Objective. To determine threshold values of critical laboratory test results in patients with urgent conditions. Material and methods. Analytes were selected from the diagnostic panel of laboratory analyzer of urgent conditions. Thirty anesthesiologists and resuscitators were interviewed to determine the threshold levels of critical values for the proposed analytes. In addition, we made a review of the literature devoted to this issue. The results published in the literature and those obtained from the specialists were compared to determine the threshold values. Thereafter, we carried out a retrospective analysis of all laboratory tests results for selected analytes for 2018 at the St. Petersburg City Multi-Field Hospital №2. Results. The maximum differences were found on the upper threshold value of calcium level (20%). Differences for the lower and upper pH threshold were 2% and 1%, respectively. Retrospective analysis included 110 962 results of laboratory tests. There were 6915 (6.2%) critical values observed in analysis of threshold values in the literature. There were 7167 (6.5%) critical values obtained in questionnaire survey of anesthesiologists and intensive care physicians of the St. Petersburg Clinical Hospital №2. We obtained 6795 (about 18 per day) and 5393 (about 15 per day) blood samples respectively which contain the critical values of analytes. Conclusion. Introduction of «critical values» concept requires the personification of threshold values considering the profile of clinical departments. Development of standard operating procedures in this area should be carried out with the mandatory participation of specialists from clinical and laboratory departments