Lung adenocarcinoma in advanced stage drinking less water and sleeping all the time may be the manifestation of malignant disease or adverse drug reaction, or it may be caused by complication of hyponatremia. 1. Malignant disease: it is a kind of complex metabolic clinical syndrome, secondary to consumptive diseases such as lung adenocarcinoma, gastric cancer, breast cancer, or AIDS, sepsis and other diseases. Because of the metabolic disorder in the advanced stage of lung adenocarcinoma, multiple organs may have dysfunction, so there will be symptoms such as fatigue, drowsiness, loss of appetite, which may be manifested as drinking less water and sleeping all the time. 2. Adverse drug reaction: because lung adenocarcinoma needs to cooperate with doctor to carry out chemotherapy and apply bevacizumab and other drugs according to doctor’s instruction in advanced stage, so drinking less water and sleeping all the time in advanced stage may be the manifestation of adverse drug reaction. 3. Hyponatremia: this disease belongs to water-salt balance disorder, because lung adenocarcinoma will lead to antidiuretic hormone secretion disorder, which will cause hyponatremia, so the patients will have symptoms such as drowsiness, fatigue, and drinking less water. There are many reasons leading to the late stage of lung adenocarcinoma drinking less water and sleeping all the time, and it is necessary to go to the hospital for consultation to clarify the specific reasons. For medication, please strictly follow the doctor’s prescription and do not use medication by yourself.