What should the carb ratio, correction scale, and NPH insulin dose be for a 70-year-old male patient with diabetes, impaired renal function requiring dialysis, and recently initiated on prednisone, who is currently on Lantus (insulin glargine) 14 units daily?

Insulin Management for Steroid-Induced Hyperglycemia in Dialysis Patient

Direct Recommendation

Switch from Lantus to NPH insulin 20-25 units given in the morning, adjust carbohydrate ratio to 1:6, and use a correction factor of 1 unit per 25 mg/dL above 150 mg/dL. 1

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NPH Insulin Dosing

Morning NPH insulin is the preferred basal insulin for prednisone-induced hyperglycemia because its 4-6 hour peak action aligns with the hyperglycemic effect of glucocorticoids, unlike Lantus which has no peak and will under-treat daytime hyperglycemia while risking nocturnal hypoglycemia. 1, 2

Calculating the NPH Dose:

• Start with 0.3-0.4 units/kg for patients on high-dose steroids (≥40 mg prednisone). 3
• For this 75 kg patient: 0.3 × 75 = 22.5 units, round to 20-25 units NPH in the morning 1, 3
• This represents approximately 150-180% of the current basal insulin dose, which is appropriate given the 40 mg prednisone dose 2

Critical Timing:

• Administer NPH in the morning (same time as prednisone) to match the steroid's peak hyperglycemic effect occurring midday to midnight 1, 3
• Do NOT give NPH at bedtime—this will cause nocturnal hypoglycemia and miss daytime hyperglycemia 2

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Carbohydrate Ratio Adjustment

Tighten the carbohydrate ratio from 1:8 to 1:6 (1 unit per 6 grams of carbohydrate) for meal coverage. 3

Rationale:

• High-dose steroids increase insulin resistance by 40-60%, requiring more aggressive prandial insulin 1
• The current 1:8 ratio is insufficient for 40 mg prednisone 3
• Use rapid-acting insulin (aspart, lispro, or glulisine) before each meal with this ratio 2

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Correction Scale (Insulin Sensitivity Factor)

Use 1 unit per 25 mg/dL above target of 150 mg/dL (more aggressive than the previous 1:35 ISF). 3

Specific Correction Doses:

• 150-175 mg/dL: 1 unit 3
• 176-200 mg/dL: 2 units 3
• 201-225 mg/dL: 3 units 3
• 226-250 mg/dL: 4 units 3
• 251-275 mg/dL: 5 units 3
• >275 mg/dL: 6 units and notify provider 3

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Special Considerations for Dialysis (GFR 8, Cr 7.02)

Hypoglycemia Risk Management:

• Insulin requirements decrease by 25-50% in advanced CKD/dialysis due to reduced renal insulin clearance and decreased gluconeogenesis 4, 5
• However, the prednisone effect counterbalances this reduction, making the above doses appropriate 1
• Monitor glucose every 4-6 hours initially to identify patterns 4, 1

Dialysis Day Adjustments:

• Reduce NPH dose by 20% on dialysis days if hypoglycemia occurs, as dialysis can lower glucose 5
• Keep fast-acting carbohydrates available during and after dialysis 5

Conservative Titration Required:

• If hypoglycemia (<70 mg/dL) occurs, immediately reduce the corresponding insulin by 10-20% without waiting 1
• Increase doses by only 2 units every 3 days if hyperglycemia persists 1
• The combination of dialysis and steroids creates unpredictable insulin needs requiring close monitoring 4, 5

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Monitoring Protocol

Check blood glucose before each meal, at bedtime, and at 2-3 AM for the first 3 days to identify the characteristic "midday to midnight" hyperglycemia pattern of prednisone. 4, 1

Target Ranges:

• Fasting glucose: <130 mg/dL 1
• Daytime glucose: 140-180 mg/dL 4, 1
• Avoid glucose <100 mg/dL given dialysis status 4

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When Prednisone is Tapered

Reduce NPH by 10-20% for each significant steroid dose reduction to prevent hypoglycemia. 1, 3

• If prednisone decreases to 20 mg, reduce NPH to 16-20 units 1
• If prednisone is discontinued, consider switching back to Lantus at 50-60% of the peak NPH dose 1

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Common Pitfalls to Avoid

• Do not continue Lantus alongside NPH—this doubles basal insulin and causes severe hypoglycemia 1
• Do not use correction insulin alone without basal coverage—this reactive approach leads to poor control and more complications 4
• Do not give NPH at bedtime for morning prednisone—timing mismatch causes nocturnal hypoglycemia and daytime hyperglycemia 2
• Do not forget to adjust insulin downward as steroids taper—this is the most common cause of severe hypoglycemia in this population 1, 3
• Watch for the "midday to midnight" hyperglycemia pattern—if NPH alone doesn't control this, consider splitting to 2/3 morning and 1/3 evening 1