To investigate the relationship between blood glucose level, blood glucose variability and glycated hemoglobin A1_c (HbA1_c) in patients with type 2 diabetes.

A total of 240 patients with type 2 diabetes who were admitted to the Endocrinology Department of People′s Hospital of Karamay from March 2019 to April 2020 were selected. Based on the HbA1_c level, 240 patients were divided into 4 groups, Q1(5.5%-6.8%)(n=60), Q2(6.9%-7.9%)(n=55), Q3(8.0%-9.0%)(n=62) and Q4(9.1%-14.0%)(n=63). The continuous blood glucose monitoring system (CGMS) was used for continuous 72 h dynamic blood glucose monitoring.With HbA1_c as the dependent variable, and parameters related to HbA1_c as the independent variable, multiple linear regression method was used for regression analysis.

The fasting and 2 h postprandial plasma glucose levels in the Q1-Q4 groups were 5.92(4.81, 6.64)mmol/L and 10.27 (8.79, 12.34)mmol/L, 6.37 (5.49, 8.49)mmol/L and 12.02 (9.98, 15.27)mmol/L, 8.45(6.78, 9.97)mmol/L and 14.45(11.51, 18.12)mmol/L, 10.16(8.09, 11.52)mmol/L and 16.08(12.47, 19.27)mmol/L, respectively. The mean values of dynamic blood glucose for 72 h in the 4 groups were 7.41(6.71, 8.14)mmol/L, 8.20(7.40, 9.30)mmol/L, 8.91(7.93, 10.35)mmol/L and 10.36(9.12, 11.79)mmol/L, respectively. The average fasting blood glucose and 2 h postprandial glucose of the 4 groups increased with the increase of HbA1_c, and the differences between the groups were statistically significant (H=81.35, 37.26, all P<0.05). Fasting and 2 h postprandial blood glucose, the average value of 72 h dynamic blood glucose, the time percentage of dynamic blood glucose >10.0 mmol/L, the time percentage of dynamic blood glucose >7.8 mmol/L and standard deviation of blood glucose levels (SDBG) were correlated with HbA1_c (P<0.05), and the correlation coefficients were 0.68, 0.46, 0.63, 0.59, 0.42 and 0.36, respectively. The multiple linear regression analysis results showed that the average values of 72 h dynamic blood glucose and fasting glucose were HbA1_c′s independent impact factors (B=0.23, 0.53, all P<0.05).

The blood glucose variation has no effect on HbA1_c. The levels of fasting blood glucose and mean blood glucose are the main affecting factors of HbA1_c.