Sodium is an essential mineral nutrient for human body. Most of sodium in the body exists in blood and extracellular fluid, which is closely related to body fluid balance and other physiological functions. Sodium ion (hereinafter referred to as sodium) is the most abundant positive ion in extracellular fluid, which helps to maintain osmotic pressure in vivo and assist the normal operation of nerves, heart, muscles and various physiological functions. There is a close relationship between the metabolism and balance of sodium and water in the body, which has a considerable impact on blood pressure. Sodium is a common ionic component in various body fluids. Sodium in the body is mainly excreted through urine made by the kidneys, but a considerable amount of sodium can also be excreted when sweating. The regulation of sodium in the body is closely related to the regulation of water. The hypothalamus can secrete antidiuretic hormone, which acts on the kidney to reduce the exclusion of water, thus regulating the water-sodium ratio in the body. The sodium content in human body is 105g, in which the bone surface accounts for 30% of the total content. The normal concentration of blood sodium is 3. 15-3.4g per liter of blood. The daily sodium loss is about 1 15 mg, of which 23 mg is excreted through urine and excrement, and 46-92 mg is lost through epidermis.