Currently, a serious consequence of environmental degradation is the significant deterioration of the health of the population, accompanied by an increase in the number of exogenous poisonings. A simple and effective method of detoxifying the human body is the enterosorption. In the case of enterosorption, endogenous and exogenous metabolites of the digestive tract are subsequently immobilized and eliminated from the digestive tract. Presently, the method of detoxification of the human body widely used in most of the clinics is the enterosorption and the most applied enterosorbents are made from activated carbon. A special role in this regard belongs to the activated carbons obtained from walnut shells, fruit seeds, grape seeds. Due to the adsorption forces, in the porous structures of activated carbons (in the volume of micropores and mesopores) the adsorption of different types of contaminants takes place. The high adsorption properties of these activated carbons offer wide possibilities for their use, including in the complex treatment of intoxications and pathological conditions. For research, the activated charcoal obtained in the laboratory was selected from: charcoal (CA-ML), walnut shells (CAN), peach kernels (CA-23), plum kernels (CA-35), intact apple wood and reactivated (CAM and CAM-30), but also a sample of commercially activated carbon (Granucol BI). Vitamin B12 (Cyanocobalamin) with MM 1355.38 u.c. was used as a marker substance (fig. 1) which models the situations of intoxication of the human body with toxins with medium molecular weight (MM 500-1500), such as oligopeptides, lipopolysaccharides, etc. Figure 1. Vitamin B12 (C63H88CoN14O14P In this paper, the adsorption of Vitamin B12 on several samples of activated carbons mentioned above was studied. The kinetic adsorption curves were determined from 0.5 h to 48 h with the initial concentration of the solutions 200 mg/L, at a temperature of 250ºC. The data obtained indicate that the degree of immobilization of Vitamin B12 on the activated carbon samples investigated, increases with increasing contact time between the two phases, and the balance is established within 20-24 h. The adsorption effect of Vitamin B12 is obviously different depending on the nature of the adsorbent and there is a big increase in adsorption when reactivated for 30 minutes from 20 mg/g in the case of CAM (activated charcoal obtained from apple wood) to 180 mg/g for CAM-30 sample (same activated carbon with an additional activation of 30 min under the same conditions). The researched carbons show increased immobilization capacities of the marker substances (Vitamin B12), and for the reactivated samples the values are 5-6 times higher than the intact samples.