NPH Insulin Dosing Schedule
When splitting NPH insulin, administer 2/3 of the total daily dose before breakfast and 1/3 before dinner. 1
Standard Split-Dose Regimen
The twice-daily NPH schedule is the recommended approach when intensifying from once-daily dosing:
- Split the total NPH dose with 2/3 administered before breakfast and 1/3 administered before dinner 1
- When converting from bedtime-only NPH to a split regimen, reduce the total NPH dose to 80% of the current bedtime dose, then divide according to the 2/3:1/3 ratio 1
- Add 4 units of short/rapid-acting insulin to each injection, or 10% of the reduced NPH dose, for prandial coverage 1
Initial NPH Dosing (Once-Daily)
For patients starting NPH insulin:
- Begin with bedtime administration at 10 units per day OR 0.1-0.2 units/kg per day 1
- Titrate by increasing 2 units every 3 days to reach fasting plasma glucose goal without hypoglycemia 1
- If hypoglycemia occurs without clear cause, reduce the dose by 10-20% 1
When to Convert to Twice-Daily NPH
Consider splitting to twice-daily NPH when:
- A1C remains above goal despite optimized bedtime NPH dosing 1
- Adding prandial insulin coverage is needed 1
- Daytime hyperglycemia persists despite dose adjustments 2
Special Clinical Scenarios
Steroid-Induced Hyperglycemia
- Administer NPH in the morning (not split) to match the pharmacokinetic profile of daily glucocorticoid therapy 2
- This timing aligns with the peak hyperglycemic effect of glucocorticoids, which occurs 4-6 hours after steroid administration 2
Type 1 Diabetes with Intensive Control
- Research demonstrates that splitting evening insulin by giving regular insulin at dinner and NPH at bedtime (rather than mixing both at dinner) reduces nocturnal hypoglycemia by 64% (0.10 vs 0.28 episodes/patient-day) and improves HbA1c (7.0% vs 7.5%) 3
- This split-evening approach is superior to administering both insulins together before dinner 3
Type 2 Diabetes
- Bedtime NPH administration may be preferable to morning dosing in Type 2 diabetes, resulting in better fasting glucose control (4.6 vs 8.6 mmol/L) and lower HbA1c (5.81% vs 6.23%) 4
- However, when splitting is required for intensification, use the standard 2/3 morning, 1/3 evening distribution 1
Common Pitfalls to Avoid
- Do not give equal doses morning and evening—the 2/3:1/3 ratio accounts for greater insulin sensitivity overnight and reduces nocturnal hypoglycemia risk 1
- Do not maintain the same total daily dose when converting from once to twice-daily—reduce to 80% of the bedtime dose first 1
- Avoid administering both NPH and rapid-acting insulin together at dinner in Type 1 diabetes—this increases nocturnal hypoglycemia compared to separating NPH to bedtime 3
- For patients on tube feeding requiring NPH, consider splitting into twice or three times daily to cover continuous nutritional intake 5