Na<sup>+</sup>/K<sup>+</sup> Ratio in Blood Serum as a Criterion of Human Functional State

The article discusses the physiological significance of the Na+/K+ ratio in blood serum as a criterion of a person’s functional state. Normally, in an adult, the ratio is 32.2 ± 0.5, it increases in a healthy person under the influence of extreme factors (space flight (cosmonauts, astronauts), long-term strict bedrest, etc.), with Covid-19 disease, and some orphan diseases in children. The issue of Na+/K+ in blood serum is being discussed, but not between the K+-rich cell and the Na+-dominated extracellular environment. The Na+/K+ ratio in blood serum is considered as an important parameter of a person’s physiological state and, depending on the numerical value, as an indicator of the functional state from normal to overload, severe complications to the prognosis of death.