What is the recommended dosing when converting a patient from Toujeo (insulin glargine) to Lantus (insulin glargine)?

Converting from Toujeo to Lantus: Dosing Recommendations

When converting from Toujeo (insulin glargine 300 U/mL) to Lantus (insulin glargine 100 U/mL), start Lantus at 80% of the Toujeo dose being discontinued. 1

FDA-Approved Conversion Protocol

The FDA label for Lantus provides explicit guidance for this conversion:

• Reduce the dose by 20% when switching from once-daily Toujeo to once-daily Lantus 1
• This dose reduction is necessary because Toujeo and Lantus are not bioequivalent despite containing the same active ingredient 2, 3
• Patients consistently require higher daily insulin doses with Toujeo compared to Lantus to achieve equivalent glycemic control 2, 3

Practical Example

• If a patient is taking 30 units of Toujeo daily, start Lantus at 24 units daily (30 × 0.80 = 24 units)
• If taking 50 units of Toujeo daily, start Lantus at 40 units daily (50 × 0.80 = 40 units)

Post-Conversion Monitoring Requirements

Intensive glucose monitoring is mandatory during the conversion period:

• Check fasting blood glucose daily for the first 1-2 weeks after conversion 4
• Adjust the Lantus dose every 3 days based on fasting glucose patterns 4
• Target fasting glucose of 80-130 mg/dL 5, 4

Titration Algorithm After Conversion

• If fasting glucose is 140-179 mg/dL: increase Lantus by 2 units every 3 days 4
• If fasting glucose is ≥180 mg/dL: increase Lantus by 4 units every 3 days 4
• If hypoglycemia occurs: reduce dose immediately by 10-20% and reassess 4

Why the Dose Reduction is Necessary

The pharmacokinetic and pharmacodynamic profiles differ significantly between these formulations:

• Toujeo has a flatter, more prolonged absorption profile lasting beyond 24 hours with less variability 2, 3
• Lantus has a shorter duration of action (approximately 24 hours) with a slightly more pronounced peak 2, 3
• The threefold higher concentration in Toujeo creates a smaller subcutaneous depot with slower, more gradual insulin release 2
• Clinical trials consistently show patients need higher total daily doses of Toujeo (typically 10-18% more) compared to Lantus for equivalent HbA1c reduction 2, 3

Critical Pitfalls to Avoid

• Never convert unit-for-unit (1:1) from Toujeo to Lantus—this will cause hypoglycemia 1, 2
• Do not dilute or mix Lantus with any other insulin or solution due to its low pH 1
• Do not delay dose adjustments if fasting glucose remains elevated—titrate every 3 days as needed 4
• Maintain the same injection time daily with Lantus, typically at bedtime or with the evening meal 4

Special Populations Requiring Additional Caution

Reduce the converted Lantus dose by an additional 10-20% beyond the standard 80% conversion for:

• Elderly patients (>65 years) 4
• Patients with renal impairment 4
• History of severe hypoglycemia 4
• Poor oral intake or acute illness 4

For these high-risk patients, consider starting at 60-70% of the Toujeo dose rather than 80%, then titrate upward cautiously based on glucose monitoring 4.