If the urine volume is low and yellow, the possible causes are: 1. Less water, more sweating or more loss of body fluids, such as diarrhea, vomiting, etc., will result in concentrated urine, which will reduce the urine volume and be accompanied by a yellowish color. The urine volume can return to normal after proper hydration or rehydration.2. If there is a urinary tract infection, there can be a deepening of the urine color, accompanied by a decrease in urine volume, and accompanied by an increase in the frequency of urination or with abnormal urination, urinary urgency, painful urination or burning discomfort in the urethra. It is necessary to carry out routine urine examination and urine culture examination to further confirm the diagnosis.3. If there are metabolic abnormalities, yellow urine color can appear. If jaundice is present, it can cause the bilirubin level in the urine to rise, resulting in yellow urine. If there are other irritants in the urinary tract, such as bladder stones, ureteral stones, etc., there can be a decrease in urine volume, but an increase in the frequency of urination, accompanied by cloudy and yellow urine color. It may also be accompanied by pain in the area where the stone is located, such as back and abdominal pain. Ultrasound examination of the urinary system is required to further confirm the diagnosis.