NPH Insulin and Carbohydrate Ratio Adjustment for Prednisone Increase
Increase NPH insulin by approximately 40-50% (from 16 units to 24 units in the morning) and tighten the carbohydrate ratio to 1:10 for all meals when increasing prednisone from 20mg to 30mg. 1
NPH Dose Adjustment
The morning NPH dose should be increased to 24 units (a 50% increase from baseline) to match the increased hyperglycemic effect of the higher prednisone dose. 1, 2
- Prednisone causes peak hyperglycemia 4-6 hours after morning administration, making NPH insulin the optimal choice due to its intermediate-acting profile that peaks at the same time. 2, 1
- For high-dose glucocorticoids, insulin requirements typically increase by 40-60% above standard dosing. 1, 3
- Research demonstrates that patients with type 1 diabetes on prednisone require insulin dose increases of approximately 70% to maintain normoglycemia, though this patient's 50% increase is appropriate given they're already on insulin. 4
Carbohydrate Ratio Adjustment
Tighten all carbohydrate ratios to 1:10 (1 unit per 10g carbohydrate) for breakfast, lunch, and dinner. 1, 2
- The current breakfast ratio of 1:15 is too lenient for the increased steroid dose and should be tightened to 1:10. 1
- Maintaining 1:10 for all meals provides consistency and addresses the afternoon/evening hyperglycemia that characteristically occurs with prednisone. 2, 1
- Prednisone causes disproportionate hyperglycemia during the day with blood glucose often normalizing overnight, justifying uniform tightening of daytime ratios. 2, 1
Correction Scale Adjustment
Implement a correction scale of 1 unit of rapid-acting insulin for every 40-50 mg/dL above target (150 mg/dL), with more aggressive correction in the afternoon and evening. 1
- The hyperglycemic effect of prednisone peaks in the afternoon and evening, requiring more aggressive correctional insulin during these times. 2, 1
Monitoring Protocol
Monitor blood glucose every 2-4 hours initially, with special attention to afternoon and evening values when steroid effect peaks. 1, 3
- Target blood glucose range should be 80-180 mg/dL during steroid therapy. 2, 1
- Adjust insulin doses daily based on glucose patterns, as steroid-induced hyperglycemia can be highly variable. 2, 3
Critical Pitfalls to Avoid
Do not rely solely on increasing long-acting basal insulin without adding or increasing NPH insulin. 1, 3
- Long-acting insulin alone will lead to inadequate coverage of daytime hyperglycemia and potential nocturnal hypoglycemia. 1, 5
- A randomized controlled trial demonstrated that NPH-based regimens are equally effective and safe as glargine-based regimens for prednisolone-induced hyperglycemia, with the advantage of better matching the steroid's pharmacokinetic profile. 5
Be prepared to rapidly reduce insulin doses if prednisone is tapered or discontinued. 1, 3
- Insulin requirements typically decrease rapidly after steroid discontinuation, requiring prompt dose adjustments to avoid hypoglycemia. 1, 3
- When tapering steroids, reduce NPH insulin by 10-20% to prevent hypoglycemia. 1
Timing Considerations
Administer the 24 units of NPH insulin in the morning at the same time as the prednisone dose. 1, 2