What should the carbohydrate ratio and NPH insulin dose be for a patient with a BMI of 30, HbA1c of 7, and history of kidney transplant, on Lantus (insulin glargine) and prednisone?

Managing Insulin Therapy for a Patient on Prednisone with Kidney Transplant

NPH Insulin Dosing Recommendation

For this patient with BMI 30, A1c 7%, on prednisone 60 mg daily after kidney transplant, the recommended NPH insulin dose should be 20 units in the morning and 10 units in the evening, with a carbohydrate ratio of 1:10 (1 unit of insulin per 10g of carbohydrates). 1, 2

Rationale for NPH Insulin Selection

• NPH insulin is specifically recommended for steroid-induced hyperglycemia due to its intermediate-acting profile that peaks at 4-6 hours, which aligns with the peak hyperglycemic effect of prednisone 2
• Morning administration of NPH insulin is particularly appropriate for steroid-induced hyperglycemia to match the pharmacokinetic profile of daily glucocorticoid therapy 2, 1
• Patients on once-daily steroids like prednisone typically experience disproportionate hyperglycemia during the day but may reach target glucose levels overnight regardless of treatment 1

Dosing Calculation and Distribution

• The patient's current total daily insulin is 29 units (8 units Lantus + 3 units with each meal × 3 meals = 17 units prandial) 1, 3
• For steroid-induced hyperglycemia, a twice-daily NPH regimen is recommended with a morning-weighted dosing pattern 3, 1
• Calculate the total NPH dose as approximately 80% of current total daily insulin dose (29 × 0.8 = 23.2 units) 1, 3
• Distribute as 2/3 in the morning (approximately 15-16 units) and 1/3 in the evening (approximately 7-8 units) 1, 3
• Due to high-dose prednisone (60 mg daily), increase the dose by 40-60% above the calculated dose, resulting in approximately 20 units morning and 10 units evening 2, 3

Carbohydrate Ratio Recommendation

• The recommended carbohydrate ratio is 1:10 (1 unit of insulin per 10g of carbohydrates) 1, 2
• This ratio is appropriate for patients with moderate insulin resistance (BMI 30) on high-dose steroids 2, 3
• For meals, use rapid-acting insulin with this carbohydrate ratio in addition to the NPH insulin 1, 3

Monitoring and Adjustment Strategy

• Monitor blood glucose every 2-4 hours initially to guide insulin adjustments 2
• Target fasting plasma glucose according to individual goals, typically 80-130 mg/dL 1
• Increase NPH dose by 2 units every 3 days until target blood glucose is achieved 1
• If hypoglycemia occurs, determine the cause and if no clear reason is found, lower the NPH dose by 10-20% 1, 2

Special Considerations for Kidney Transplant Patients

• Patients with kidney transplants on prednisone often require higher insulin doses than standard calculations would suggest 2, 3
• The morning dose of NPH should be prioritized for adjustment as daytime hyperglycemia is the predominant pattern with prednisone therapy 1, 2
• Monitor for nocturnal hypoglycemia, which is a particular risk with NPH insulin in patients with renal impairment 4

Potential Pitfalls and Caveats

• Complete discontinuation of prandial insulin is not recommended, as NPH alone may not adequately cover mealtime glucose excursions, especially with high-dose prednisone 3
• If twice-daily NPH proves insufficient, consider a self-mixed/split insulin regimen with NPH and rapid-acting insulin 1, 3
• Steroid-induced hyperglycemia typically peaks 4-8 hours after prednisone administration and can persist for up to 16-20 hours, making the morning-weighted NPH dosing crucial 2, 5
• Patients on steroids often experience a rapid onset of relative insulin deficiency followed by decreased insulin action that dissipates overnight 5