A method and apparatus to assess sudomotor function to detect early stage peripheral distal neuropathy. The method sends a low voltage direct current of 1 to 5 volts between pairs of electrodes for a time of between 15 and 60 seconds, switches the current at the middle of the time and measures the peak and slope of the decreased conductance. The method can be used to assess skin blood flow and/or sweat gland density depending on the direction of the current.
