The results of a biochemical blood test on the 20th and 40th day after infection of the Diphyllobothrium latum had a little changes in some indicators, which in general did not have significant diagnostic significance. A decrease in the level of vitamins is noted in dogs infected with a broad tapeworm on the 20th and 40th day after the invasion. In all cases, a more pronounced decrease in vitamin levels (A, E, C) depended on the timing of observation of infected dogs. The lowest levels of vitamins A, E, C are noted on the 40th day after the invasion and amounted to: vitamin E - 23 %, vitamin A - 17.2 %, vitamin C - 27.3 %. Despite the general dynamics of the decrease in vitamins levels (A, E, C) in infected dogs with broad tapeworm, this decrease was more pronounced when monitoring the content of vitamin C in contrast to the rest. On the 20th day of the invasion, an increase in the level of enterokinase is noted, in contrast to the indicators of the control group. In the study of enterokinase on the 40th day of infection, the enterokinase index continued to increase and amounted to 12 ± 0.24. A marked increase in the enterokinase index in dogs infected by Diphyllobothrium latum will signal the suppression of secretory activity of the intestine.