A portable bioelectric impedance monitor for monitoring extracellular fluid levels includes a tetrapolar electrode array lead with four electrodes arranged sequentially and axially along the lead, and circuitry coupled with the at least four electrodes configured to measure bioelectric impedance extracellular fluid in a human subject at a frequency of less than 15 kHz. The electrodes are adhered to a human subject/patient on the patients torso or one of the patients limbs. One embodiment includes a Tetrapolar Analog Front End Patient Interface circuit configured to convert two electrode operation of a commercial Impedance Converter, Network Analyzer into a tetrapolar operation for excitation and impedance measurement of the human subject.
