Objective . To evaluate the frequency and factors associated with the development of fatigue among students of a medical university. Materials and methods . Fatigue Assessment Scale (FAS) was used to identify and quantify fatigue. To determine the level of active attention, the electronic number test was used. Assessment of students’ physical activity was carried out according to the degree of energy costs. Capillary blood ammonia levels were evaluated using a Pocket Chem BA PA 4140 handheld analyzer. Results . The median severity of fatigue according to the FAS questionnaire for students of the 5–6 year medical university was 23,0 (21,0–29,0) points. All students were divided into two groups depending on the level of scores on the FAS questionnaire. Pathological fatigue syndrome was identifi ed in 26 (65%) students. In 14 (35%) students, the FAS value was less than 22 points. in men, the level of fatigue corresponded to 21,0 (14,0–29,0) points, in women 23,0 (21,0–29,0) points, without reaching statistical signifi cance (p = 0,321). Among students of the fi rst group (FAS <22 points), the level of physical activity of the middle level was signifi cantly more likely to occur (p = 0,015). In this case, students with low physical activity diff ered signifi cantly higher values of both physical (14,0 (12,0–18,0)) and mental (11,0 (9,00–14,0)) FAS coefficients (p = 0,001 and p = 0,007). A decrease in BMI of less than 18.8 kg / m 2 is associated with an increase in the risk of pathological fatigue among medical students by 0,283 (95% CI 0,087–0,927), and a low level of physical activity by 0,179 (95% CI 0,042–0,753). Additionally, a correlation analysis revealed a negative relationship between the values of the FAS test and the level of the average student achievement score. The median ammonia concentration was 74,0 (66,0–99,0) μmol/L. Among students with capillary blood ammonia levels of more than 100 μmol/L, students with pathological fatigue predominated according to the FAS questionnaire (in 83,3% of cases), and there were no people with average physical activity (p = 0,062). Conclusions . 1. Students of the 5–6 th year of a medical university in 65% of cases have a high level of fatigue, which inversely correlates with academic performance. 2. Factors associated with pathological fatigue in senior medical students are body mass index less than 18,8 kg/m 2 (RR0,283 (95% CI 0,087–0,927)) and low level of physical activity (RR0,179 (95% CI) 0,042–0,753)). 3. For senior students of a medical university included in the study, the median concentration of ammonia of capillary blood was 74,0 (66,0–99,0) μmol / L; no signifi cant relationship was found between the concentration of ammonia of capillary blood and the level of fatigue.