Under normal circumstances, the urine just discharged by the human body is relatively pure, without any bacteria as well as foreign body contamination. If urine is left to stand overnight and white precipitates appear, it is possible that the salts of urine, due to the evaporation of water, have reduced solubility, resulting in the precipitation of crystals, which is a normal process of urine dissolution with the formation of analysis out. It may also be due to the process of decomposition and metabolism of substances in the urine by bacteria that enter the urine after the urine has been sitting for a period of time, and these substances will precipitate into the urine and form white substances, which is generally caused by bacterial contamination. If the patient has no symptoms of discomfort when discharging urine and only white precipitation appears during overnight resting, there is generally no need for special concern. It is also possible that recent changes in diet structure, such as the intake of a high-fat diet as well as meat, can lead to high levels of salts and protein in the urine and the appearance of urine precipitation after resting. Patients with uncomfortable symptoms are advised to have a routine urine test, which can usually clarify the specific disease.