Most of the yellow urine caused by staying up late is due to the concentrated state of urine. Sitting up late or not drinking too little water in the process of staying up late can cause the urine to be concentrated, resulting in excessive water loss in the urine while the concentration of urine pigment remains unchanged, resulting in yellow urine. Usually there are no symptoms of urinary tract irritation, no frequent urination, no urgency, no painful urination, etc. Appropriate hydration can restore the color of urine to normal. Under normal circumstances, patients rest at night, the body is in a low metabolic state, but staying up late will lead to increased body consumption, evaporation of water through the respiratory tract, evaporation of water through the skin heat will be too much, there will be a relative lack of water in the body, coupled with staying up late because of smoking or not drinking water can lead to the concentration of urine and the phenomenon of yellow urine.