Converting 20 Units BID of 70/30 Insulin to Lantus
Start Lantus at 32 units once daily (80% of the total daily 70/30 dose of 40 units), administered at the same time each day, and closely monitor blood glucose for the first several weeks with dose adjustments as needed. 1
Conversion Algorithm
The FDA-approved Lantus prescribing information provides explicit guidance for this conversion 1:
- Calculate total daily 70/30 dose: 20 units × 2 = 40 units/day
- Apply 80% reduction: 40 units × 0.80 = 32 units once daily
- Timing: Administer at bedtime or any consistent time daily
This 20% dose reduction is specifically recommended when converting from twice-daily NPH-containing insulins (which includes 70/30 premixed insulin, as the "70" component is NPH) to once-daily Lantus to lower the likelihood of hypoglycemia 1.
Critical Implementation Points
Close glucose monitoring is mandatory during and after this conversion 1. The 2025 ADA Standards of Care emphasize that any insulin regimen change requires medical supervision with appropriate glucose monitoring 2.
What You're Losing in the Conversion
The 70/30 insulin provided:
- Basal coverage from the NPH component (70%)
- Prandial coverage from the regular insulin component (30%)
You must address the loss of prandial insulin coverage. Lantus provides only basal insulin with no prandial component 1. The patient will likely need:
- Addition of mealtime rapid-acting insulin (start with 4 units at the largest meal or 10% of basal dose per meal) 2
- OR continuation/optimization of oral antidiabetic agents if this is type 2 diabetes
- OR consideration of GLP-1 receptor agonist therapy 2
Titration After Conversion
Once converted to Lantus 32 units daily:
- Set fasting plasma glucose goal (typically <100 mg/dL or <5.5 mmol/L)
- Titrate by 2 units every 3 days to reach FPG goal without hypoglycemia 2
- For hypoglycemia: Determine cause; if no clear reason, reduce dose by 10-20% 2
Common Pitfalls to Avoid
Do NOT convert unit-for-unit (40 units to 40 units) - this increases hypoglycemia risk significantly, particularly since you're eliminating one of the twice-daily NPH doses 1, 3
Do NOT mix Lantus with other insulins - it must be administered separately due to its acidic pH 4, 1
Do NOT forget about prandial coverage - patients often experience postprandial hyperglycemia after losing the regular insulin component of 70/30 2
Watch for overbasalization - if you keep increasing Lantus to control postprandial glucose, you'll cause fasting hypoglycemia. Clinical signals include bedtime-to-morning glucose differential ≥50 mg/dL, hypoglycemia, or high glucose variability 2
Supporting Evidence
Research confirms that twice-daily NPH (the basal component of 70/30) requires an initial 20% dose reduction when converting to once-daily glargine 3, 5. The Lantus FDA label explicitly states this conversion principle 1. While some older literature suggested unit-for-unit conversion from once-daily NPH, the twice-daily regimen requires dose reduction 3, 6.
The 2025 ADA guidelines emphasize individualized titration based on glucose monitoring rather than fixed protocols, but provide the 80% conversion as a safe starting point 2.