Morphological changes in the pancreas and magnesium concentration in the bones and blood of adult male Wistar rats after daily administration of magnesium ions were studied. The rats were divided into two groups (12 animals each): I – control, II – rats, which daily (for 21 days) received magnesium chloride in a dose of 50 mg / kg. At the end of the experiment we observed a significant increase in the magnesium concentration in the tibia, serum and erythrocytes in the experimental rats by 36, 16 and 17 %, respectively. It was found that administration of magnesium chloride led to morphological changes in the exocrine part of the pancreas, indicating an increase in its activity. Thus, in the gland of experimental rats, we detected exocrine cells of an increased size. The sizes of their nucleus and cytoplasm as well as the number of nucleolus in the nucleus were also increased. The influence of magnesium chloride significantly increased the activity of the endocrine pancreas. This was indicated by the following morphological changes: an increase in the relative area of the endocrine part (by 19 %), the ​​ size of the Langerhans islets, an increase in the number (by 54 %) and density (by 20 %) of the endocrinocytes housed in them compared to the control. Thus, the obtained morphological results indicate that the introduction of magnesium enhances the exo- and endocrine function of the pancreas.