Conceptual question of the blood losses connected with phenomenon of endotoxicosis is being studied in this work. For this purpose an adapted method of the patients' blood having blood losses was used. It was realised on the white rat's vein porta. Ten patients with different kinds of haemorrhage being investigated, the presence of toxic traces in the blood taken from the patients in the first days of the posthaemorrhagic period are evident. The date of the blood toxic are normalised on the tenth-fourteenth day of the posthaemorrhagic period. Toxic features of the patients' blood with blood losses are proved by the investigations of leucocyte index intoxication in the first day of the posthaemorrhagic period. Twenty patients were investigated by that. The received results proved the presence of endotoxicosis in the patients' having blood losses.