He has not recently changed his insulin regimen or meal plan. He wants his diabetes to be "well controlled" and exercises regularly, although he notes less exercise recently because of increased fatigue. He currently takes insulin glargine 22 U at bedtime and between 5 to 7 U of insulin aspart before each meal.

His blood pressure is 100/60 mm Hg sitting. Laboratory results are significant for a serum sodium concentration of 130 meq/L (130 mmol/L), a serum potassium concentration of 5.2 meq/L (5.2 mmol/L), and a hemoglobin A1c value of 6.5%. Other laboratory findings include a serum creatinine concentration of 0.9 mg/dL (79.58 µmol/L) and a blood urea nitrogen concentration of 30 mg/dL (10.71 mmol/L).

QUESTION:

Which of the following is the most likely contributor to the increased frequency of hypoglycemia?

A. Development of Addison's disease

B. Development of renal impairment 

C. Presence of thyrotoxicosis 

D. Excess insulin dosing to try to achieve better glucose control