Insulin Adjustment for Prednisone-Induced Hyperglycemia
Direct Answer
For patients on prednisone, increase your regular insulin doses by 40-60% or more above your baseline requirements, with the majority of this increase applied to daytime (prandial and correctional) doses rather than overnight basal insulin. 1, 2
Understanding the Hyperglycemic Pattern
Prednisone causes a distinct diurnal pattern of hyperglycemia that is critical to understand:
- Hyperglycemia peaks 4-6 hours after morning prednisone administration and persists throughout the day, particularly affecting afternoon and evening blood glucose levels. 1, 2
- Blood glucose often normalizes overnight even without treatment, which is why increasing long-acting basal insulin alone can lead to nocturnal hypoglycemia. 2, 3
- The hyperglycemic effect is dose-dependent—higher prednisone doses require proportionally larger insulin increases. 1, 2
Specific Insulin Adjustment Strategy
For Regular Insulin (Humulin R):
Prandial Coverage:
- Start with 1 unit of regular insulin per 10-15 grams of carbohydrate in meals. 1
- Increase this ratio by 40-60% for lunch and dinner doses (the meals most affected by prednisone). 1, 2
- Morning breakfast coverage may require less aggressive increases since prednisone hasn't peaked yet. 2
Correctional (Sliding Scale) Coverage:
- Administer regular insulin every 6 hours for hyperglycemia. 1
- Use a more aggressive correction scale during afternoon and evening hours: start with 1 unit for every 40-50 mg/dL above target (150 mg/dL), but you may need to double this during peak steroid effect times. 4
- Target blood glucose range should be 100-180 mg/dL. 1, 2
Adding NPH Insulin (Strongly Recommended):
NPH insulin is specifically designed to match prednisone's pharmacokinetics and should be added to your regimen:
- Start NPH at 0.3-0.5 units/kg/day given in the morning (at the same time as prednisone or within a few hours). 2, 4
- NPH peaks 4-6 hours after administration, perfectly matching prednisone's peak hyperglycemic effect. 1, 2
- This is given in addition to your regular insulin for meals and corrections, not as a replacement. 1, 4
Monitoring Protocol
- Check blood glucose at least 4 times daily: fasting and 2 hours after each meal. 2
- Pay particular attention to afternoon readings (2-6 PM), as this captures the peak steroid effect. 2, 4
- Do not rely on fasting glucose alone—this will miss the peak hyperglycemic effect and lead to undertreatment. 2, 4
Critical Adjustments During Steroid Taper
When prednisone dose is reduced, immediately decrease insulin doses proportionally (typically 10-20% reduction for each steroid dose reduction) to prevent hypoglycemia. 2, 4
- Insulin sensitivity improves within days of steroid dose reduction. 4
- Failure to reduce insulin promptly is a common cause of severe hypoglycemia. 2, 4
Common Pitfalls to Avoid
- Using only sliding-scale regular insulin without scheduled doses leads to poor glycemic control—you need both scheduled prandial insulin AND correctional doses. 1, 2
- Increasing only basal (long-acting) insulin causes nocturnal hypoglycemia while leaving daytime hyperglycemia undertreated. 2, 3
- Waiting for fasting hyperglycemia before treating results in delayed intervention, as fasting glucose may remain normal despite severe daytime hyperglycemia. 2, 4
- Relying solely on oral diabetes medications for high-dose steroid therapy is inadequate—insulin is required. 2