A 20-year-old male with T1DM (8-year history) is on mixed insulin therapy (short-acting and long-acting insulin) with subcutaneous injections before breakfast and dinner. Recent 2-week blood glucose monitoring shows fasting blood glucose (FBG) of 13.2-16.7 mmol/L, pre-lunch 8.0 mmol/L, pre-dinner 7.6 mmol/L, and bedtime 5.1 mmol/L. To optimize FBG control, which measure should be taken?