What basal insulin and fixed bolus dosing strategy should be used for an adult with insulin‑treated diabetes who is currently on 46 units of NPH basal insulin and a 1 unit per 5 g carbohydrate ratio, but wants to discontinue NPH and take approximately 15 units of rapid‑acting insulin with each meal?

Transition from NPH to Fixed-Dose Rapid-Acting Insulin with Basal Coverage

For a patient on prednisone 60 mg requiring 46 units NPH and approximately 15 units rapid-acting insulin per meal, discontinue the NPH and initiate insulin glargine 23 units once daily (50% of total daily dose as basal) plus insulin aspart or lispro 15 units fixed dose with each of three meals.

Rationale for the Conversion

Your patient's current total daily insulin requirement is approximately 91 units (46 units NPH + 45 units prandial across three meals) 1. The steroid-induced hyperglycemia from prednisone 60 mg necessitates this high insulin demand, as high-dose glucocorticoids typically require 40-60% more insulin than standard dosing 1, 2.

Why Discontinue NPH in This Context

• NPH is specifically designed for steroid-induced hyperglycemia when given as a single morning dose to match the 4-8 hour peak of prednisone 3, 1
• Your patient wants fixed meal doses rather than the NPH approach, which is a reasonable preference that can be accommodated with a basal-bolus strategy 3
• NPH's intermediate-acting profile with a 4-5 hour peak makes it less ideal for providing smooth 24-hour basal coverage compared to long-acting analogs 4, 5

Specific Insulin Regimen

Basal Insulin Component

• Start insulin glargine 23 units once daily (approximately 50% of the 46-unit NPH dose, representing half of total daily insulin) 6
• Administer glargine at the same time each day—either morning or bedtime, with no clinically significant difference between timing 5
• This provides the peakless, 24-hour basal coverage that NPH cannot deliver 4, 5

Prandial (Fixed Bolus) Component

• Insulin aspart or lispro 15 units with each of three meals (breakfast, lunch, dinner) 1, 7
• Inject immediately before or at the start of the meal to match the rapid onset of these analogs 7, 8
• This fixed-dose approach eliminates carbohydrate counting while providing consistent mealtime coverage 3

Total Daily Dose Verification

• New regimen total: 68 units/day (23 basal + 45 prandial)
• This represents a 25% reduction from the current 91 units, which is appropriate because:
  • NPH has significant overlap with prandial periods, creating "double coverage" 4, 5
  • The conversion accounts for more efficient basal-bolus separation 6, 5

Monitoring and Titration Strategy

Initial 48-Hour Intensive Monitoring

• Check blood glucose every 4 hours (before meals, bedtime, and 3 AM) to identify patterns 3, 1
• Target fasting glucose <130 mg/dL and daytime glucose 140-180 mg/dL 3, 1

Basal Insulin Adjustment

• If fasting glucose remains >130 mg/dL for 3 consecutive days, increase glargine by 2 units every 3 days until target achieved 3, 1
• If fasting glucose <70 mg/dL occurs, immediately reduce glargine by 10-20% (2-5 units) 1, 2

Prandial Insulin Adjustment

• If 2-hour post-meal glucose consistently >180 mg/dL, increase that meal's insulin by 2 units 1
• If pre-meal or post-meal glucose <70 mg/dL, reduce that meal's insulin by 2-3 units (10-20%) 1, 2

Critical Considerations for Steroid Therapy

Prednisone Taper Protocol

• When prednisone is reduced, immediately decrease insulin doses proportionally 1, 2
• For each 20 mg reduction in prednisone, reduce:
  • Glargine by 20-30% (approximately 5-7 units) 1
  • Each meal dose by 20-30% (approximately 3-5 units per meal) 1
• Hypoglycemia risk peaks 24-48 hours after steroid reduction—monitor closely 1, 2

Steroid Discontinuation

• Upon complete prednisone cessation, expect insulin needs to drop by 50-70% 1
• Anticipate a final regimen of approximately:
  • Glargine 10-12 units daily 1
  • Meal doses 5-7 units each 1

Common Pitfalls to Avoid

• Do not use premixed insulin (70/30,75/25) in this scenario—it offers no flexibility for independent basal/prandial adjustments and carries high hypoglycemia risk 1
• Do not maintain the full 46-unit basal dose when converting to glargine—this will cause severe hypoglycemia because glargine provides true 24-hour coverage without gaps 6, 5
• Do not delay dose reductions during steroid taper—proactive reduction prevents dangerous hypoglycemia 1, 2
• Avoid the 1:5 carb ratio mindset with fixed dosing—the patient specifically wants meal-independent dosing, which this regimen provides 3

Why This Approach Optimizes Outcomes

• Reduced hypoglycemia risk compared to NPH due to glargine's peakless profile 5, 8
• Improved treatment satisfaction and adherence with simpler once-daily basal dosing 8
• Flexibility for steroid taper with independent basal and prandial adjustment 1, 2
• Maintains glycemic control equivalent to or better than NPH-based regimens while honoring patient preference 6, 5