Whether or not a urine specific gravity of 1.005 is serious depends mainly on the cause of the decrease. If it is caused by physiological reasons, such as drinking a lot of water, reduce the amount of water intake can be, usually not serious; if it is caused by pathological reasons, such as renal failure, if not standardized and timely treatment, usually more serious. Urine specific gravity is the ratio of the weight of urine to the weight of the same volume of pure water at 4℃, which is an indicator of the concentration of solutes in urine. The reference value of urine specific gravity for adults is 1.015~1.025, so when the urine specific gravity is 1.005, it suggests that the urine specific gravity is reduced. It can be seen in physiological causes and pathologic causes. 1. Physiological reasons: if the patient drinks a lot of water before the test, it may make the patient’s urine specific gravity is low, at this time does not need to be treated, the patient only needs to control the amount of water consumption, this situation is usually not serious. 2. Pathological reasons: low urine specific gravity indicates that patients with renal tubular concentration and dilution function is impaired, can be seen in renal failure, etc., if not standardized and timely treatment, usually more serious. Patients with low urine specific gravity may also have other reasons, it is recommended that patients go to the regular hospital in time, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.