What is the recommended dose of Lantus (insulin glargine) when switching from 30 units (U) of Toujeo (insulin glargine U300)?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: September 25, 2025View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

Switching from Toujeo 30 Units to Lantus: Dosing Recommendations

When switching from 30 units of Toujeo (insulin glargine U300) to Lantus (insulin glargine U100), the recommended starting dose of Lantus should be 80% of the Toujeo dose, which would be 24 units of Lantus.

Rationale for Dose Adjustment

The FDA-approved labeling for insulin glargine specifically addresses this conversion, stating that when switching from once-daily Toujeo (insulin glargine 300 units/mL) to once-daily Lantus (insulin glargine 100 units/mL), the recommended starting Lantus dosage should be 80% of the Toujeo dosage that is being discontinued 1.

This dose reduction is necessary because:

  • Toujeo (U300) and Lantus (U100) are not bioequivalent and have different pharmacokinetic profiles
  • Toujeo has a flatter and longer duration of action compared to Lantus 2
  • Patients typically require a higher daily insulin dose with Toujeo compared to Lantus to achieve equivalent glycemic control 3

Implementation Process

  1. Initial conversion: Calculate 80% of current Toujeo dose

    • 30 units Toujeo × 0.8 = 24 units Lantus
  2. Administration timing:

    • Administer Lantus at the same time of day as the previous Toujeo dose
    • Maintain consistency in the timing of daily injections 1
  3. Blood glucose monitoring:

    • Increase frequency of blood glucose monitoring during the transition period
    • Monitor fasting blood glucose levels closely for the first several days 1
  4. Dose titration:

    • Adjust Lantus dose based on fasting blood glucose readings
    • Increase dose by 2 units if 50% of fasting glucose readings are above target over a week
    • Decrease dose by 2 units if experiencing hypoglycemia or if >2 fasting glucose readings per week are <80 mg/dL 4
    • Target fasting glucose range: 90-150 mg/dL (may be adjusted based on individual health status and goals) 4

Special Considerations

  • Hypoglycemia risk: The transition period carries an increased risk of hypoglycemia due to the change in insulin pharmacokinetics 1
  • Patient education: Ensure the patient understands the difference between the two insulins and the importance of not confusing the two products 1
  • Concomitant medications: Maintain metformin if the patient is already taking it; consider adjustments to other diabetes medications as needed 5

Monitoring for Success

  • Evaluate the effectiveness of the transition after 1-2 weeks
  • Consider further dose adjustments based on:
    • Fasting blood glucose patterns
    • Occurrence of any hypoglycemic episodes
    • Overall glycemic control

This approach aligns with current guidelines for insulin management and specifically addresses the transition between these two formulations of insulin glargine, prioritizing patient safety while maintaining effective glycemic control.

References

Research

[INSULIN GLARGINE 300 U/mL (TOUJEO®)].

Revue medicale de Liege, 2016

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Guideline

Insulin Therapy

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.