Ancient health care attached great importance to the cleaning of urine. Su Dongpo's Miscellaneous Notes on Health Care says, "Live long and urinate long". Urine is clean, indicating that human body's water and liquid metabolism is normal, and waste can be eliminated. How to keep urine clear? Drink plenty of water: drink 6 cups a day (250 ml each). In the case of exercise, high temperature and dry environment, the amount of drinking water should be increased. Drinking more water can dilute urine, reduce the stimulation of toxic substances in urine to the bladder, and have the effect of "flushing" the bladder. Don't hold your urine: Holding your urine will not only increase the residence time of the poison, but also increase the pressure in the bladder. If urine returns to the kidney, it will also induce chills, fever, backache, frequent urination and urgency. Fang thinks that "urination is unfavorable, and cold knees cause arthralgia", and points out the importance of timely urination. Don't urinate hard: let nature take its course and don't hold your breath hard. When a man reaches a certain age, he may have symptoms of prostatic hypertrophy. If necessary, he will draw blood to check the "prostate specific antigen". The weak advocate squatting or sitting to urinate, so that urine can be discharged slowly, so as not to consume too much and damage the kidneys.