A patient taking prednisone 60 mg and NPH insulin 20 units at 8 am with a carbohydrate‑to‑insulin ratio of 1 unit per 10 g has blood glucose 201 mg/dL at noon and 325 mg/dL at 4 pm; how should the NPH dose and carb ratio be adjusted?

NPH Insulin and Carbohydrate Ratio Adjustment for Steroid-Induced Hyperglycemia

Immediate NPH Dose Increase

Increase the morning NPH insulin from 20 units to 32 units (a 60% increase) to address the severe afternoon hyperglycemia caused by prednisone 60 mg. 1, 2

• The blood glucose rise from 201 mg/dL at noon to 325 mg/dL at 4 PM demonstrates inadequate NPH coverage during the peak steroid effect window 1, 2
• High-dose glucocorticoids (60 mg prednisone) typically require 40–60% increases in insulin doses above baseline 1, 3
• NPH insulin peaks 4–6 hours after administration, which aligns perfectly with the 8 AM dose peaking at noon–2 PM, but the current 20-unit dose is insufficient for 60 mg prednisone 1, 2
• For a patient on 60 mg prednisone, an initial NPH dose of 0.1–0.2 units/kg is recommended; assuming ~70 kg body weight, this translates to 7–14 units as a starting dose, but this patient clearly needs more given the observed hyperglycemia 1, 2

Carbohydrate Ratio Adjustment

Tighten the carbohydrate ratio from 1:10 to 1:6 (increase prandial insulin by approximately 67%) to cover the steroid-induced insulin resistance. 1, 2

• The 1:10 ratio (1 unit per 10 g carbohydrate) is a standard starting point, but high-dose steroids create severe insulin resistance that demands more aggressive prandial coverage 1, 2
• Prednisone causes disproportionate hyperglycemia during midday-to-midnight hours, requiring substantially more prandial insulin at lunch and dinner 1, 2
• A 1:6 ratio means the patient will administer approximately 1 unit of rapid-acting insulin for every 6 grams of carbohydrate consumed 1, 2
• This adjustment should be applied primarily to lunch and dinner meals, where steroid effect is maximal 1, 2

Algorithmic Titration Protocol

NPH Titration (Every 3 Days)

• If afternoon glucose (12 PM–6 PM) remains >180 mg/dL, increase morning NPH by 4 units 1, 3
• If afternoon glucose is 140–179 mg/dL, increase morning NPH by 2 units 1, 3
• Target afternoon glucose: 80–180 mg/dL 1, 2
• Stop NPH escalation if the dose exceeds 0.5 units/kg/day (~35 units for a 70-kg patient) without achieving targets; at that point, consider splitting NPH to twice daily (2/3 morning, 1/3 evening) 1, 3

Prandial Insulin Titration (Every 3 Days)

• Check 2-hour post-meal glucose after lunch and dinner 1, 3
• If post-meal glucose is >180 mg/dL, tighten the carb ratio further (e.g., from 1:6 to 1:5) 1, 2
• If post-meal glucose is <100 mg/dL, loosen the ratio (e.g., from 1:6 to 1:8) 1, 3

Correction Scale Adjustment

Increase the correction factor from 1 unit per 50 mg/dL to 1 unit per 30–40 mg/dL above target (150 mg/dL) for afternoon/evening corrections. 1, 2

• Steroid-induced insulin resistance peaks in the afternoon, requiring more aggressive correction dosing during this window 1, 2
• For a glucose of 325 mg/dL at 4 PM, the correction dose would be: (325 – 150) ÷ 35 = 5 units of rapid-acting insulin 1, 2
• Morning correction doses can remain at the standard 1 unit per 50 mg/dL, as steroid effect is minimal overnight 1, 2

Monitoring Requirements

• Check blood glucose every 2–4 hours initially (fasting, pre-lunch, 2 PM, 4 PM, pre-dinner, bedtime) to capture the steroid effect curve 1, 2
• Pay special attention to afternoon and evening values (12 PM–midnight), when prednisone causes maximal hyperglycemia 1, 2
• Fasting glucose is often normal or near-normal despite severe daytime hyperglycemia, so do not use fasting glucose alone to guide NPH dosing 1, 2

Critical Pitfalls to Avoid

• Do not rely solely on long-acting basal insulin (e.g., glargine) without adding NPH, as basal insulin provides flat 24-hour coverage and cannot match the midday-to-midnight hyperglycemia pattern caused by prednisone 1, 2
• Do not use fasting glucose to titrate NPH, as prednisone's effect wanes overnight; instead, use afternoon glucose (12 PM–6 PM) to guide NPH adjustments 1, 2
• Do not delay dose increases—the 125 mg/dL rise from noon to 4 PM indicates profound insulin deficiency during the steroid peak 1, 2
• Prepare for rapid dose reductions when prednisone is tapered or discontinued; insulin requirements typically drop by 50–70% within 24–48 hours of steroid cessation, creating high hypoglycemia risk 1, 3

Expected Outcomes

• With the increased NPH (32 units) and tightened carb ratio (1:6), afternoon glucose should fall to 140–180 mg/dL within 3–5 days 1, 2
• If glucose remains >180 mg/dL after 3 days, increase NPH by another 4 units and consider further tightening the carb ratio to 1:5 1, 3
• Hypoglycemia risk is low during the steroid course but becomes very high once prednisone is tapered; at that point, reduce NPH by 20–30% immediately and loosen the carb ratio back toward 1:10 1, 3