A new method for monitoring the state of urine has been developed, which allows to determine the density ρm, osmolarity Os and the size of protein compounds Db in real time with high accuracy. Modernization of the mobile  refractometer design to implement this method to provide measurement of biological solution sample parameters with a single instrument. Providing ease of operation and maintenance, high accuracy of measurements, application  without pre-calibration of the scale after each switching on. The results of determination of density, osmolarity, size of protein compounds and total number of solid particles by measured refractive indices n at different wavelengths were compared with the results of measurements on other devices and confirmed the reliability of the developed method. The parameters of human urine, by which it is possible to establish kidney disease at an early stage with high  probability, were determined.