Dose Conversion from Tresiba to Lantus
When converting from 80 units of Tresiba (insulin degludec) to Lantus (insulin glargine), start with 80 units of Lantus administered once daily, as the two basal insulins are dosed on a unit-to-unit basis for conversion purposes.
Conversion Rationale
- The American Diabetes Association guidelines for basal insulin dosing do not specify different conversion ratios between insulin degludec and insulin glargine, as both are long-acting basal insulins designed to provide 24-hour coverage 1
- A 1:1 unit conversion (80 units Tresiba → 80 units Lantus) is the standard clinical approach, though close monitoring and dose adjustment will be necessary due to pharmacodynamic differences between these insulins 1
Critical Pharmacologic Differences to Consider
While the initial dose conversion is 1:1, you must understand that these insulins have different pharmacologic profiles:
- Insulin degludec has an ultra-long duration of action (>42 hours) with lower day-to-day variability compared to insulin glargine's approximately 24-hour duration 2, 3
- Studies demonstrate that degludec provides 25% lower nocturnal hypoglycemia rates compared to glargine in type 1 diabetes, and significantly reduced nocturnal time below range in type 2 diabetes 2, 4
- Meta-analyses show degludec is associated with 17-36% lower nocturnal hypoglycemia rates across different diabetes populations compared to glargine 5
Post-Conversion Monitoring and Titration Protocol
After converting to 80 units of Lantus, implement the following monitoring strategy:
- Monitor fasting blood glucose daily for the first 2-3 weeks to assess adequacy of basal coverage, as the shorter duration of glargine may reveal gaps in 24-hour coverage that were masked by degludec's ultra-long action 1
- Titrate Lantus by 2-4 units every 3 days based on fasting glucose patterns: increase by 2 units if fasting glucose is 140-179 mg/dL, or by 4 units if ≥180 mg/dL 1
- Target fasting plasma glucose of 80-130 mg/dL 1
- If hypoglycemia occurs without clear cause, reduce the dose by 10-20% immediately 1
Common Pitfalls to Avoid
- Do not assume equivalent 24-hour coverage: Some patients may require twice-daily Lantus dosing if once-daily administration fails to provide adequate 24-hour coverage, particularly in type 1 diabetes patients who were stable on once-daily degludec 1
- Watch for increased nocturnal hypoglycemia: The patient may experience more nocturnal hypoglycemic episodes with glargine compared to their previous degludec regimen, requiring dose reduction 2, 4, 5
- Monitor for end-of-dose waning: If morning hyperglycemia develops despite adequate evening glucose control, this suggests glargine is not providing full 24-hour coverage and may require splitting to twice-daily dosing 1
- Avoid overbasalization: If the Lantus dose exceeds 0.5 units/kg/day (approximately 40 units for an 80 kg patient) and glucose control remains inadequate, add prandial insulin rather than continuing to escalate basal insulin alone 1
Special Considerations
- Real-world data suggests that patients may require lower total daily doses with degludec compared to glargine while achieving similar glycemic control, so the reverse conversion may necessitate slightly higher Lantus doses in some patients 6
- Continue metformin unless contraindicated when making this basal insulin switch 1
- Reassess adequacy of insulin dose at every clinical visit, looking specifically for signs of overbasalization or inadequate coverage 1