What is the recommended dosing of Novolog (insulin aspart) for a patient with diabetes based on carb intake and using a sliding scale, considering individual insulin sensitivity and renal function?

Novolog Dosing for Carbohydrate Intake and Sliding Scale

Carbohydrate-Based Dosing (Insulin-to-Carbohydrate Ratio)

For carbohydrate counting, use the 450 or 500 rule to calculate your insulin-to-carbohydrate ratio (ICR), then dose Novolog 0-15 minutes before meals based on the grams of carbohydrate you plan to eat. 1, 2

Calculating Your Insulin-to-Carbohydrate Ratio

• Formula: ICR = 450 ÷ Total Daily Dose (TDD) for rapid-acting insulin analogs like Novolog 2
• Alternative formula: ICR = 500 ÷ TDD for regular insulin (use 450 for Novolog as it's rapid-acting) 2
• A common starting ratio is 1 unit per 10-15 grams of carbohydrate if you don't know your TDD 2
• Example: If your TDD is 45 units, your ICR = 450 ÷ 45 = 10, meaning 1 unit of Novolog covers 10 grams of carbohydrate 2

Practical Application

• Count the total carbohydrates in your meal (read nutrition labels, use apps, or reference guides) 2
• Divide total carbs by your ICR to get your meal dose 2
• Example: 60 grams of carbohydrate ÷ 10 (your ICR) = 6 units of Novolog 2
• Timing: Administer Novolog 0-15 minutes before starting your meal for optimal postprandial control 3, 4, 5

Adjusting Your Ratio

• If your 2-hour post-meal glucose is consistently >180 mg/dL, decrease your ICR number (give more insulin per carb) 2
• If you experience post-meal hypoglycemia, increase your ICR number (give less insulin per carb) 2
• Adjust by 1-2 units or 10-15% every 3 days based on postprandial glucose patterns 1, 2

Correction Dose (Sliding Scale) for High Blood Sugar

Use the insulin sensitivity factor (ISF) to calculate correction doses when your pre-meal glucose is above target, adding this to your carbohydrate dose. 2

Calculating Your Insulin Sensitivity Factor

• Formula: ISF = 1500 ÷ Total Daily Dose (TDD) 2
• This tells you how many mg/dL one unit of Novolog will lower your glucose 2
• Example: If your TDD is 50 units, ISF = 1500 ÷ 50 = 30, meaning 1 unit lowers glucose by 30 mg/dL 2

Applying Correction Doses

• Target pre-meal glucose: 90-150 mg/dL 2, 6
• Correction formula: (Current glucose - Target glucose) ÷ ISF = correction units 2
• Example: Current glucose 220 mg/dL, target 120 mg/dL, ISF 30 → (220-120) ÷ 30 = 3.3 units (round to 3 units) 2
• Add correction dose to your carbohydrate dose for total pre-meal insulin 2

Simplified Sliding Scale (When Not Carb Counting)

If you're not counting carbohydrates, use this stepped approach for correction only:

• Pre-meal glucose >250 mg/dL: Add 2 units of Novolog 2, 6
• Pre-meal glucose >350 mg/dL: Add 4 units of Novolog 2, 6

Critical warning: This simplified approach should be used only as an adjunct to scheduled basal and prandial insulin, never as monotherapy, as sliding scale alone is explicitly condemned by all major diabetes guidelines and leads to dangerous glucose fluctuations 2, 6

Special Considerations for Renal Impairment

• Renal impairment does not significantly alter Novolog pharmacokinetics based on creatinine clearance studies 3
• However, insulin clearance decreases with declining kidney function, requiring closer monitoring for hypoglycemia 7, 2
• For CKD Stage 5 with type 2 diabetes: Reduce total daily insulin dose by 50% 2
• For CKD Stage 5 with type 1 diabetes: Reduce total daily insulin dose by 35-40% 2
• Titrate conservatively in patients with eGFR <45 mL/min/1.73 m² to avoid hypoglycemia 7

Critical Safety Principles

• Never use Novolog at bedtime to avoid nocturnal hypoglycemia—use long-acting basal insulin instead 2, 6
• Avoid "insulin stacking": Wait at least 3-4 hours between correction doses, as insulin from the previous dose may still be active 2
• Treat hypoglycemia immediately (glucose ≤70 mg/dL) with 15-20 grams of fast-acting carbohydrate 1, 8
• Recalculate your ICR and ISF periodically (every few weeks to months) as your total daily dose changes, not daily 2
• If correction doses consistently fail to bring glucose into target range, adjust your ISF, not your basal insulin dose 2

When to Seek Provider Guidance

• If you require frequent correction doses (more than 2-3 times daily), your basal insulin or meal doses need adjustment 2
• If your basal insulin exceeds 0.5 units/kg/day and you're still having high post-meal glucose, you need prandial insulin optimization, not more corrections 1, 2
• Recurrent hypoglycemia signals the need for immediate dose reduction by 10-20% 1, 2