The human body urine after leaving the body if the rest time is longer, will gradually become dark yellow, this is mainly due to the environment of the bacteria, will break down the metabolism of urine salts and proteins, so as to form the color appearance of the change. Urine placed for a long time, the color of urine will gradually deepen, and ultimately will form a deep yellow color appearance, so if the patient needs to check the routine urine, urine specimens are recommended in the early morning hours for the retention of mid-range urine, urine specimens should be retained in time to send the test, do not place too long, the environment in the bacterial will inevitably enter the urine, the separation of the urine due to bacterial decomposition and metabolism, the urine The specific composition of the urine will be chemically altered, and once the composition is changed during the examination, the results will be distorted, so the urine should not be left too long.