Aim: Biological variation (BV) of the HbA1c test can be affected by analysis method, sampling period, and disease activity. The aim of the present study was to examine the impact of CVI, CVA, and II for Tosoh G7 system. Material and Method: 96 samples from 12 healthy volunteers were collected for every two weeks during a two-month period. HbA1c levels of all samples were measured by G7 HPLC (non-porous ion-exchange) Analyser. Biological variation parameters CVI, CVA, CVG, RCV, and II were calculated. Results: The mean of HbA1c was 5.10% (32.3 mmol/mol). CVA was calculated as 2.81%. The CVI and CVG for HbA1c were 1.69% and 7.56%, respectively. RCV and II values were 9.08% and 0.22. Discussion: According to our results, the sampling period and study method were fundamental to determining biological variation parameters. When using the Tosoh G7 system, we observed similar results to other methods, e.g. boronate affinity or immunoturbidimetry. Low individuality index of HbA1 c presented that the analyte had marked individuality and that the population-based reference values had low utility for disease monitoring. Thus, estimation and inclusion of RCV in laboratory reports for HbA1c will guide the clinicians in evaluating the importance of difference between serial results and glycemic status of the patients.