Lantus 100 to Lantus 300 Dose Conversion
When switching from 40 units of Lantus 100 Solostar to Lantus 300 Solostar (Toujeo), start with 40 units of Toujeo and expect to increase the dose by approximately 10-18% (4-7 units) over subsequent titrations to achieve equivalent glycemic control.
Understanding the Conversion
- Toujeo (insulin glargine U-300) is three times more concentrated than Lantus (insulin glargine U-100), but this does NOT mean you divide the dose by three 1.
- U-300 glargine has modestly lower efficacy per unit administered compared to U-100 glargine, requiring dose adjustments when switching between formulations 1.
- The initial conversion is unit-to-unit (40 units of Lantus 100 = 40 units of Toujeo initially), but patients typically require approximately 10-18% higher daily doses of U-300 compared to U-100 to achieve equivalent glycemic control 2.
Practical Conversion Algorithm
Initial Dose
- Start with 40 units of Toujeo once daily at the same time the patient was taking Lantus 100 2.
- Administer at a consistent time each day to maintain stable blood glucose levels 2.
Expected Dose Titration
- Plan to increase the Toujeo dose by 4-7 units (10-18% of 40 units) over the following weeks based on fasting glucose monitoring 2.
- Increase by 2 units every 3 days if fasting glucose is 140-179 mg/dL 3.
- Increase by 4 units every 3 days if fasting glucose is ≥180 mg/dL 3.
- Target fasting plasma glucose of 80-130 mg/dL 3.
Key Advantages of Toujeo
- Toujeo provides a longer duration of action than Lantus 100, offering more stable 24-hour coverage with a flatter pharmacokinetic profile 1.
- The more stable and prolonged profile may reduce glucose variability 1.
- Concentrated formulations like U-300 glargine are particularly useful for patients requiring larger doses, as they deliver higher insulin amounts in smaller injection volumes 2.
Critical Safety Considerations
- Improper conversion between insulin concentrations can lead to significant dosing errors and potential hypoglycemia 1.
- Daily fasting blood glucose monitoring is essential during the conversion and titration phase 3.
- If hypoglycemia occurs without clear cause, reduce the dose by 10-20% immediately 3.
- Do not dilute or mix insulin glargine with any other insulin or solution due to its low pH 3.
Monitoring Requirements
- Check fasting glucose daily during the conversion period 3.
- Reassess the dose every 3 days during active titration 3.
- Monitor for signs of inadequate basal coverage, such as persistent fasting hyperglycemia or significant postprandial excursions 3.
- If the patient requires doses exceeding 0.5 units/kg/day and A1C remains above target after 3-6 months, consider adding prandial insulin or a GLP-1 receptor agonist rather than continuing to escalate basal insulin alone 3, 2.