A method for optical measurements of desired parameters of the patient's blood is presented. A state of the blood flow cessation is provided within a measurement region and maintained during a predetermined time period. Measurement sessions are performed within this predetermined time period. Each measurement session includes at least two measurements with different wavelengths of incident light. Obtained measured data is representative of the time dependence of light response of the blood in the measurement region. The analyses of the measured data enables the determination of the desired blood parameters extracted from optical characteristics associated with the erythrocytes aggregation process during the state of the blood flow cessation.