The paper presents the study results of free-radical oxidation and detoxification system of functional status in the rats after injection in diet cadmium chloride and water with a modified isotopic composition. The cadmium intoxication leads to oxidative stress, mainly in homogenates of liver and heart, what is characterized by increasing intensity of chemiluminescence and strengthening of cytolysis on 105-176%. Changing the isotopic composition of the diet resulted in a significant reduction of deuterium in the blood and tissues of the experimental group of animals, which was accompanied by a decrease in intensity of free-radical processes in blood on 11,2% and heart and liver homogenates on 38,1 and on 20,5 %, respectively (p<0,05), this became less pronounced destruction of hepatocytes, which decreased by 43%. The significant influence of a diet with the modified isotopic composition on the carbohydrate metabolism and the system state of non-specific protection kidney wasn’t revealed. The results indicate the development of cytoprotective effect in tissues with high metabolic indices in strengthening reactions isotope exchange in conditions of introduction in the diet with reduced water content of deuterium.