Objective To investigate the relationship of serum level of 1,5-anhydroglucitol (1,5-AG) with mean 24-hour blood glucose and glycemic excursion in the aged patients with type 2 diabetes mellitus (T2DM), and to explore whether serum 1,5-AG can be used as one of the indicators for the clinical observation and treatment of the disease. Methods Totally ninety-five aged T2DM inpatients, 65 males and 30 females, with age ranging from 70 to 80 (80.1±4.3) years, who were admitted in our department from July 2009 to July 2012, were enrolled in this study. They were uniformed for their mealtime, and monitored for blood glucose for 3 consecutive days with a continuous glucose monitoring system (CGMS). Their reference blood glucose, diet, times of taking medicine and doing exercises were recorded. Venous blood sample was collected on the 3rd day for the analysis of 1,5-AG, glycated hemoglobin (HbA1c), and glycosylated serum protein (GSP) after 8 hours fasting. Results The serum level of 1,5-AG was negatively correlated with fasting blood glucose (FBG), 2-hour postprandial blood glucose, HbA1c, GSP, mean blood glucose (MBG) within 3d, and mean amplitude of glycemic excursions (MAGE) (all P＜0.05). Pearson correlation analysis indicated that the serum level of 1,5-AG had a negative correlation with MBG at the 6 time points of a day: 1h before breakfast, 2h after breakfast, 3h after breakfast, 2h after dinner, 3h after dinner, and 2∶00 am to 4∶00am (all P＜0.05), but the level had no relation with MBG at other time points. Conclusion Serum level of 1,5-AG makes sound reflections of MBG and glycemic excursion within a short period, and can be considered as one of the indicators for diabetic screening and clinical monitoring for treatment.