A method determines the concentration of a substance in a subjects blood. The method includes measuring an interaction of at least one light beam with a portion of the subjects body. The method further includes calculating a value of an optically-measured parameter indicative of the interaction of the at least one light beam with the substance in the portion of the subjects body. The method further includes measuring values of one or more temperature-indicative parameters corresponding to a temperature of the portion of the subjects body. The method further includes accessing an empirical correlation of the optically-measured parameter and the one or more temperature-indicative parameters to concentrations of the substance in blood. The method further includes obtaining a concentration of the substance in the subjects blood using the empirical correlation. The concentration corresponds to the value of the optically-measured parameter and the values of the one or more temperature-indicative parameters.
