Switching from NPH Insulin to Lantus (Insulin Glargine)
When switching from NPH insulin to Lantus, use a unit-to-unit conversion at the same total daily dose, though consider reducing the dose by 10-20% if the patient has a history of hypoglycemia or A1C <8%. 1
Conversion Strategy Based on NPH Regimen
If Patient is on Once-Daily Bedtime NPH:
- Switch to Lantus at the same total daily dose, administered once daily at bedtime or in the morning 2, 3
- Lantus can be given at any time of day that is convenient for the patient, unlike NPH which must be given at bedtime 2, 4
- The primary advantage is a 26% reduction in nocturnal hypoglycemia and 46% reduction in severe hypoglycemia compared to NPH 5
If Patient is on Twice-Daily NPH:
- Calculate the total daily NPH dose and convert unit-to-unit to once-daily Lantus 3
- For example, if a patient takes NPH 20 units in the morning and 15 units at bedtime (total 35 units), start Lantus at 35 units once daily 3
- Consider reducing the initial Lantus dose by 10-20% (to approximately 28-31 units in this example) if A1C is <8% or if there is a history of hypoglycemia 1
Timing of Administration
- Lantus provides a flat, peakless 24-hour insulin profile, allowing flexible dosing at any time of day 2, 4
- Studies show no difference in glycemic control whether Lantus is given at dinnertime or bedtime 4
- Choose a consistent time that fits the patient's schedule to improve adherence 2
Expected Outcomes and Safety Benefits
Hypoglycemia Reduction:
- Overall symptomatic hypoglycemia is reduced by 11% with Lantus compared to NPH 5
- Nocturnal hypoglycemia is reduced by 26% 5
- Severe hypoglycemia is reduced by 46% 5
- Severe nocturnal hypoglycemia is reduced by 59% 5
Glycemic Control:
- Lantus achieves equivalent or superior A1C reduction compared to NPH 5, 4, 6
- In one study, A1C decreased from 6.8-7.0% to 6.4-6.6% with Lantus versus no change with NPH 4
- Mean daily blood glucose is lower with Lantus (7.4-7.5 mmol/L) compared to NPH (8.3 mmol/L) 4
Titration After Conversion
- Start titration 3 days after the switch 3
- Increase by 2-4 units once or twice per week based on fasting plasma glucose 3
- Target fasting plasma glucose of 80-130 mg/dL (4.4-7.2 mmol/L) 3
- If hypoglycemia occurs without clear cause, reduce the dose by 10-20% 1
Special Considerations and Common Pitfalls
Avoid Mixing Insulins:
- Lantus should NOT be mixed with short-acting insulins in the same syringe, as it will coprecipitate and lose efficacy 2
- This requires separate injections if prandial insulin is needed 2
Consider Switching Indications:
- Switch from evening NPH to Lantus if the patient develops recurrent hypoglycemia 1
- Switch if the patient frequently forgets evening NPH doses and would benefit from morning dosing flexibility 1
Monitor for Overbasalization:
- Do not exceed approximately 0.5-1.0 units/kg/day without reassessing the regimen 3
- If basal insulin requirements exceed this threshold without achieving glycemic targets, consider adding prandial insulin or GLP-1 receptor agonists rather than continuing to escalate basal insulin 1, 3
Type 1 vs Type 2 Diabetes:
- In labile type 1 diabetes, Lantus may be most effective when split into two daily doses 2
- In obese, insulin-resistant type 2 diabetes patients, consider splitting the dose due to high volume requirements 2