The percent of variations of glycosylated haemoglobin before and after rapid glycemic increases inducted in diabetics and healthy subjects are not significant (p greater than 0,05). The same results were obtained using both the chromatographic method on Bio-Rex 70 microcolumns and the colorimetric method with 2-thiobarbituric acid. The usefulness of HbA1c as a parameter in controlling the glycemic equilibrium is confirmed.