According to the sanocreatological nutrition theory, the role of nutrition consists not only in supplying the organism with the necessary energy and plastic substances but also in the formation and maintenance of the health. The significance of nutrition as a determinant factor in health insurance and disease prevention is enhanced with the development of sanocreatology, as it is the most frequent factor influencing on the organism. So far the present is no unanimously accepted opinion on the structure and content of food ration in the period of degradation of the organism. It is believed that with age, the amount of protein administered should be reduced, but it is well known that catabolic processes predominate during this period, which determines the process of degradation. According to sanocreatology, the prevention of early degradation of the organism is possible by increasing anabolism on the background of intensive catabolism to get the balance of these processes by increasing the amount of protein in the food ration. Because testosterone, being an anabolic hormone, primarily influences the protein metabolism, it has been necessary to study its influence on this metabolism, an indicator of which the content of free amino acids in serum can be used. The purpose of the research was the determination of the particularities of the change of the content of free amino acids in the blood of old rats fed with different rations in association with testosterone.  The investigations were performed on white old laboratory rats (males - 24-30 months), divided into 3 experimental groups: the first group – ration standard (15% - proteins, 60% - cardohydrates, 25% - lipids), group 2 – with high-protein ration (25% - proteins, 55% - cardohydrates, 20% - lipids), group 3 – with ration rich in cardohydrates (70% - cardohydrates, 10% - proteins, 20% - lipids).The experiments with testosterone (TS) administration were achieved on similar animals distributed in 3 groups: standard ration in association with TS, ration rich-protein in association with TS and ration rich in carbohydrates in association with TS. The TS administration was performed intramuscularly daily (solution of TS propionate), individually, according to body mass (0,1 mg/100 g body weight), the dose is changed weekly with its change. Duration of the experiment – 31 days. The content of free amino acids in the serum was determined by the ion-exchange liquid chromatography method.  Maintenance of old rats with ration with different content of constituent components has resulted in increasing the numerical value of most free amino acids in the serum, so we can admit that catabolic processes are increased and anabolic ones are diminished; while in association with TS, the change in the vector of the concentration of most amino acids has a downward character. That is to say, the ration with both high protein content and carbohydrate-rich content is possibly associated with the reduction of anabolism, and the standard ration in association with TS – with the reduction of both anabolism and catabolism. We will note that the total amino acid content decreased in the serum of old rats in combination with TS in association with different rations in all three groups compared to the animals without TS administration maintained with the same ration. Therefore, the comparative analysis of the influence of rations with the different structures on the content of free amino acids in the serum of old rats shows the decrease of the anabolic processes, especially in the case of protein-rich ration. The influence of different rations in association with TS on free amino acid content at old rats reveals the diminution of their anabolic processes, and in the case of carbohydrate-rich ration – catabolic processes are clearly expressed.