Abstract: Objective To determine the effect of renal anemia on the glycosylated hemoglobin A1c (HbA1c)in patients with diabetes mellitus (DM) and patients without DM. 
Methods A total of 165 patients with renal anemia treated in General Hospital of Tianjin Medical University to including 67 patients with simple renal anemia and 98 with DM and renal anemia, were respectively analyzed. Correspondingly, the control group included 160 healthy controls and 272 patients with simple DM. Blood routine, fasting plasma glucose (FPG) and HbA1c of the four groups were collected and statistically explored. 
Results The FPG of the simple DM group and the DM and renal anemia group was 6.80(2.90) mmol/L and 6.30(3.40) mmol/L respectively, showing no significant difference (Z=-1.420, P=0.156). The HbA1c levels of the simple DM group and DM and renal anemia group were 7.50(2.10%) and 6.50(1.8)% respectively. The HbA1c of the DM complicated with renal anemia were significantly lower than that of the simple DM (Z=-6.195, P<0.001) and absolute difference was 1.0%. In addition, there was a positive correlation between HbA1c and hemoglobin levels in DM patients (r=0.294, P<0.001). Both the FPG and the HbA1c levels were significantly lower in the simple renal anemia group than in the healthy control group (both P<0.05). There was no significant difference in the ratio of FPG to HbA1c between the two groups (Z=-0.835, P=0.404). Furthermore, the correlation between FPG and HbA1c (r=0.618, P<0.001) was significantly lower in the moderate to severe anemia group than in the healthy control group (r=0.718, P＜0.001), while the correlation did not decrease in the mild anemia group. 
Conclusion Renal anemia can significantly decrease the HbA1c in DM patients, so that HbA1c cannot truly reflect the blood glucose level of patients. Therefore, the results of HbA1c detection in patients with DM and renal anemia should be treated with caution. Renal anemia patients without DM have lower blood glucose levels than normal people, and monitoring their long-term blood glucose levels with HbA1c does not make the results unreliable. 

Key words: diabetes mellitus, renal anemia, glycosylated hemoglobin