1. A method for measuring a blood analyte concentration, comprising the steps of: obtaining energy absorption measurement data through a body part of an individual; calculating a plurality of indicator variables from said energy absorption measurement data; determining which indicator variable from said plurality of indicator variables has the highest correlation to blood glucose level; allocating a first optical term based on said indicator variable with said highest correlation to blood glucose level to form a regression analysis equation; and calculating an estimated value of said blood analyte concentration using said regression analysis equation.