The modern trend in development of non-invasive glucometers evidently shifts from giving preference to simple technical solutions in to the field of Hi-Tech, from prevalent use of electro- and thermomeasuring methods to complicated optical technologies even up to Raman spectroscopy. In the same time the potentialities of electric impedance spectroscopy are not yet exhausted and demonstrate good clinical results. The work fulfilled by us is the following: considered are the physiological mechanisms of relationship of the magnitude of blood plasma and interstitial fluid osmolarity conditioned by glycaemia with transmembrane movement of water between blood, intra- and extracellular water compartments of organism.