Introduction It is the universally accepted truth that correct nutrition, diets, enough exercise and the quite active ways of life are the factors that predetermine the healthy living of a person. Different scholars express various opinions on the issue of what products, minerals, vitamins, etc. are the most useful for human beings in certain climatic, geographical, health and activity conditions (Grosvenor and Smolin, 2005). Nevertheless, all the scholars dealing with human health agree on the statement that water is the most important, or even vital, element of nature that makes the very existence of human beings possible and creates the necessary balance of microelements and minerals inside of the human organism. Dehydration, on the other hand, is the state of water deficiency, i. e. the state when the human organism does not receive enough water to ensure the proper interchange of microelements and minerals and function healthy. Dehydration, the ways to avoid it, and the possible effects of it are the topic of this paper. Water and Health To start with, however, it is necessary to consider the role that water plays for the human health. To put it simply, water is responsible for not only keeping a person healthy but for keeping the person alive as well. Given the data that an average human being consists of water for 50% to 75%, it is obvious that without water the very functioning of the human organism would be impossible (Grosvenor and Smolin, 2005). Moreover, water is essential for human life as far as it provides for a balance of the microelements and minerals in the human body. In other words, it is water that helps make some minerals less concentrated in a body; at the same time, it can bring the lacking minerals to the region of the organism where their concentration is weak. Functions of Water Needless to say, the functions of water in the human body are numerous. First of all, water is the element of body construction that facilitates the very process of living and proper functioning of the human being. Secondly, as far as the human organism consists of cells, water is the major building material for them. There are intracellular and extracellular fluids that deal with building cells and ensuring their proper interaction in the human organism; as well there is a notion of the interstitial fluid, which consists of the water from the blood and extracellular fluid (Grosvenor and Smolin, 2005). The functions of all these types of water in human organisms are focused on the process of osmosis, whose essence lies in the water passive movement across a membrane of every single cell in order to equalize the concentration of minerals in and out of cells. Finally, water serves as the body temperature regulator and a participant of chemical reactions in the organism. Issues from Lack of Water Further on, when an organism feels the need for water, the first signal to this is thirst. A human being feels thirst through the symptoms of dry mouth and weakness. The water needed is usually proportionate to the water lost, but the signals from the brain might be too late to manifest thirst and the amount a person drinks might be smaller than needed. In this case, if the water supply for the organism is absent at all, the state of dehydration comes