What is the recommended dose of Humalog (insulin lispro) to initiate before meals in a patient with uncontrolled type 2 diabetes mellitus (DM) currently on Basaglar (glargine) 0.3 units/kg/day?

Initiating Prandial Insulin with Basal Insulin in Uncontrolled Type 2 Diabetes

Start Humalog at 4 units before each of the three main meals (breakfast, lunch, and dinner), which represents approximately 10% of your current basal dose, and titrate by 1-2 units every 3 days based on 2-hour postprandial glucose readings targeting <180 mg/dL. 1

Understanding Your Current Situation

Your patient is on Basaglar 0.3 units/kg/day, which is already at the critical threshold where adding prandial insulin becomes essential rather than continuing to escalate basal insulin alone. 1 When basal insulin exceeds 0.5 units/kg/day and approaches 1.0 units/kg/day, further increases lead to "overbasalization"—a dangerous pattern where excessive basal insulin masks the need for mealtime coverage, causing hypoglycemia between meals while postprandial glucose remains elevated. 1

Initial Humalog Dosing Algorithm

Starting Dose Options

• Standard approach: Begin with 4 units of Humalog before each of the three main meals 1
• Alternative calculation: Use 10% of the current basal insulin dose per meal 1
• For severe hyperglycemia (HbA1c ≥10-12%): Consider starting with 0.3-0.5 units/kg/day as total daily insulin dose, split 50% basal and 50% prandial (divided among three meals) 1

The 4-unit starting dose is preferred because it provides a safe, standardized approach that minimizes hypoglycemia risk while establishing effective mealtime coverage. 1

Timing of Administration

Humalog must be administered 0-15 minutes before meals, not after eating, to effectively manage postprandial glucose excursions. 1 The rapid-acting analog has an onset of action at 0.25-0.5 hours, peaks at 1-3 hours, and has a duration of 3-5 hours. 1

Titration Protocol

Adjustment Schedule

• Increase each meal's Humalog dose by 1-2 units (or 10-15%) every 3 days based on 2-hour postprandial glucose readings 1
• Target postprandial glucose <180 mg/dL 1
• If hypoglycemia occurs without clear cause, reduce the corresponding dose by 10-20% immediately 1

Monitoring Requirements

• Check pre-meal glucose immediately before each meal to guide correction doses 1
• Check 2-hour postprandial glucose after each meal to assess adequacy of prandial coverage 1
• Continue daily fasting glucose monitoring to ensure basal insulin remains appropriately dosed 1

Carbohydrate Coverage Considerations

While starting with fixed doses, you can transition to carbohydrate counting using the insulin-to-carbohydrate ratio (ICR):

• Formula: ICR = 450 ÷ total daily dose (TDD) 1
• Common starting ratio: 1 unit per 10-15 grams of carbohydrate 1

This allows more flexible meal planning once the patient demonstrates competency with basic insulin administration. 1

Foundation Therapy: Continue Metformin

Metformin must be continued at maximum tolerated dose (up to 2000-2550 mg daily) unless contraindicated, as this combination provides superior glycemic control with reduced insulin requirements and less weight gain compared to insulin alone. 1 The American Diabetes Association explicitly recommends continuing metformin when adding or intensifying insulin therapy. 1

Critical Pitfalls to Avoid

Never Use Sliding Scale as Monotherapy

Sliding scale insulin treats hyperglycemia reactively after it occurs rather than preventing it, leading to dangerous glucose fluctuations. 1, 2 All patients requiring insulin should be on a scheduled regimen with basal, prandial, and correction components—not correction insulin alone. 1 The RABBIT 2 trial demonstrated that basal-bolus therapy achieved target glucose <140 mg/dL in 66% of patients versus only 38% with sliding scale alone. 2

Avoid Overbasalization

Do not continue escalating Basaglar beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia, as this leads to increased hypoglycemia risk without improved control. 1 Clinical signals of overbasalization include basal dose >0.5 units/kg/day, bedtime-to-morning glucose differential ≥50 mg/dL, hypoglycemia episodes, and high glucose variability. 1

Never Give Rapid-Acting Insulin at Bedtime

Administering Humalog at bedtime significantly increases nocturnal hypoglycemia risk and should be avoided. 1 Rapid-acting insulin is designed for mealtime coverage only.

Expected Outcomes

With appropriate basal-bolus therapy at weight-based dosing, 68% of patients achieve mean blood glucose <140 mg/dL versus only 38% with inadequate insulin coverage. 1 The RABBIT 2 trial showed that basal-bolus insulin resulted in mean daily blood glucose differences of 23-58 mg/dL compared to sliding scale, with an overall difference of 27 mg/dL (p<0.01). 2

Randomized trials comparing premixed insulin to basal-bolus regimens show that properly implemented basal-bolus therapy provides better glycemic control with reduced hospital complications and no increase in hypoglycemia when appropriately dosed. 1

Patient Education Essentials

• Hypoglycemia recognition and treatment: Treat any glucose <70 mg/dL immediately with 15 grams of fast-acting carbohydrate, recheck in 15 minutes, and repeat if needed 1
• Proper injection technique and site rotation to ensure consistent absorption 1
• Self-monitoring of blood glucose: Pre-meal and 2-hour postprandial checks during titration 1
• "Sick day" management rules and when to contact healthcare provider 1
• Insulin storage and handling to maintain potency 1

Reassessment Schedule

• Adjust prandial doses every 3 days during active titration based on postprandial glucose patterns 1
• Reassess overall glycemic control and HbA1c every 3-6 months once stable 1
• If HbA1c remains above target after 3-6 months despite optimized basal-bolus therapy, consider adding a GLP-1 receptor agonist to improve control while minimizing weight gain and hypoglycemia risk 1