What is the recommended NPH (Novolin N (NPH) insulin) dose and carb ratio for a patient with no history of diabetes, receiving a 3rd dose of methylprednisolone (methylprednisolone) 1000mg, weighing 68kg and having a BMI (Body Mass Index) of 25?

NPH Insulin Dosing for Steroid-Induced Hyperglycemia in Non-Diabetic Patients

For a non-diabetic patient receiving a 3rd dose of methylprednisolone 1000mg with weight 68kg and BMI 25, the recommended starting NPH insulin dose is 0.3 units/kg/day (approximately 20 units total), with 2/3 (about 14 units) given in the morning and 1/3 (about 6 units) in the evening, along with a carbohydrate ratio of 1 unit of insulin for every 10-15g of carbohydrates consumed. 1

Rationale for NPH Insulin Selection

• NPH insulin is specifically recommended for steroid-induced hyperglycemia due to its pharmacokinetic profile that matches the hyperglycemic effect of intermediate-acting glucocorticoids 1
• High-dose methylprednisolone causes significant hyperglycemia even in non-diabetic patients, with studies showing glucose increases from baseline of 83 mg/dL to 140-183 mg/dL after steroid pulses 2
• NPH insulin should be administered concomitantly with intermediate-acting steroids as its peak action occurs at 4-6 hours after administration, coinciding with the peak hyperglycemic effect of steroids 1

Dosing Algorithm

1. Initial NPH dose calculation:

   • Starting dose: 0.3 units/kg/day = 0.3 × 68kg = 20.4 units (round to 20 units) 1
   • Morning dose (2/3 of total): 14 units
   • Evening dose (1/3 of total): 6 units

2. Timing of administration:

   • Administer NPH insulin every 8-12 hours 1
   • For once-daily morning steroid therapy, NPH should be given in the morning with the steroid dose 1

3. Carbohydrate coverage:

   • Use 1 unit of insulin for every 10-15g of carbohydrates 1
   • For meals, add rapid-acting insulin using this carbohydrate ratio

Blood Glucose Monitoring and Dose Adjustment

• Monitor blood glucose before meals and at bedtime 1
• Expect highest glucose levels to occur in the afternoon and evening after morning steroid administration 1
• Adjust NPH dose by 2-4 units every 1-2 days based on glucose patterns 3
• Target blood glucose range: 100-180 mg/dL 1

Special Considerations

• Methylprednisolone causes more significant hyperglycemia compared to prednisolone or hydrocortisone (mean difference of 27.4 mg/dL higher) 4
• Higher steroid doses and longer duration of treatment increase diabetes risk - one study found 36.3% of non-diabetic patients developed diabetes with high-dose methylprednisolone 5
• If enteral nutrition is interrupted, start 10% dextrose infusion immediately to prevent hypoglycemia 1
• Avoid relying solely on sliding scale insulin as it leads to poor glycemic control 3

Hypoglycemia Management

• Treat hypoglycemia with 15-20g of glucose and recheck after 15 minutes 3
• Risk of hypoglycemia increases overnight as steroid effect wanes 1, 6
• Have glucagon available for emergency hypoglycemia management 3

This approach balances the need to control steroid-induced hyperglycemia while minimizing the risk of hypoglycemia in a patient without prior diabetes history. The NPH insulin regimen should be adjusted daily based on glucose monitoring results.