Hyponatremia is also known as hyponatremia, low salt syndrome, etc. It is a more serious disorder of water and electrolyte metabolism, mainly due to insufficient sodium in the body or excessive water in the body, resulting in sodium deficiency or dilutional hyponatremia. It is also related to abnormal secretion of antidiuretic hormone (ADH), which produces dilutional hyponatremia. This symptom refers to a pathological state caused by a decrease in the total sodium content in the body. The total exchangeable sodium in the human body is 40-45mmol/kg. Low salt syndrome is often accompanied by hyponatremia, but there are also people whose serum sodium is not low. On the contrary, although most low sodium syndromes are accompanied by a decrease in the total sodium content in the body, there are also normal or increased ones. Clinically, serum sodium is measured rather than the total sodium content in the body. Low salt syndrome refers to a decrease in the total sodium content in the body, which is not strictly equivalent to low sodium syndrome.