What is the recommended starting dose of Lantus (insulin glargine) for a patient switching from Novolog 70/30 (insulin aspart protamine/insulin aspart) 15 units, 1-2 times a day?

Converting from Novolog 70/30 to Lantus: Dosing Strategy

For a patient taking Novolog 70/30 15 units 1-2 times daily (total daily dose 15-30 units), start Lantus at 8-12 units once daily, which represents approximately 80% of the basal component of the current premixed insulin regimen. 1, 2

Calculating the Starting Dose

The basal component of 70/30 insulin represents approximately 70% of the total daily dose 2:

• If taking 15 units once daily: Basal component = 10.5 units → Start Lantus at 8 units once daily (80% of basal component) 1, 2
• If taking 15 units twice daily (30 units total): Basal component = 21 units → Start Lantus at 12 units once daily (80% of basal component) 1, 2

The 20% reduction from the calculated basal component prevents hypoglycemia during the transition, particularly important given the variable dosing pattern 2.

Critical Gap: Loss of Prandial Coverage

This conversion creates a significant therapeutic gap because Novolog 70/30 provides both basal AND prandial insulin coverage, while Lantus provides only basal coverage. 2 The 30% rapid-acting component (4.5-9 units daily) will be lost in this transition.

Addressing the Prandial Gap

You have three options:

• Add rapid-acting insulin before meals: Start with 4 units of rapid-acting insulin (lispro, aspart, or glulisine) before the largest meal, or use 10% of the basal dose 1, 2
• Intermediate step: Add rapid-acting insulin before only the largest meal initially, then expand to other meals if needed 2
• Monitor closely: If the patient's A1C is near target and postprandial glucose remains acceptable, you may defer adding prandial insulin 2

Titration Protocol

Increase Lantus by 2 units every 3 days if fasting glucose is 140-179 mg/dL, or by 4 units every 3 days if fasting glucose is ≥180 mg/dL, targeting fasting glucose of 80-130 mg/dL. 1, 3

If hypoglycemia occurs without clear cause, reduce the dose by 10-20% immediately 1, 3

Critical Threshold Warning

When Lantus exceeds 0.5 units/kg/day (approximately 35-40 units for an average adult), stop escalating basal insulin and add prandial insulin instead. 1 Continuing to increase basal insulin beyond this threshold leads to "overbasalization" with increased hypoglycemia risk and suboptimal control 1.

Clinical signals of overbasalization include:

• Basal dose >0.5 units/kg/day
• Bedtime-to-morning glucose differential ≥50 mg/dL
• Hypoglycemia episodes
• High glucose variability 1

Monitoring Requirements

• Daily fasting blood glucose monitoring during titration 1, 3
• Pre-meal and 2-hour postprandial glucose if prandial insulin is added 1
• Reassess every 3 days during active titration 1
• Check HbA1c every 3 months to assess overall glycemic control 1

Common Pitfalls to Avoid

• Never use 1:1 unit conversion from total 70/30 dose to Lantus—this causes severe hypoglycemia 2
• Don't rely on sliding scale insulin alone as prandial replacement—this reactive approach leads to poor glycemic control 2
• Don't forget to continue metformin (unless contraindicated) when initiating basal insulin 1, 3
• Don't delay adding prandial insulin if postprandial glucose remains elevated or HbA1c stays above target after 3-6 months 1

Patient Education Essentials

Provide comprehensive education on:

• Self-monitoring of blood glucose, particularly fasting and pre-meal values 2
• Recognition and treatment of hypoglycemia with 15 grams of fast-acting carbohydrate 1, 2
• Proper injection technique and site rotation 1
• Dietary considerations now that prandial coverage has changed 2