Insulin Dose Adjustment for a 72-Year-Old Male with Impaired Renal Function
For this 72-year-old male with impaired renal function (GFR 55) currently on 17 units of NPH insulin and requiring an additional 12 units of Novolog, the NPH dose should be increased by 12 units to a total of 29 units daily, administered as a twice-daily regimen with 2/3 (19 units) in the morning and 1/3 (10 units) in the evening.
Assessment of Current Insulin Requirements
- The patient's total daily insulin requirement is currently 29 units (17 units NPH + 12 units Novolog) 1
- With a BMI of 26 and weight of 87 kg, the current total daily dose is approximately 0.33 units/kg, which is a moderate dose 1
- The patient has impaired renal function (GFR 55), which increases the risk of hypoglycemia and requires careful insulin dosing 2
- The patient's preference to avoid carbohydrate counting and correction doses should be respected while ensuring adequate glycemic control 3
Recommended NPH Adjustment Strategy
- Convert the total daily insulin requirement (29 units) to a twice-daily NPH regimen 1, 3
- Distribute the NPH in a morning-weighted pattern with 2/3 in the morning and 1/3 in the evening 1, 3
- Morning dose: 19 units (2/3 of 29 units)
- Evening dose: 10 units (1/3 of 29 units)
Rationale for Twice-Daily NPH Regimen
- For patients requiring both basal and prandial coverage who don't want to carb count, a twice-daily NPH regimen is recommended by guidelines 1
- NPH has an intermediate-acting profile with a peak at 4-6 hours, which can help cover both basal and some prandial needs 4
- Converting from a basal-bolus regimen to twice-daily NPH is supported by ADA guidelines when patients prefer simplified regimens 1, 3
Monitoring and Titration Recommendations
- Monitor fasting and pre-meal glucose levels to assess the adequacy of the NPH doses 1
- Use an evidence-based titration algorithm: increase by 2 units every 3 days until reaching fasting glucose goals without hypoglycemia 1
- If hypoglycemia occurs, determine the cause and reduce the corresponding dose by 10-20% 1
- Pay special attention to nocturnal hypoglycemia risk due to the patient's impaired renal function 2
Important Considerations for Renal Impairment
- Patients with impaired renal function have altered insulin pharmacokinetics and are at higher risk for hypoglycemia 2
- With a GFR of 55, insulin clearance may be reduced, requiring vigilant monitoring 2, 5
- Proper resuspension of NPH insulin before injection is critical to ensure consistent absorption and action 4
- Instruct the patient to tip or roll the insulin pen/vial 20 times before each injection to ensure proper mixing 4
Potential Pitfalls and How to Avoid Them
- NPH insulin has higher day-to-day variability compared to long-acting analogs, which may affect glycemic control 6, 4
- Improper resuspension of NPH can lead to significant variability in insulin action and unpredictable glucose levels 4
- The risk of hypoglycemia is increased in elderly patients with renal impairment, requiring careful monitoring 2
- Consider switching to a long-acting basal analog if the patient experiences problematic hypoglycemia on NPH 1, 6