How should I adjust the insulin regimen for an adult with diabetes mellitus who is on basal NPH (Neutral Protamine Hagedorn) insulin 30 U at 8 AM and uses a carbohydrate‑to‑insulin ratio of 1 U per 8 g carbohydrate, now receiving high‑dose prednisone 60 mg daily, with capillary glucose readings of 263 mg/dL at 5 PM, 251 mg/dL at 8 PM, 351 mg/dL at 10 PM, and 421 mg/dL at 1 AM?

Immediate Insulin Regimen Adjustment for Steroid-Induced Hyperglycemia

Your current NPH 30 units at 8 AM is grossly insufficient for prednisone 60 mg daily—you need to increase the morning NPH dose to approximately 48-54 units immediately and add correctional rapid-acting insulin every 4 hours to address the escalating hyperglycemia pattern. 1, 2

Understanding the Problem

Your glucose trajectory (263→251→351→421 mg/dL from 5 PM to 1 AM) demonstrates the classic afternoon-to-midnight hyperglycemic surge caused by prednisone's pharmacodynamic profile, which peaks 4-6 hours after morning administration and maintains hyperglycemic effects throughout the day. 1, 2

• High-dose glucocorticoids (60 mg prednisone) typically require 40-60% or more additional insulin beyond baseline requirements. 1
• Your current 30-unit NPH dose represents only 0.4-0.5 units/kg (assuming 60-75 kg body weight), which is inadequate for steroid-induced insulin resistance that often demands 1.0-1.5 units/kg/day total. 2

Specific Dose Adjustments Required

Morning NPH Insulin

• Increase NPH from 30 units to 48-54 units at 8 AM (60-80% increase) to match the steroid's peak hyperglycemic effect. 1, 2
• This dose should be administered concomitantly with the prednisone to align NPH's 4-6 hour peak action with the steroid's metabolic impact. 1

Correctional Insulin Protocol

• Add rapid-acting insulin (aspart/lispro) every 4 hours using the following correction scale for glucose >150 mg/dL: 1, 2
  • 150-200 mg/dL: 2 units
  • 201-250 mg/dL: 4 units
  • 251-300 mg/dL: 6 units
  • 301-350 mg/dL: 8 units

  • 350 mg/dL: 10 units and notify provider 2, 3

Carbohydrate Ratio Adjustment

• Tighten your carb ratio from 1:8 to 1:5 (60% increase in prandial insulin) to cover meals adequately during steroid therapy. 1, 2
• This means 1 unit of rapid-acting insulin for every 5 grams of carbohydrate consumed. 2

Monitoring and Titration Protocol

• Check blood glucose every 2-4 hours for the first 48 hours after making these adjustments to identify patterns. 1, 2
• Target glucose range: 140-180 mg/dL during the day, with fasting <130 mg/dL. 1, 2
• If fasting glucose remains >130 mg/dL after 3 days, increase morning NPH by 4 units every 3 days until target achieved. 2, 3

Critical Considerations for NPH Timing

• Do not split NPH to twice daily initially—the single morning dose is specifically designed to match prednisone's pharmacokinetic profile when both are given in the morning. 1, 2
• Only consider splitting NPH (2/3 morning, 1/3 evening) if the "midday-to-midnight" hyperglycemia pattern persists despite adequate morning dosing. 2, 4

Common Pitfalls to Avoid

• Never use the same NPH dose for steroid-induced hyperglycemia as for routine diabetes management—this is the primary error in your current regimen. 1, 2
• Do not wait for gradual titration when glucose exceeds 350 mg/dL—aggressive upfront dosing is required for high-dose steroids. 1, 2
• Avoid premixed insulins (70/30) as they lack the flexibility needed for rapid dose adjustments during steroid therapy. 2

Hypoglycemia Prevention

• If any glucose reading falls <70 mg/dL, immediately reduce the corresponding insulin dose by 10-20% without waiting. 1, 2, 3
• Hypoglycemia risk peaks between midnight and 6 AM, so monitor fasting glucose closely as you uptitrate. 1

When Prednisone is Tapered or Discontinued

• Reduce NPH by 20-30% immediately when prednisone dose is decreased, as insulin requirements may drop by 50-70% within 24-48 hours of steroid discontinuation. 2
• Failure to reduce insulin proactively during steroid taper is a major cause of severe hypoglycemia. 2