A system and method for extracting a biological fluid from an organism and continuously monitoring its characteristics. The system comprises a tissue interface device (100) suitable for positioning on or about the surface of the biological membrane of the organism and a monitor and control unit (200) coupled to the tissue interface device (100). The tissue interface device (100) comprises a sensor (115) positioned in a flow path of the fluid for continuously sensing a characteristic of the biological fluid as it flows out from the one or more artificial openings formed in the biological membrane. The sensor (115) generates a sensor signal representative thereof. The monitor and control unit (200) electrically or optically reads the sensor (115) to obtain a measurement of a characteristic, such as concentration of a particular analyte, of the biological fluid on a continuous basis.