The 24-hour urine output of 4000mL may be related to uremia, drug factors, diabetes mellitus and other causes. 1. Uremia: The decrease in secretion of antidiuretic hormone or the lack of renal response to antidiuretic hormone will lead to uremia, causing polyuria phenomenon, which leads to the symptom of 24-hour urine output of 4000ml. 2. Drug factors: the use of dehydration, such as mannitol injection and oral diuretics, such as furosemide tablets, hydrochlorothiazide tablets, etc. will cause an increase in urine output, resulting in a 24-hour urine output of 4000 ml of symptoms. 3. Diabetes mellitus: diabetic patients with high blood sugar are easily thirsty and drink a lot of water. Excess sugar can only be excreted in the urine. Glucose in the urine leads to an increase in osmolality and a decrease in water reabsorption in the renal tubules leading to polyuria, resulting in the symptom of a 24-hour urine output of 4000ml. It is recommended that patients with markedly increased urine output go to the hospital in time, and under the guidance of the doctor to clarify the cause of the disease and then correctly treat it, so as not to delay the condition.