Sudden decrease in urine output, need to go to the hospital for further examination to clarify the possible causes: 1, acute renal failure. It is common in pre-renal, or renal factors, the emergence of insufficient renal perfusion and lead to a sudden decline in filtration rate, or complications of glomerulonephritis, acute nephritis, etc., which leads to a decrease in glomerular filtration rate, resulting in a decrease in urine output. It is necessary to count the urine volume in 24 hours and perform renal function tests to further assess the degree of renal damage; 2. Post-renal obstruction, bilateral ureteral stones, prostatic hyperplasia, urethral stones and other diseases, resulting in urinary tract obstruction, the urine produced by the kidneys can not be discharged from the body, and is retained in the body, which will produce a sharp decrease in the volume of urine. And it is mostly accompanied by pain at the site of obstruction, such as low back pain, abdominal pain, and pain in the urethra. Further urinary system ultrasound is needed for examination; 3, dehydration, insufficient water. If the summer heat, excessive water loss or heat stroke, or drinking less water and lead to reduced renal filtration, urine output is reduced, at this time the whole day 24-hour urine volume is generally not less than 400 ml. need to drink more water, supplement body fluids, observe whether the urine volume increases. However, if you drink more water, replenish the body fluids, etc., the urine volume does not increase, then you need to go to the hospital in time to check.