Whether low urine osmolality is dangerous or not is related to the cause, if it is caused by physiological factors such as drinking a lot of water, there is generally no danger, if it is caused by a variety of kidney diseases such as renal failure, there is a certain degree of danger, if it is caused by the disease, it is necessary to consult a doctor in time for appropriate treatment. Urine osmolality is the amount of all solutes in the urine excreted by the kidneys, including electrolytes, sugars, proteins, urea, etc. The result of urine osmolality test can reflect the concentration function of the kidneys. Decreased urine osmolality may be caused by physiological factors, such as drinking a lot of water to dilute the urine, which usually does not lead to danger, and can be restored to normal by controlling the amount of water consumption appropriately. Part of the decrease in urine osmolality is related to kidney diseases, including chronic pyelonephritis, polycystic kidney, uremia, chronic renal failure, acute tubular dysfunction, urinary tract obstructive nephropathy, primary glomerulopathy, etc. When the concentration function of the kidney is seriously impaired by the disease, the decrease in urine osmolality will occur. If the disease-induced lowering of urine osmolality fails to diagnose and treat the primary disease in a timely manner, it may progress to severe renal dysfunction and failure, which may lead to electrolyte disorders and other serious consequences. People with decreased urine osmolality are advised to seek prompt medical attention to identify the cause of the disease and follow the doctor’s instructions.