Isotonic urine (urine concentration and dilution function is reduced): CRF (chronic renal failure) early renal function is reduced while dilution function is normal, with the aggravation of the disease, the kidney dilution function is also impaired, so that the final urine osmolality is close to plasma, urine specific gravity is often fixed at 1.008-1.012, called isotonic urine. The osmotic pressure of urine is measured by the freezing point reduction method to reflect the concentration of solutes in urine. The osmolarity of isotonic urine is 250-400 mOsm/L. So, how is isotonic urine diagnosed? The following are diagnostic methods for isotonic urine: 1. Urine color: Normal urine is light yellow to yellowish brown. It is often affected by diet, sweating, etc. In addition, soy sauce, red wine, dark brown and other colors of urine can be seen. After excluding the influence of drugs, it is recommended to go to the hospital for further examination. 2, urine volume: in general, normal adults urinate O.8 to 2.0 liters a day and night (24 hours). However, water consumption, exercise, sweating and temperature can affect the volume of urine. 3, specific gravity: the specific gravity of normal people 24 hours urine in about 1.015. Often fluctuates between 1.010 and 1.025, due to the influence of diet, exercise, sweating, etc.. Random urine specific gravity fluctuation range of 1.005 ~ 1.030. 4, transparency: fresh urine clear and transparent without precipitation. After sitting for a period of time, flocculent precipitation can appear, especially in female urine. Urine is cloudy when it is discharged, often due to white blood cells, epithelial cells, mucus, microorganisms and other causes.