Twice-Daily NPH Insulin Dosing Regimen
When converting from bedtime-only NPH to a twice-daily regimen, reduce the total dose to 80% of the current bedtime NPH dose, then administer 2/3 of this reduced dose before breakfast and 1/3 before dinner. 1
Initial Dosing for Twice-Daily NPH
For patients starting NPH insulin who require twice-daily dosing:
Begin with 10 units per day or 0.1-0.2 units/kg per day as a single bedtime dose, then convert to twice-daily when glycemic targets are not met with bedtime dosing alone 1
When splitting to twice-daily, calculate 80% of the current bedtime NPH dose as the new total daily dose 1, 2
Distribute this reduced total as 2/3 before breakfast and 1/3 before dinner (not equal doses—this ratio accounts for greater overnight insulin sensitivity and reduces nocturnal hypoglycemia risk) 1, 3
Conversion Example
If a patient is on 30 units of bedtime NPH:
- New total daily dose = 24 units (80% of 30 units) 2
- Morning dose = 16 units (2/3 of 24 units) 2
- Evening dose = 8 units (1/3 of 24 units) 2
Titration Protocol
Increase the dose by 2 units every 3 days to reach fasting plasma glucose target without hypoglycemia 1, 3
Monitor fasting glucose to assess the evening NPH dose adequacy; monitor pre-dinner glucose to assess morning NPH dose adequacy 2
If hypoglycemia occurs without clear cause, reduce the corresponding dose by 10-20% 1, 4, 3
Adding Prandial Coverage
When twice-daily NPH alone is insufficient:
Add 4 units of short/rapid-acting insulin to each injection, or 10% of the reduced NPH dose, for prandial coverage 1, 3
This creates a self-mixed/split regimen where NPH and rapid-acting insulins can be adjusted separately 1
Critical Pitfalls to Avoid
Never convert unit-for-unit from once-daily to twice-daily dosing—always use the 80% reduction to prevent hypoglycemia during transition 2, 3
Never give equal morning and evening doses—the 2/3:1/3 ratio is essential for preventing nocturnal hypoglycemia 3
Never delay dose adjustments—reassess every 3 days and titrate based on glucose patterns 2
Do not give NPH at bedtime when initiating twice-daily dosing—use the before-dinner timing (1/3 dose) instead 1, 3
Special Considerations
Prescribe glucagon for emergent hypoglycemia when initiating NPH therapy, as NPH carries higher hypoglycemia risk than long-acting basal analogs 1
For patients on continuous tube feeding requiring NPH, consider splitting into twice or three times daily to cover continuous nutritional intake 3
Consider switching from NPH to a basal analog if the patient develops frequent hypoglycemia or consistently forgets evening NPH administration 1