What is the appropriate NPH (Neutral Protamine Hagedorn) insulin dose for an 83-year-old female patient with type 2 diabetes, body mass index (BMI) of 42, and weight of 109 kg, who is receiving methylprednisolone (methylpred) 250 mg intravenously (IV)?

NPH Insulin Dosing for Steroid-Induced Hyperglycemia

Start NPH insulin at 22 units subcutaneously every morning to match the peak hyperglycemic effect of methylprednisolone 250 mg IV. 1, 2

Rationale for NPH Selection and Dosing

NPH insulin is the preferred formulation for steroid-induced hyperglycemia because its intermediate-acting profile peaks at 4-6 hours, which specifically aligns with the peak hyperglycemic effect of methylprednisolone. 1, 2 Morning administration is critical to match the pharmacokinetic profile of glucocorticoid therapy. 1, 2

Dose Calculation

• Initial NPH dose: 0.2 units/kg/day for this patient with advanced age (83 years), obesity (BMI 42), and high-dose steroid therapy. 1, 2
• Calculation: 0.2 units/kg × 109 kg = 21.8 units, rounded to 22 units administered subcutaneously in the morning. 1
• This represents a conservative starting point given the patient's age >65 years, which increases hypoglycemia risk. 3

Why This Dose is Appropriate

High-dose glucocorticoids (methylprednisolone 250 mg IV) typically increase insulin requirements by 40-60% above standard dosing. 2 However, the 0.2 units/kg starting dose accounts for:

• Advanced age (83 years): Older patients require lower initial doses due to increased hypoglycemia risk. 3
• Obesity (BMI 42): While obesity increases insulin resistance, the dose is calculated on actual body weight. 1
• Type 2 diabetes with preserved endogenous insulin: Most type 2 diabetes patients maintain some beta-cell function, requiring less aggressive dosing than type 1 diabetes. 3

Complete Insulin Regimen

Basal-Bolus Approach

Continue or add a basal-bolus regimen alongside NPH:

• Basal insulin: If not already on basal insulin, start long-acting insulin (glargine or detemir) at 0.1-0.2 units/kg at bedtime for overnight coverage. 3
• Prandial insulin: Add rapid-acting insulin (lispro, aspart, or glulisine) before meals using a carbohydrate ratio of 1:10 initially (1 unit per 10g carbohydrate). 2
• Correction scale: Use 1 unit of rapid-acting insulin for every 40-50 mg/dL above target glucose of 150 mg/dL, with more aggressive correction in afternoon/evening when steroid effect peaks. 2

Monitoring Protocol

• Blood glucose monitoring: Check before each meal and at bedtime, with additional checks every 2-4 hours initially during steroid therapy. 2
• Target range: 140-180 mg/dL for hospitalized patients, though 100-140 mg/dL may be considered if hypoglycemia risk is minimal. 3
• Dose adjustments: Modify NPH dose every 2-3 days based on glucose patterns. 1

Critical Safety Considerations

Hypoglycemia Risk

• Basal-bolus regimens carry 4-6 times higher hypoglycemia risk than correction insulin alone, particularly concerning in elderly patients with renal considerations. 1
• Nocturnal hypoglycemia is a major concern due to NPH's prolonged duration of action. 1
• If hypoglycemia occurs, reduce the corresponding insulin dose by 10-20%. 4

Steroid Tapering

• As methylprednisolone is tapered, reduce NPH by 10-20% with each steroid dose reduction to prevent hypoglycemia. 1
• Insulin requirements typically decrease rapidly after steroid discontinuation, requiring prompt dose adjustments. 2
• Adjust carbohydrate ratio from 1:8 toward 1:10 as steroid doses decrease. 1

Common Pitfalls to Avoid

• Do not rely solely on long-acting insulin without adding NPH, as this leads to inadequate coverage of daytime steroid-induced hyperglycemia. 2, 5
• Do not use sliding scale insulin alone in patients with established diabetes, as this is associated with clinically significant hyperglycemia. 3
• Monitor closely for ketoacidosis in patients receiving high-dose steroids, as this can occur even with insulin therapy. 6
• Expect 2-fold peak glucose increases approximately 10 hours after each methylprednisolone dose. 6