Adjusting NPH Insulin During Prednisolone Taper
Reduce the NPH insulin dose from 30 units to 24 units (a 20% reduction) when tapering prednisolone from 60 mg to 50 mg. 1
Rationale for the 20% Dose Reduction
The American Diabetes Association recommends reducing NPH insulin by 10-20% when tapering steroids to prevent hypoglycemia, and a 20% reduction is appropriate for this magnitude of steroid taper (approximately 17% reduction in prednisolone dose). 1
Prednisolone causes hyperglycemia predominantly between midday and midnight, and as the steroid dose decreases, the hyperglycemic effect diminishes proportionally, requiring less insulin coverage. 2
For patients on high-dose glucocorticoids, insulin requirements are commonly 40-60% higher than standard dosing, so as prednisolone decreases, these elevated requirements normalize accordingly. 1
Monitoring Protocol After Dose Adjustment
Check blood glucose every 2-4 hours for the first 24-48 hours after making this adjustment to identify patterns of hyper- or hypoglycemia and ensure the new dose is appropriate. 1, 3
Target blood glucose range of 80-180 mg/dL for hospitalized patients, or fasting glucose <130 mg/dL and daytime glucose 140-180 mg/dL for outpatients. 1
If hypoglycemia occurs (glucose <70 mg/dL), immediately reduce the NPH dose by an additional 10-20% (to approximately 19-22 units) without waiting. 1, 4
Further Adjustments as Prednisolone Continues to Taper
Each time prednisolone is reduced by approximately 10 mg, consider reducing NPH by an additional 10-20% to maintain proportional coverage. 1
If fasting glucose remains elevated above 130 mg/dL after 3 days on the new dose, increase NPH by 2 units every 3 days until target glucose is achieved without hypoglycemia. 1, 3
Watch for the "midday to midnight" hyperglycemia pattern characteristic of prednisolone—if this pattern diminishes or disappears, it confirms the steroid effect is waning and further NPH reduction may be needed. 1, 4
Special Considerations for Complete Steroid Discontinuation
When prednisolone is completely discontinued, insulin needs may drop by 50-70% within 24-48 hours, requiring aggressive NPH dose reduction or potential discontinuation depending on the patient's baseline diabetes status. 1
For patients without pre-existing diabetes, NPH can often be discontinued entirely once prednisolone is stopped, though glucose monitoring should continue for 48-72 hours. 1
For patients with pre-existing diabetes, return to their baseline insulin regimen (prior to steroid initiation) once prednisolone is fully tapered. 1
Common Pitfalls to Avoid
Do not wait for hypoglycemia to occur before reducing the dose—proactive reduction based on steroid taper is safer and prevents dangerous glucose excursions. 1, 4
Do not maintain the same NPH dose throughout the entire steroid taper, as this creates unacceptable hypoglycemia risk as the hyperglycemic effect of prednisolone diminishes. 1
If the patient develops hypoglycemia during the taper, further lower the NPH dose by an additional 10-20% beyond the planned reduction. 1