Some patients with lung cancer may develop hyponatremia due to the development of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), a very important hormone secreted by the hypothalamus in the body, which acts on the renal tubules of the kidneys to retain water in the body. If antidiuretic hormone is deficient, it can cause uremia, and a large amount of water will be lost from the urine, causing excessive drinking and urination. However, its secretion is also influenced by the osmotic pressure in the body, and if one is thirsty and does not drink water, the antidiuretic hormone is stimulated, allowing water to be retained in the body. Increased secretion of antidiuretic hormone may occur in the case of lung cancer. In addition, the effect may be enhanced, causing a large amount of water to be retained in the body, which dilutes the sodium in the body, thus creating dilutional hyponatremia, and the patient may suffer from severe hyponatremia. In addition, when lung cancer occurs or when hyponatremia occurs, it is important to conduct appropriate tests to analyze whether hyponatremia is combined with lung cancer. If hyponatremia occurs in lung cancer, the most critical treatment is of course to treat the lung cancer itself. At the same time, the method for hyponatremia is to restrict the amount of drinking water, not to drink too much, and to supplement sodium to help correct the hyponatremia caused by lung cancer. After active treatment of lung cancer and water restriction and sodium supplementation, the hyponatremia caused by lung cancer can be corrected. After lung cancer treatment, regular observation of whether the lung cancer has improved, whether it has been completely cured, and whether the disease has not recurred can also be helped by blood sodium monitoring.