About This Conversion
The Toujeo → Lantus Conversion Calculator provides a recommended starting dose for patients switching from Toujeo® (insulin glargine 300 units/mL) to Lantus® (insulin glargine 100 units/mL). The conversion is based on a conservative 20% dose reduction, a standard clinical practice designed to mitigate the risk of hypoglycemia when moving from a more concentrated to a less concentrated basal insulin.
Outputs Explained
The tool calculates and displays the following key information:
- Recommended Initial Lantus Dose: This is the primary output, representing 80% of the patient’s total daily Toujeo dose, rounded to the nearest whole unit. This is a starting dose only.
- Calculation Formula: The tool shows the exact math used: (Total Daily Toujeo Dose) × 0.80 = Initial Daily Lantus Dose.
- High-Dose Alert: If a very high Toujeo dose is entered (e.g., over 200 units), a note may appear prompting the user to double-check the accuracy of the input value.
How to Use the Calculator
Using this clinical tool is a straightforward process for healthcare professionals:
- Enter Toujeo Dose: In the designated input field, type the patient’s current total daily dose of Toujeo in units.
- Calculate: Click the “Calculate” button to process the information.
- Review Results: The recommended starting dose for Lantus will be displayed instantly, along with the calculation details. This result should be used as a component of a comprehensive clinical assessment.
Dosing Overview
Both Toujeo and Lantus are long-acting “basal” insulins containing insulin glargine, but they have different concentrations. Lantus is a 100 units/mL (U-100) formulation, while Toujeo is a more concentrated 300 units/mL (U-300) formulation. This higher concentration gives Toujeo a more gradual release and a longer duration of action in some patients compared to Lantus. Due to these pharmacokinetic differences, a direct unit-for-unit conversion is not recommended; a dose reduction is the standard of care to ensure patient safety.
Switching Protocol
When switching a patient from Toujeo to Lantus, the calculated dose is only the first step. The following protocol is essential:
- Administration Timing: The new Lantus dose should be administered once daily, at the same time the patient was previously taking their Toujeo dose.
- Blood Glucose Monitoring: Advise the patient to monitor their blood glucose levels more frequently, especially during the first week after the switch, to identify any trends of hyperglycemia or hypoglycemia.
- Dose Titration: Subsequent adjustments to the Lantus dose are expected. Titration should be based on the patient’s monitored blood glucose levels, glycemic targets, and overall clinical picture.
Missed Dose Information
If a patient misses their dose of long-acting insulin like Lantus, they should be advised to contact their healthcare provider for instructions. General guidance often includes taking the missed dose as soon as remembered, but not if it is almost time for the next scheduled dose. Patients should be explicitly warned not to take a double dose to make up for a missed one, as this can lead to severe hypoglycemia.
Safety Alerts
Primary Risk: Hypoglycemia
The most significant risk when switching from Toujeo to Lantus is hypoglycemia (low blood sugar). The 20% dose reduction is a proactive measure to minimize this risk. Clinicians must educate patients on the signs and symptoms of hypoglycemia, which can include:
- Shakiness or nervousness
- Sweating, chills, and clamminess
- Irritability or impatience
- Confusion
- Rapid heartbeat
- Dizziness or lightheadedness
This calculator is intended for use by licensed healthcare professionals. All calculations must be verified with clinical judgment and consideration of individual patient factors before application.
Frequently Asked Questions
Why is the dose reduced by 20% when switching from Toujeo to Lantus?
The 20% dose reduction is a conservative safety measure. Toujeo (U-300) has a different absorption and duration profile than Lantus (U-100). A unit-for-unit switch could result in a higher effective insulin level initially, increasing the risk of hypoglycemia. The 80% starting dose provides a safer entry point for titration.
Can I use this calculator to switch from Lantus to Toujeo?
No. This tool is for Toujeo-to-Lantus conversion only. The recommended conversion from Lantus to Toujeo is typically a 1-to-1 unit conversion, though some guidelines suggest starting at 80% of the Lantus dose if the patient is well-controlled. Always refer to official prescribing information.
What should a patient do if their blood sugar is too high or low after switching?
The patient should follow their personalized plan for managing high or low blood sugar and contact their healthcare provider immediately. The Lantus dose will likely need adjustment (titration) based on these readings.
Is the calculated Lantus dose a final dose?
No, it is a starting dose only. It is very likely that the dose will need to be adjusted up or down in the days and weeks following the switch based on blood glucose monitoring.
Should the new Lantus dose be administered at the same time as the old Toujeo dose?
Yes. To maintain consistent basal insulin coverage, the first dose of Lantus should be given at the same time the next dose of Toujeo would have been due.
Does this tool account for factors like kidney function or A1c?
No. The calculator performs a standard mathematical conversion. It is the responsibility of the clinician to consider all patient-specific factors, including renal/hepatic function, recent A1c, risk of hypoglycemia, and lifestyle changes, when determining the final appropriate dose.
Does this calculator work for Toujeo Max SoloStar and Lantus SoloStar pens?
Yes. The calculation is based on the total daily units of insulin, regardless of the injection device used (e.g., SoloStar pen, vial, etc.). The final dose must still be deliverable by the chosen device.
What if a patient is taking their Toujeo dose split into two injections?
The calculator requires the total daily dose. You should add the amounts from any split doses together to get the correct total daily input value.
References
- Toujeo® (insulin glargine) injection [Prescribing Information]. U.S. Food and Drug Administration. Bridgewater, NJ: Sanofi-Aventis U.S. LLC.
- Lantus® (insulin glargine) injection [Prescribing Information]. U.S. Food and Drug Administration. Bridgewater, NJ: Sanofi-Aventis U.S. LLC.
- El-Sayed NA, Aleppo G, Aroda VR, et al. 9. Pharmacologic Approaches to Glycemic Treatment: Standards of Care in Diabetes—2023. Diabetes Care. 2023;46(Suppl 1):S140-S157. doi:10.2337/dc23-S009
- Sutton G, Minguet J, G-M, Dahli T, A, K. A Review of the Evidence for the Pharmacokinetic and Pharmacodynamic Properties of Concentrated Insulins. Diabetes Ther. 2018;9(4):1333-1355. doi:10.1007/s13300-018-0435-0
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