Abstract: The present invention allows for non-invasive monitoring of the blood sugar levels in diabetic patients. At least one heat and waterproof applicator is applied to the skin surface by a dosage pressure. Temporal dynamics of physiological parameters of the local tissue region are measured under the applicator. Temporal dynamics of climatic parameters of the environment are measured simultaneously or before the beginning of measurement of physiological parameters in the monitoring mode. Further, enthalpy of tissue is calculated with account for the influence of climatic parameters. Magnitude of thermal effect of metabolism of the local area of living tissue is calculated on the basic thermodynamics equation, connecting enthalpy of tissue with variables of thermodynamic state. Relative changes in the level of glucose are calculated in blood, proportional to the value of the thermal metabolism of the local area of living tissue.