Method and apparatus for spectroscopic tissue analyte measurement

Methods and systems for calculating body fluid metrics are provided. In accordance with an exemplary embodiment of the present technique, there is provided a method for calculating body fluid metrics by acquiring an absorbance spectrum of a subject's tissue over a range of near-infrared light, performing a multi-linear regression of the absorbance spectrum of the subject's tissue in relation to absorbance spectra of tissue constituents, and calculating body fluid metrics based on the results of the multi-linear regression. A system is provided having a sensor for emitting the light into the subject's tissue and detecting reflected, scattered, or transmitted light, a spectrometer for processing the detected light and generating the absorbance spectrum of the subject's tissue, memory for storing absorbance spectra of the tissue constituents and a multi-linear regression model, and a processor for performing the multi-linear regression and calculating the body fluid metrics.