Urine specific gravity is reduced then the possible causes: First, more water consumption causes more body fluid, and the water discharged through the kidney filtration will increase. The relative content of creatinine and other metabolites in the urine is reduced, so the specific gravity is slightly lower, which is equivalent to the specific gravity of water. This condition is usually not accompanied by any abnormal urination or abnormal kidney function, and only requires appropriate control of water consumption. Second, when there is chronic glomerulonephritis or renal insufficiency, the metabolic wastes in the body cannot be completely filtered out of the body through the kidneys. But the amount of water excreted remains unchanged, so it shows a decrease in specific gravity. At the same time, it can be accompanied by a mild increase in serum urea nitrogen and creatinine, or accompanied by facial or limb edema and other changes, which requires a kidney function test to further confirm the diagnosis. Third, when suffering from uremia, the patient can eliminate a large amount of water, the daily urine volume can exceed 2500ml or more than 5000ml in severe cases. the majority of the urine excreted is water, and the relative content of metabolic waste is low, so the specific gravity is low.