Decreased urine output is usually caused by physiological and pathological factors. The most common physiological factor is to drink too little water. When you drink too little water, the blood flow to the kidneys decreases, resulting in a decrease in urine output. If there is a lot of sweating or diarrhea, water flows out from the body surface and digestive tract, and less water passes through the kidneys, so the urine volume will also decrease, this is a physiological factor. Pathological factors are usually caused by kidney diseases themselves, such as renal insufficiency, renal failure, or even uremia, where the kidney function loses its compensatory role and water cannot be metabolized out of the body from the kidneys, so it accumulates in the tissue interstices and the urine volume decreases. When there is a decrease in urine volume, it is important to check the urine routine as well as kidney function tests to see and rule out organic lesions.