For a patient on 66 units of insulin glargine (Lantus, U‑100), should the initial dose of insulin glargine (Toujeo, U‑300) also be 66 units?

Toujeo Dose Conversion from Lantus

When switching from 66 units of Lantus (U-100 insulin glargine) to Toujeo (U-300 insulin glargine), you should start with approximately 73–78 units of Toujeo, representing a 10–18% dose increase. The two formulations are not bioequivalent unit-for-unit, and Toujeo has modestly lower efficacy per unit administered, requiring higher daily doses to achieve equivalent glycemic control 1.

Why the Dose Must Be Increased

• U-300 glargine (Toujeo) requires approximately 10–18% higher daily doses compared to U-100 glargine (Lantus) to achieve the same glycemic control 1, 2.
• The two formulations are not bioequivalent—Toujeo has a more concentrated formulation that results in a smaller subcutaneous depot with slower, more prolonged absorption 3, 4.
• Meta-analysis of 15 randomized controlled trials (n=9,304 patients) demonstrated that patients on Toujeo required statistically significantly more units of insulin daily than those on Lantus to achieve equivalent HbA1c reduction 5.

Specific Conversion Recommendation

For a patient on 66 units of Lantus:

• Initial Toujeo dose: 73 units (10% increase) to 78 units (18% increase)
• Start with the lower end (73 units) if the patient has good glycemic control and low hypoglycemia risk
• Start with the higher end (78 units) if fasting glucose is frequently elevated or the patient has been experiencing hyperglycemia

Titration After Conversion

• Monitor fasting glucose daily for the first 2–4 weeks after switching 6
• Increase Toujeo by 2 units every 3 days if fasting glucose is 140–179 mg/dL 6
• Increase Toujeo by 4 units every 3 days if fasting glucose is ≥180 mg/dL 6
• Target fasting glucose: 80–130 mg/dL 6
• If hypoglycemia occurs, reduce dose by 10–20% immediately 6

Clinical Advantages of Toujeo Over Lantus

• Longer duration of action exceeding 24 hours with a flatter, more prolonged pharmacokinetic profile 1, 4
• Significantly lower rate of clinically significant hypoglycemia (<54 mg/dL) compared to Lantus in head-to-head trials (0% vs 6.0%, p=0.023) 2
• Reduced nocturnal hypoglycemia, particularly in insulin-experienced patients with type 2 diabetes 5, 7
• More stable and reproducible glucose-lowering activity with less intra- and inter-patient variability 3
• Greater flexibility in injection timing due to the extended duration of action 3

Critical Pitfalls to Avoid

• Do not use a 1:1 unit conversion—this will result in inadequate glycemic control because Toujeo requires 10–18% more units 1, 2
• Do not switch formulations without medical supervision and appropriate dose adjustment, as the products are not interchangeable unit-for-unit 6
• Do not delay dose titration—if fasting glucose remains elevated after 1–2 weeks, increase the dose systematically rather than waiting 6
• Do not mix or dilute Toujeo with any other insulin or solution 6

When Toujeo Is Particularly Advantageous

• Patients experiencing recurrent nocturnal hypoglycemia on Lantus should be switched to Toujeo for its superior hypoglycemia safety profile 1, 7
• Patients with significant glucose variability may achieve more stable control with Toujeo's longer duration of action 1
• Patients requiring large insulin doses benefit from the reduced injection volume with U-300 concentration 2

Monitoring Requirements

• Daily fasting glucose checks during the first 2–4 weeks after conversion 6
• Reassess HbA1c after 3 months to confirm equivalent or improved glycemic control 6
• Watch for signs of overbasalization if dose exceeds 0.5 units/kg/day: bedtime-to-morning glucose differential ≥50 mg/dL, hypoglycemia, or high glucose variability 1