A glucose sensor measures glucose molecules in vivo through use of NDIR in which scattering noise is reduced and Absorption Interference Noise (AIN) is suppressed with a reflection technique. Electronics are used to provide an output of glucose concentration glucose in a liquid sampling matrix after it has been determined that a calibration curve is valid after signal processing is used to obtain average ratio values for reflected signal/reference channels and interference/reference channel obtained after a pulsed beam from signal, interference and reference sources is directed at an inclined angle to a normal of a spot of the liquid sampling matrix. The signal, interference and reference sources are each pulsed at a preselected frequency of at least N Hz which is sufficiently fast so that a given molecule of glucose or interfering molecule will not pass in and out of the liquid sampling matrix within the preselected frequency.
