A non-invasive blood glucose concentration sensing system and method includes emitting light of a first color into an eye of the user and then emitting light of a second color into the eye of the user, or flashing blue light into the eye of the user. Neurophysiological brain activity and electrical responses of the eye of the user are sensed during and after emitting or flashing of the light into the eye of the user. In a processor, one or both of the sensed neurophysiological brain activity and the sensed electrical responses of the eye are correlated to the glucose concentration in the blood of the user.
