A patient on insulin degludec 8 units, NPH 28 units, and a carbohydrate‑to‑insulin ratio of 1 unit per 6 g has blood glucose values of 134 mg/dL at 8 am, 177 mg/dL at noon, 198 mg/dL at 5 pm, 270 mg/dL at 9 pm, and 100 mg/dL at 2 am. If the degludec dose will be reduced to 6 units today, what should the NPH dose be and what carbohydrate‑to‑insulin ratio should be used?

Adjust NPH to 22 Units and Tighten Carbohydrate Ratio to 1:5

With dexamethasone reduced from 8 mg to 6 mg (a 25% reduction), you should decrease the NPH dose from 28 units to approximately 22 units (a 20% reduction) and adjust the carbohydrate-to-insulin ratio from 1:6 to approximately 1:5 to maintain adequate glycemic control during the steroid taper. 1

Understanding the Steroid-Insulin Relationship

• Dexamethasone causes hyperglycemia predominantly between midday and midnight, with peak effect occurring 4–8 hours after morning administration 1, 2
• High-dose glucocorticoids typically require 40–60% more insulin than standard dosing due to severe insulin resistance 1, 2
• Morning administration of NPH insulin is specifically recommended for steroid-induced hyperglycemia because its 4–6 hour peak aligns with the steroid's metabolic effect 1, 2

Calculating the New NPH Dose

• When tapering steroids, the American Diabetes Association recommends reducing insulin doses proportionally—typically a 10–20% reduction for each significant decrease in steroid dose 1, 2
• For a 25% reduction in dexamethasone (from 8 mg to 6 mg), a 20% reduction in NPH is appropriate: 28 units × 0.80 = 22.4 units, rounded to 22 units 1
• If hypoglycemia occurs during the taper, further lower the NPH dose by an additional 10–20% (approximately 2–4 units) 1, 2

Adjusting the Carbohydrate Ratio

• The carbohydrate ratio should be adjusted from 1:6 to approximately 1:5, representing a 20% tightening in prandial insulin requirements 1, 2
• For patients on high-dose steroids, a more aggressive carbohydrate ratio is needed, with a starting point of 1 unit of rapid-acting insulin for every 5–8 grams of carbohydrate 2
• This ratio may need further adjustment based on 2-hour postprandial glucose monitoring results 1, 2

Monitoring and Further Adjustments

• Check blood glucose every 2–4 hours for the first 24–48 hours after making these adjustments to identify patterns of hyper- or hypoglycemia 1, 2
• Target fasting glucose <130 mg/dL and daytime glucose 140–180 mg/dL 1, 2
• If fasting glucose remains elevated above 130 mg/dL after 3 days, increase NPH by 2 units every 3 days until target is achieved 1
• If you develop hypoglycemia (glucose <70 mg/dL) at any point, immediately reduce the corresponding insulin dose by 10–20% without waiting 1, 2

Anticipating Further Steroid Taper

• As dexamethasone is further reduced or discontinued, insulin needs may drop by 50–70% within 24–48 hours 1
• For each subsequent 2 mg decrease in dexamethasone, plan to reduce NPH by approximately 20–30% (4–6 units) 1
• Upon complete dexamethasone cessation, you may require only 10–12 units of basal insulin daily with a carbohydrate ratio returning toward 1:8 to 1:10 1

Special Considerations for Your Blood Glucose Pattern

• Your 2 AM glucose of 100 mg/dL indicates adequate overnight basal coverage, but the progressive rise from 134 mg/dL (8 AM) to 270 mg/dL (9 PM) demonstrates the characteristic "midday to midnight" hyperglycemia pattern of prednisone/dexamethasone 1
• The 9 PM peak of 270 mg/dL followed by normalization to 100 mg/dL by 2 AM confirms that NPH is appropriately timed but was previously under-dosed relative to the 8 mg dexamethasone 1
• With the reduction to 6 mg dexamethasone, the 22-unit NPH dose should prevent the evening hyperglycemic spike while avoiding nocturnal hypoglycemia 1

Common Pitfalls to Avoid

• Do not delay dose reductions when tapering steroids—failure to reduce insulin proportionally is the most common cause of hypoglycemia during steroid tapers 1, 2
• Do not split the NPH into twice-daily doses initially; a single morning injection is specifically designed to match the pharmacokinetic profile of morning-administered dexamethasone 1
• Do not maintain the full 28-unit NPH dose with reduced dexamethasone, as this creates significant hypoglycemia risk, particularly overnight when steroid effect wanes 1, 2
• If daytime hyperglycemia persists despite dose adjustments, consider splitting NPH to twice daily (2/3 morning, 1/3 evening) rather than further increasing the morning dose 1