A method of non-invasively measuring the presence, absence, or
concentration of one or more analytes in a tissue of a subject includes
exposing at least a portion of a tissue of the subject to electromagnetic
radiation; obtaining a measurement of electromagnetic radiation from the
tissue; and determining the presence, absence, or concentration of one or
more analytes by determining a radiation signature of the electromagnetic
radiation; correlating the radiation signature of the electromagnetic
radiation with at least one of concentration, presence, and absence of
one or more analytes by utilizing a mathematic transformation such as a
transformation based on a 1.sup.st or higher derivative of the
measurement to determine the presence, absence, or concentration of one
or more analytes in the subject.