Research on the mechanism of hormonal action, the action of substances that are essential for the regulation of the metabolic system in form of physiologically important reactions, serves to explain various biochemical processes in the body. Investigations on the mechanism of insulin action began very early, but it still has not been proven. Insulin is a hormone, secreted by the pancreatic beta cells under stimulation by glucose. It consists of two chains that are the result of post-translational modification known as proteolytic processing. It occurs in three conformations: monomer, dimer and hexamer, whereby the monomer is the active form, and hexamers are the storage form. Glucose, the main metabolite, stimulates the synthesis of insulin, and secretion of already stored insulin via exocytosis. Insulin has a very important role in the regulation of metabolic processes. Its action through tyrosine kinase receptors causes a cascade of reactions that ultimately catalyze the dephosphorylation of the target protein. Thus, insulin regulates the metabolism of carbohydrates, especially glucose, in a way that it encourages the entry of glucose into muscle and fat cells via GLUT4 transporters, and its further metabolism within the cell. Moreover, it encourages the uptake of glucose in the liver to create glycogen, as a reserve of glucose till the appearance of the fasted state. Insulin also influences fat metabolism by activating the synthesis of fatty acids from acetyl-CoA. Insulin is also called the satiety hormone, because all the processes that it encourages take place when the organism is in a state of affluence, what means that all body's needs are satisfied. As a consequence of adisorder in the metabolism of insulin is diabetes (diabetes mellitus), which is characterized as a chronic hyperglycemia (elevated blood sugar) because of impaired insulin secretion, insulin action or both. Due to this situation the patient's body is in a constant state of starvation because of the inability of glucose to enter the cells. However, changing the lifestyle at the very beginning, beforethe body has exhausted its own ability to produce insulin, a disorder in the blood glucose level is completely regressive, meaning that people can revert all health parameters to normal and maintain this state indefinitely, if they continue with a healthy diet and good living habits.