If the color of urine turns red after the human body has discharged it for a period of time, it is mainly due to the crystallization of soluble components in the urine, resulting in a change in color appearance, and there is no need to worry if the patient has no obvious symptoms of discomfort. If the patient’s urine is left for a longer period of time and becomes red, it is mainly due to the decomposition of bacteria in the environment mixed with the urine and the redox reaction, resulting in a red-like change in the color of the urine, which does not require special treatment. Therefore, if a patient has symptoms of discomfort after urination, a routine examination should be performed to clarify whether there is a change in the composition of the urine, commonly due to hemolytic diseases of the liver and gallbladder or the recent use of certain drugs, such as the anti-tuberculosis drug rifampin, which can lead to red changes in the urine after discharge. In other cases, patients who have recently taken B vitamins orally may have red urine after the urine has been discharged for a period of time, and the components of the urine may crystallize and cause red changes. If you have symptoms of urinary discomfort or other discomfort, you should check the urine routine to clarify the specific changes in the composition of the urine.