The invention disclosed herein relates to a biological fluid constituent sampling and concentration measurement device, said device comprising: at least one skin-piercing member comprising a biological fluid access opening an electrochemical cell for measuring the concentration of analyte within the biological fluid, wherein the electrochemical cell comprises two spaced-apart electrodes defining a reaction chamber, wherein a first of the electrodes is on the same side of the reaction chamber as the skin-piercing member and the second of the electrodes is a porous electrode on the other side of the reaction chamber and a constituent transfer medium comprising a hydrophilic material in fluid communication with the at least one skin-piercing member and with the reaction chamber.
