In acute gastrointestinal diseases in calves lead to endogenous intoxication (self-poisoning of the body with toxic metabolic products and tissue breakdown). The aim of this study was to investigate the pathogenesis of endotoxemia in calves with dyspepsia and it's correction with the herbal preparation Hyperico. To assess endotoxemia, we measured the concentration of medium-sized molecules in serum and blood biochemical parameters (total protein and albumin levels, bilirubin, creatinine, urea, glucose, and enzyme activity). Postdocs the severity of clinical signs of intoxication, depression, and diarrhea in calves of the experimental group decreased within 24 hours. In patients calves before administration of Hyperico, the levels of total protein, albumin, glucose, and AST enzyme activity were significantly lower than in clinically healthy animals of the control group by 38.3%, 36.3%, 60.5%, and 45.1%, respectively. Total urea and ALT levels increased by 95.2 and 123.7%, respectively, while bilirubin levels increased by 43.4%. SM levels at 254 nm and 280 nm were 0.41 conventional units. These values were significantly higher than in the healthy calf group by 74.3 and 51.9%, respectively. The results indicate the occurrence of metabolic and functional disturbances in the body's systems, leading to endogenous intoxication. Five-day administration of the drug to calves did not result in toxicosis in test animals. Full recovery of the calves occurred on the tenth day. Hyperico has an antitoxic and therapeutic effect.