The article presents an analysis of practical experience and the author presents the methodology of glycolized hemoglobin (GH) determination in the clinic of internal diseases. 1220 patients with diabetes mellitus (DM) and without clinically evident DM have been examined during different period of time. Different techniques were used to determine GH. they are the following: photocolorimetric, chromatographic, and electrophoretic. It were useful during interpretation of GH to consider not absolute value of GH, but also change of its level in dynamics for a long period of time, i.e., art monitoring.