An apparatus for measuring change in sugar concentration in a fluid relative to a baseline concentration, the apparatus comprising: an optical energy source arranged to produce initial optical energy ; a first polarizer disposed such that the initial optical energy passes through the first polarizer so as to form polarized energy ; a second polarizer rotated relative to the first polarizer by a first rotational amount Θ and spaced a distance from the first polarizer to form a space for receiving at least a portion of an ear containing the fluid; a first optical detector ; and a second optical detector positioned proximal to said second polarizer ; wherein the first optical detector is arranged such that a first portion of the polarized energy traverses the space to the first optical detector ; wherein the second polarizer and the second optical energy detector are arranged such that a second portion of the polarized energy passes through the second polarizer to the second optical energy detector ; the apparatus further comprising at least one circuit coupled to said first optical detector and said second optical detector , said at least one circuit comprising: a compensating circuit arranged to either attenuate a first signal received from the first optical detector or boost a gain of a second signal received from the second optical detector to compensate for the loss of intensity attributable to the portion of polarized energy passing through the second polarizer and the effects of polarization due to the baseline concentration in the fluid; and a subtractor circuit coupled to the compensating circuit and arranged to produce a signal that is dependent on a difference between the first signal and the second signal . an optical energy source arranged to produce initial optical energy ; a first polarizer disposed such that the initial optical energy passes through the first polarizer so as to form polarized energy ; a second polarizer rotated relative to the first polarizer by a first rotational amount Θ and spaced a distance from the first polarizer to form a space for receiving at least a portion of an ear containing the fluid; a first optical detector ; and a second optical detector positioned proximal to said second polarizer ; wherein the first optical detector is arranged such that a first portion of the polarized energy traverses the space to the first optical detector ; wherein the second polarizer and the second optical energy detector are arranged such that a second portion of the polarized energy passes through the second polarizer to the second optical energy detector ; the apparatus further comprising at least one circuit coupled to said first optical detector and said second optical detector , said at least one circuit comprising: a compensating circuit arranged to either attenuate a first signal received from the first optical detector or boost a gain of a second signal received from the second optical detector to compensate for the loss of intensity attributable to the portion of polarized energy passing through the second polarizer and the effects of polarization due to the baseline concentration in the fluid; and a subtractor circuit coupled to the compensating circuit and arranged to produce a signal that is dependent on a difference between the first signal and the second signal . a compensating circuit arranged to either attenuate a first signal received from the first optical detector or boost a gain of a second signal received from the second optical detector to compensate for the loss of intensity attributable to the portion of polarized energy passing through the second polarizer and the effects of polarization due to the baseline concentration in the fluid; and a subtractor circuit coupled to the compensating circuit and arranged to produce a signal that is dependent on a difference between the first signal and the second signal . <EOS>