Systems and methods are disclosed for non-invasively measuring blood glucose levels in a biological sample based on spectral data. This includes at least one light source configured to strike a target area of a sample, at least one light detector positioned to receive light from the at least one light source and to generate an output signal, having a time dependent current, which is indicative of the power of light detected, a processor configured to receive the output signal from the at least one light detector based on the received output signal, calculate the attenuance attributable to blood in a sample present in the target area with a ratio factor, eliminate effect of uncertainty caused by temperature dependent detector response of the at least one light detector, and then determine a blood glucose level with a sample present in target area based on the calculated attenuance with the processor.
