Equivalent Dose of Insulin Glargine for 23 Units of Insulin Degludec
When converting from 23 units of insulin degludec (Tresiba) to insulin glargine (Lantus), initiate glargine at 23 units once daily using a 1:1 unit-for-unit conversion, then titrate based on fasting glucose monitoring over the subsequent 3–7 days.
Conversion Rationale and Evidence
The American Diabetes Association recommends a 1:1 unit conversion when switching between long-acting basal insulin analogs (degludec, glargine U-100, detemir), meaning 23 units of degludec converts directly to 23 units of glargine U-100 as the starting dose 1.
Real-world evidence demonstrates that patients transitioning from glargine U-100 to degludec maintain similar basal insulin requirements with no significant dose changes at follow-up (median dose difference p=0.56), supporting bidirectional 1:1 conversion 2.
Head-to-head pharmacodynamic studies show that clinically titrated doses of glargine U-300 are approximately 30% higher than degludec U-100 (0.34 vs 0.26 units/kg/day), but this applies specifically to glargine U-300, not the standard U-100 formulation 3.
Critical Monitoring and Titration Protocol
Check fasting glucose daily for the first week after conversion to identify any patterns of hyper- or hypoglycemia that require dose adjustment 1, 4.
If fasting glucose is 140–179 mg/dL, increase glargine by 2 units every 3 days until reaching the target range of 80–130 mg/dL 1, 4.
If fasting glucose is ≥180 mg/dL, increase glargine by 4 units every 3 days to achieve more rapid glycemic control 1, 4.
If any glucose reading falls <70 mg/dL, immediately reduce the glargine dose by 10–20% (approximately 2–5 units) before the next administration 1, 4.
Pharmacologic Differences Requiring Vigilance
Degludec has an ultra-long half-life of approximately 25 hours compared to glargine's 12–18 hours, meaning degludec provides more stable, peak-less coverage over 42+ hours while glargine requires more consistent daily timing 5, 6.
Nocturnal hypoglycemia rates are 18–25% lower with degludec compared to glargine in clinical trials, so patients converting from degludec to glargine may experience slightly increased overnight hypoglycemia risk during the first 1–2 weeks 5, 6, 7.
Glycemic variability (measured by coefficient of variation and standard deviation of fasting glucose) is lower with degludec, so expect potentially wider day-to-day fasting glucose fluctuations after switching to glargine 8, 7.
When degludec is replaced by glargine in type 1 diabetes, a 10–25% dose reduction may be needed to avoid hypoglycemia due to differences in pharmacodynamic profiles, though this is less pronounced in type 2 diabetes 8.
Special Considerations by Formulation
If converting to glargine U-300 (Toujeo) instead of U-100 (Lantus), initiate at approximately 30 units (roughly 30% higher than the degludec dose) based on pharmacokinetic equivalence data showing glargine U-300 requires higher unit doses to achieve similar glucose control 3.
Glargine U-100 and U-300 are not interchangeable unit-for-unit; U-300 consistently requires 10–20% higher doses than U-100 to achieve equivalent glycemic control 3.
Administration Timing Flexibility
Degludec can be administered at any time of day with flexibility in timing (±8 hours), while glargine should be given at the same time daily (typically bedtime or morning) to maintain consistent 24-hour coverage 9, 5.
After conversion to glargine, establish a fixed daily injection time (e.g., 8 PM or 8 AM) and maintain it consistently to optimize basal insulin action 1, 4.
Expected Clinical Outcomes
Both insulins achieve similar HbA1c reductions (approximately 1.0–1.2% from baseline) when titrated to target fasting glucose, confirming therapeutic equivalence at appropriate doses 5, 6, 10.
Overall confirmed hypoglycemia rates are comparable between degludec and glargine (11.1 vs 13.6 episodes per patient-year), though nocturnal episodes favor degludec 6, 10.
Fasting plasma glucose reductions are slightly greater with degludec (mean difference -0.37 mmol/L), so anticipate potentially 5–10 mg/dL higher fasting glucose initially after switching to glargine 10.
Common Pitfalls to Avoid
Do not delay dose adjustments if fasting glucose consistently exceeds 180 mg/dL; prolonged hyperglycemia increases complication risk and the 1:1 conversion may be insufficient for some patients 1, 4.
Do not assume the conversion dose is final; approximately 20–30% of patients require dose adjustments within the first month after switching basal insulins 2.
Avoid converting to glargine U-300 using a 1:1 ratio; this formulation requires approximately 10–20% higher unit doses than degludec to achieve equivalent control 3.
Do not discontinue glucose monitoring after the first week; continue daily fasting checks for at least 2–3 weeks to ensure stable glycemic patterns 1, 4.