Water is quite trivial for people and so much so that we do not notice it and do not realize its importance for life. A person consists of almost 65% water, that is, more than half of the body weight is simply water. It is in water that all biochemical processes occur; it is water that contributes to the correct course of biochemical processes and it is water that contributes to the so-called optimum conditions for enzymes to function correctly. People, as a rule, do not experience problems in obtaining water in sufficient volume, and yet many of the patients experience a water deficiency in their body without even suspecting it. But the reader may have a question: “how is that? The body usually signals us about the lack of water through the feeling of thirst.” At first glance, all this seems correct. Let’s look at a number of values and what is behind them. Scientists have calculated that all water is distributed into the following areas: a) intracellular, b) intercellular, c) intracavitary. Intracellular – about 60%, intercellular – about 30%, intracavitary – about 10%. The body always strives to maintain the constancy of its internal environments and processes, while giving preference to the most important ones (the so-called law of hierarchy). The primacy (hierarchy) is traced both in the distribution of water and in the importance of the body’s organs. Intracavitary water (blood belongs to it) will be in 1st place in the hierarchy, intercellular – 2nd and intracellular – 3rd. Among the organs, the brain is of the greatest importance. If for some reason there is a water deficit in the body, then in order to maintain the constancy of intracavitary water, the body will begin to take it from the intercellular, and that in turn will begin to take it from the intracellular. And most often the body will take it from those cells that, as the body considers, are less important for the body as a whole. Therefore, most often the body removes water from the muscular and osseous-articular systems. Therefore, it is not surprising that with age, a person’s joints begin to suffer. Unfortunately, with age, the feeling of thirst, which signals a lack of water, decreases. Also, a lack of water can be masked by a feeling of hunger, so older people, instead of drinking water, begin to eat something. How to solve the problem of water deficiency? Scientists believe that to fully replenish water in the body, you need to drink at least 30 ml per 1 kg of body weight. That is, if a person’s body weight is 70 kg, then he needs about 2100 ml of water per day.