What is the recommended dose conversion when switching from Lantus (insulin glargine) to Toujeo (insulin glargine U300)?

Converting from Lantus to Toujeo: Dose Adjustment Required

When switching from Lantus (insulin glargine 100 U/mL) to Toujeo (insulin glargine 300 U/mL), increase the dose by approximately 20% because the two formulations are not bioequivalent. 1, 2

Key Conversion Principle

The FDA-approved conversion requires a dose adjustment in the opposite direction of what you might expect:

• When converting FROM Toujeo TO Lantus: Use 80% of the Toujeo dose 1
• When converting FROM Lantus TO Toujeo: This means you need approximately 120% (or 1.25x) of your Lantus dose to achieve equivalent glycemic control 2, 3

The reason for this counterintuitive increase is that Toujeo and Lantus are not bioequivalent despite containing the same insulin molecule 2. Toujeo's more concentrated formulation (300 U/mL vs 100 U/mL) creates a smaller subcutaneous depot with a flatter, more prolonged absorption profile that requires higher total daily units to achieve the same glucose-lowering effect 4, 2.

Practical Conversion Algorithm

Step 1: Calculate the New Toujeo Dose

• Take the current total daily Lantus dose
• Multiply by 1.2 (or add 20%) to get the starting Toujeo dose 2, 3
• Example: If on Lantus 30 units daily → Start Toujeo at 36 units daily

Step 2: Timing Considerations

• Administer Toujeo once daily at the same time each day 1
• Toujeo provides glucose-lowering activity exceeding 24 hours, offering more flexibility in injection timing than Lantus 4, 2

Step 3: Intensive Monitoring Period

• Check blood glucose at least 4 times daily during the first 1-2 weeks after conversion 5, 1
• Monitor fasting glucose daily to assess adequacy of basal coverage 6
• Increase frequency of blood glucose monitoring during any insulin regimen change 1

Step 4: Dose Titration Post-Conversion

• Adjust dose by 2-4 units (or 10-15%) every 3 days based on fasting glucose values 7, 5
• Target fasting plasma glucose: 80-130 mg/dL 7
• If hypoglycemia occurs, reduce dose immediately by 10-20% 7, 6

Clinical Advantages of Toujeo Over Lantus

While requiring higher daily doses, Toujeo offers several benefits:

• Lower risk of nocturnal hypoglycemia in insulin-experienced patients with type 2 diabetes 4, 3
• Flatter and more prolonged pharmacokinetic profile with duration exceeding 24 hours 4, 2
• Less intra- and inter-patient variability, making glucose control more reproducible 2
• Slightly less weight gain compared to Lantus 2
• Greater flexibility in injection timing due to extended duration of action 2

Critical Pitfalls to Avoid

• Do NOT convert unit-for-unit from Lantus to Toujeo—this will result in inadequate glycemic control 1, 2, 3
• Do not dilute or mix Toujeo with any other insulin or solution 1
• Do not administer intravenously or via an insulin pump 1
• Avoid injecting into areas of lipodystrophy or localized cutaneous amyloidosis, as this can cause unpredictable absorption and hyperglycemia 1
• Do not delay dose adjustments—titrate every 3 days based on fasting glucose to reach targets efficiently 7

Special Considerations

For Patients at High Risk of Hypoglycemia

• Consider a more conservative initial increase (10-15% rather than 20%) in elderly patients, those with renal impairment, or history of severe hypoglycemia 6
• Monitor even more intensively during the conversion period 1

Prandial Insulin Adjustments

• Continue the same prandial insulin doses initially 1
• Adjust prandial insulin separately based on postprandial glucose readings, not as part of the basal conversion 7

Expected Insulin Requirements

• Clinical trials consistently show that patients on Toujeo require 10-20% higher daily basal insulin doses than those on Lantus to achieve comparable HbA1c reduction 4, 3
• This higher dose requirement is expected and does not indicate treatment failure 2, 3