Water and inorganic salts (electrolytes) are important components of the organism and of body fluids. Body fluids are the internal environment for cellular life activities, and their constant volume, osmotic pressure, pH and appropriate concentration of various ions play an important role in ensuring the normal metabolism of cells. For example, hypotonic dehydration is the simultaneous deficiency of water and sodium, but the deficiency of water is less than the loss of sodium. This condition is an imbalance in the metabolism of water and inorganic salts. The main causes are: continuous loss of gastrointestinal digestive juices, such as repeated vomiting, long-term gastrointestinal tract attraction or chronic intestinal obstruction, resulting in the loss of sodium with a large amount of digestive juices; chronic oozing of large trauma; excessive renal excretion of water and sodium, such as the application of sodium-removing diuretics (clothianidin, diuretic acid, etc.), without attention to replenish the appropriate amount of sodium, resulting in the body is relatively more sodium deficiency than water deficiency. Isotonic dehydration is also called acute or mixed dehydration. Since water and sodium are lost in proportion, the serum sodium remains in the normal range and the osmolarity of the extracellular fluid can also remain normal. However, isotonic dehydration can cause a rapid decrease in the amount of extracellular fluid (including circulating blood volume). Tests for impaired water and salt metabolism include: 1. sucrose water hemolysis test. 2.Basal metabolism. 3.Blood electrolyte test. 4.Sweat electrolyte examination.