Hyperkalemia, or elevated potassium levels in the blood, can have a serious effect on the body. High potassium levels can be both a cause and a consequence of impaired cell function, including cells of the heart, nervous system, muscles and other organs. The purpose of the presented study was to identify and evaluate the etiological causes leading to the development of hyperkalemia in cats in St. Petersburg with subsequent statistical processing of the results obtained. The serum levels of total protein, albumin, globulin, urea, creatinine, bilirubin, glucose, potassium, calcium, phosphorus, sodium, chlorine, as well as the activity of the enzymes alanine aminotransferase (AlAt), aspartate aminotransferase (AsAt) and alkaline phosphatase were determined. The study of biochemical parameters was carried out according to generally accepted methods. It was revealed that the most common causes of hyperkalemia in cats include disorders of the urinary system (52%) – acute renal failure, less often chronic kidney disease, as well as diseases of the gastrointestinal tract (24%), oncological processes (19%). It was also revealed that the survival rate for 7 days after diagnosis was approximately the same in groups with different levels of hyperkalemia and amounted to about 60-67%, which indicates the rapid reversibility of adverse reactions resulting from hyperkalemia with timely intervention. In the future, the study is planned to expand with the capture and analysis of individual nosological units and breed characteristics, as well as dietary characteristics, the ratio to the severity of the condition, the analysis of life expectancy and survival.