Switching from Novolog to NPH at Discharge: Not Recommended
Do not replace rapid-acting insulin (Novolog) with NPH alone at discharge—this substitution eliminates essential mealtime coverage and will result in dangerous post-prandial hyperglycemia. 1
Why NPH Alone Is Inadequate
- NPH is an intermediate-acting basal insulin designed to suppress hepatic glucose production between meals and overnight, not to cover carbohydrate intake at meals 1, 2.
- Novolog is a rapid-acting prandial insulin that blunts post-meal glucose excursions; removing it leaves the patient with no mealtime insulin coverage 1.
- A patient requiring 10 units of Novolog per meal (carb ratio 1:15) has substantial prandial insulin needs that NPH cannot address 1.
- NPH peaks 4–6 hours after injection, creating a mismatch with meal timing and raising the risk of both hypoglycemia (during the peak) and hyperglycemia (when meals are consumed without rapid-acting coverage) 1, 3, 4.
Correct Discharge Regimen: Basal-Bolus Therapy
Basal Insulin Component
- Initiate long-acting basal insulin (glargine, detemir, or degludec) at approximately 50% of the total daily insulin dose 1.
- For a patient using 30 units/day of Novolog (10 units × 3 meals), start basal insulin at ≈15 units once daily 1.
- Alternatively, if NPH is the only available basal option, administer it twice daily (e.g., 8 units morning, 7 units bedtime) to provide more consistent 24-hour coverage 1, 4.
Prandial Insulin Component
- Continue rapid-acting insulin (Novolog or an equivalent) at 10 units before each meal to cover the carbohydrate load 1.
- Administer prandial insulin 0–15 minutes before meals for optimal post-prandial glucose control 1.
Titration Protocol
- Basal insulin: Increase by 2 units every 3 days if fasting glucose is 140–179 mg/dL; increase by 4 units every 3 days if fasting glucose ≥180 mg/dL, targeting 80–130 mg/dL 1.
- Prandial insulin: Adjust each meal dose by 1–2 units every 3 days based on 2-hour post-prandial glucose, targeting <180 mg/dL 1.
Why NPH Monotherapy Fails in This Context
- NPH does not provide flat basal coverage; its pronounced peak 4–6 hours post-injection causes nocturnal hypoglycemia when given at bedtime and mid-day hypoglycemia when given in the morning 1, 2, 3.
- NPH duration is <24 hours, requiring twice-daily dosing to maintain basal insulin levels 2, 4.
- Eliminating prandial insulin in a patient with a 1:15 carb ratio (indicating significant insulin need) will result in post-prandial glucose values routinely exceeding 250–300 mg/dL 1.
- Sliding-scale correction insulin alone is condemned by major diabetes guidelines as reactive rather than preventive, leading to dangerous glucose fluctuations 1.
If NPH Must Be Used (Resource-Limited Settings)
Twice-Daily NPH Regimen
- Administer NPH twice daily (e.g., 2/3 of total dose in the morning, 1/3 at bedtime) to approximate basal coverage 1, 4.
- Continue rapid-acting insulin (Novolog) at meals to address prandial needs 1.
NPH + Regular Insulin Alternative
- If rapid-acting analogs are unavailable, use regular insulin 30–45 minutes before meals in combination with twice-daily NPH 1.
- Regular insulin has a slower onset and longer duration than Novolog, requiring earlier administration 1.
Monitoring and Safety
- Check fasting glucose daily to guide basal insulin titration 1.
- Measure pre-meal and 2-hour post-prandial glucose to assess prandial insulin adequacy 1.
- Treat hypoglycemia (<70 mg/dL) immediately with 15 g fast-acting carbohydrate and reduce the implicated insulin dose by 10–20% 1.
- Never use rapid-acting insulin at bedtime as a sole correction dose, as this markedly raises nocturnal hypoglycemia risk 1.
Common Pitfalls to Avoid
- Do not discontinue prandial insulin when switching to NPH; this eliminates essential mealtime coverage 1.
- Do not rely solely on NPH to manage both basal and prandial needs; NPH's pharmacokinetic profile is unsuitable for meal coverage 1, 2, 3.
- Do not use sliding-scale insulin as monotherapy; correction doses must supplement a scheduled basal-bolus regimen 1.
- Avoid NPH monotherapy in type 1 diabetes, as it can precipitate diabetic ketoacidosis due to inadequate basal coverage 1.
Expected Clinical Outcomes
- Basal-bolus therapy (long-acting basal + rapid-acting prandial) enables ≈68% of patients to achieve mean glucose <140 mg/dL, versus ≈38% with inadequate regimens 1.
- Properly implemented basal-bolus regimens do not increase hypoglycemia incidence compared with suboptimal approaches 1.
- NPH alone will fail to control post-prandial hyperglycemia in a patient requiring 10 units of Novolog per meal, resulting in glucose values routinely exceeding 250 mg/dL 1.