What is the most appropriate adjustment to improve glycemic control in a patient with type 2 diabetes mellitus and elevated post-dinner glucose levels?

Adjusting Insulin Therapy for Post-Dinner Hyperglycemia

The most appropriate adjustment is to increase the pre-dinner dose of insulin lispro to 18 units SC to address the elevated post-dinner glucose values of 150-165 mg/dL.

Analysis of Current Glycemic Control

The patient's glycemic profile shows:

• A1c: 6.9% (near target)
• Fasting blood glucose: 88-122 mg/dL (well-controlled)
• Pre-lunch glucose: 82-126 mg/dL (well-controlled)
• Pre-dinner glucose: 66-112 mg/dL (well-controlled)
• 2-hour post-dinner glucose: 150-165 mg/dL (elevated)

This pattern clearly indicates that the primary issue is post-dinner hyperglycemia, while other glucose values throughout the day are relatively well-controlled.

Rationale for Increasing Pre-Dinner Insulin Lispro

The American Diabetes Association (ADA) and European Association for the Study of Diabetes (EASD) guidelines recommend adjusting prandial insulin doses based on postprandial glucose excursions 1. When basal insulin has been titrated to an acceptable fasting blood glucose level but postprandial excursions persist, the appropriate approach is to adjust the mealtime insulin for the specific meal causing the excursion 1.

The patient's current regimen includes:

• Metformin 1000 mg twice daily
• Insulin glargine 25 units SC at bedtime (basal)
• Insulin lispro 12 units SC before meals (prandial)

Since the post-dinner glucose values are consistently elevated (150-165 mg/dL) while pre-meal values are well-controlled, increasing the pre-dinner dose of insulin lispro is the most appropriate adjustment.

Why Other Options Are Less Appropriate

1. Decreasing pre-breakfast lispro to 6 units: This would likely worsen glycemic control as pre-lunch glucose values are already well-controlled. Reducing the breakfast dose could lead to higher pre-lunch values.

2. Decreasing pre-lunch lispro to 10 units: The pre-dinner glucose values are already well-controlled (66-112 mg/dL), with some values on the lower side. Decreasing the lunch dose could potentially lead to higher pre-dinner values.

3. Increasing insulin glargine to 35 units: The fasting blood glucose values are already well-controlled (88-122 mg/dL), indicating appropriate basal insulin dosing. Increasing basal insulin when the issue is clearly postprandial hyperglycemia would increase the risk of nocturnal and fasting hypoglycemia 1.

Implementation Strategy

When adjusting prandial insulin for postprandial hyperglycemia:

1. Increase the pre-dinner insulin lispro from 12 units to 18 units SC (a 50% increase)
2. Monitor 2-hour post-dinner glucose values for 3-7 days
3. Target post-dinner glucose values <180 mg/dL 1
4. If hypoglycemia occurs, reduce the dose by 10-20%

Important Considerations

• Risk of hypoglycemia: Monitor closely after increasing the insulin dose, particularly in the late evening hours 2
• Meal consistency: Ensure consistent carbohydrate content at dinner to avoid unexpected hypoglycemia 1
• Timing of injection: Administer insulin lispro immediately before meals for optimal effect 3
• Patient education: Teach the patient to recognize and treat hypoglycemia symptoms 4

Follow-up Plan

• Schedule follow-up in 2-4 weeks to assess the effect of the dose adjustment
• Consider further adjustments based on glucose monitoring results
• Reassess A1c in 3 months to evaluate overall glycemic control

The goal is to maintain the patient's good control throughout the day while specifically addressing the post-dinner hyperglycemia, which will likely improve overall glycemic control and potentially lower A1c further.