The method described in the paper is intended for quantitative determination of the true sugar content in the urine. The quantitative determination of sugar in the urine is carried out selectively in the strongly carbonated medium following preliminary removal of hindering substances. The method can be expressed stechiometrically, this permitting to obtain a reliable result concerning the blood sugar level, and meets all the clinical diagnosis requirements. The method can be used in any laboratory, being reliable and sufficiently sensitive.