The aim of the preset study was to investigate the effectiveness of structured self-monitoring of blood glucose (SMBG) in insufficiently controlled insulin-treated diabetes. A total of 86 insulin-treated patients were randomized to a routine testing group (RTG; n = 43) and a structured testing group (STG; n = 43). The STG used a chart to record seven-point blood glucose (BG) profile on three consecutive days per month. The primary end-point was the glycated hemoglobin (HbA1c) at 3 months and 6 months. There were no significant differences of HbA1c between the RTG and STG at 3 months. However, the STG had significantly improved HbA1c at 6-month follow-up compared with the RTG (P = 0.002). In the STG, HbA1c decreased by 0.5% from 7.9 (SD 0.5) to 7.4 (0.7)%, whereas it decreased by 0.1% in the RTG from 7.9 (0.5) to 7.8 (0.7)%. In the STG, 55% of the patients were willing to continue structured SMBG and they achieved a 0.7% decrease of HbA1c. The present findings suggest that structured SMBG significantly improves glycemic control.