 450 ÷ 35 = approximately 1:13 (1 unit covers 13 grams of carbohydrate) 1
• Adjust the 6-unit base dose up or down based on actual carbohydrate intake using this ratio 1

Step 4: Calculate Insulin Sensitivity Factor (ISF) for Correction Doses

• Use the formula: ISF = 1500 ÷ TDD 1
• For this patient: 1500 ÷ 35 = approximately 43 mg/dL 1
• This means 1 unit of rapid-acting insulin will lower blood glucose by approximately 43 mg/dL 1

Step 5: Apply Correction Dose Formula

• Correction dose = (Current BG - Target BG) ÷ ISF 3, 1
• Set target blood glucose at 125 mg/dL (midpoint of 80-130 mg/dL fasting target range) 3, 1

Complete Worked Example with Correction Dose

If the patient has a pre-meal blood glucose of 250 mg/dL and plans to eat 60 grams of carbohydrates:

Carbohydrate Coverage:

• 60 g ÷ 13 (ICR) = 4.6 units (round to 5 units for carbohydrate coverage) 3

Correction Dose:

• (250 - 125) ÷ 43 (ISF) = 125 ÷ 43 = 2.9 units (round to 3 units for correction) 3, 1

Total Prandial Bolus:

• 5 units (carb coverage) + 3 units (correction) = 8 units of rapid-acting insulin before this meal 3

Critical Timing and Administration Points

• Administer rapid-acting insulin 0-15 minutes before meals for optimal postprandial glucose control 1, 4
• Never give rapid-acting insulin at bedtime to avoid nocturnal hypoglycemia 1
• Basal insulin (glargine) is given once daily at the same time each day, independent of meals 1

Titration of ISF Over Time

• If correction doses consistently fail to bring glucose into target range, adjust the ISF (not the basal dose) 1
• If correction doses cause hypoglycemia, increase the ISF number (e.g., from 43 to 50-60), making each unit less potent 1
• Recalculate ISF periodically (every few weeks to months) as TDD changes with dose adjustments 1

Common Pitfalls to Avoid

• Do not use sliding scale insulin alone as monotherapy—it treats hyperglycemia reactively rather than preventing it, leading to dangerous glucose fluctuations 3, 1
• Do not "stack" correction doses—wait at least 3-4 hours between correction doses, as insulin from the previous dose may still be active 1
• Do not blame missed carbohydrate coverage for fasting hyperglycemia—fasting glucose reflects basal insulin adequacy, not meal coverage 1
• Do not continue escalating basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia with proper prandial and correction insulin 1

Monitoring Requirements

• Check pre-meal blood glucose immediately before each meal to calculate correction doses 3, 1
• Check 2-hour postprandial glucose to assess adequacy of carbohydrate coverage and adjust ICR if needed 1
• Daily fasting blood glucose monitoring is essential to titrate basal insulin 1