 This article deals with assessment of accuracy of the widely used glucose sensors MMT-7002 (Medtronic, USA), for continuous monitoring of glucose levels. The samples were gained from a 35-year-old sportswoman with diagnosed DM type 1. The sampling was carried out by her common daily as well as extreme physical and sport activities. The evaluated data were collected during 45 months, 56 sensors were used and 603 calibrations were carried out. The tested glucose sensor operates on the principle of a needle sensor, which electrochemically evaluates the reaction products catalyzed by glucose oxidase. Accuracy was evaluated by Clarke error grid analysis and the results were compared with the accuracy given by the sensor manufacturer. The measurements carried out by the tested sensor in the range of the normal glucose levels, realized under usual life conditions and by sport activities were even more accurate than those given by the manufacturer. However, in the regions of hypoglycemia or hyperglycemia, the number of errors was higher than specified by the manufacturer. The continuous glucose monitoring proved to be sufficiently accurate for prevention of acute complications in patients with DM type 1 during their common as well as extreme sport and physical activities.