Water is the main part of the human body and it is distributed throughout every cell, tissue and organ. Most of the organs contain more than 70% of the water and the largest part of the water is placed in our blood and kidneys. Water represents about 60% of the body weight. Water is distributed in two main sections: intracellular and extracellular. Intracellular section is the largest and it presents about two-thirds body water, while extracellular section presents one-third of the body water. Physiological roles of body water are very important to our lives. Water is necessary for our life and for maintaining optimal hydration levels. The water balance is affected by the foodweeat, by the level of our physical activity, our age and environmental conditions. That implies precise regulation of the water balance during 24 hours as well as proper water intake and loss. Dehydration is the process of losing water from the body. Depending on the electrolyte concentration in the water, there are 3 types of dehydration: isotonic, hypertonic and hypotonic dehydration. World Health Organization (WHO) classify dehydration on 3 other types : mild, moderate and heavy. Hydration refers to the possession of a sufficient amount of fluid in body tissues and it can be determined by different methods. Methods that are used for determining hydration are: subjective, objective and laboratory method. The recommended daily water intake is 1,5-2 L. K