). It is shown that an the first month of water intake the renal response of osmoregulatory mechanisms is activated, and by the sixth month the differences are smoothed out, to a greater extent indicating the adaptation of the organism to ion loads. At the first stage (3 months)the more pronounced changes in ionuretic response were observed following intake of water with higher content of Mg 2+ , at thesecond stage (6 months) -Ca 2+ .In rats of the two experimental groups the concentration of the stress hormone, cortisol and thyroid hormones decreased, which may indicate depletion of theregulatory mechanisms as a result of prolonged stress of hormonal system. Keywords: drinking water, calcium, magnesium, rats, blood plasma, kidney function, hormones.