The present invention provides methods and apparatuses for determining a measure of a tissue state in an individual. Light emitted by tissue of the individual due to fluorescence of a chemical with the tissue detected. The invention can comprise measuring the fluorescence lifetime in either time-domain or frequency domain modes. The invention can also comprise a variety of models relating fluorescence to a measure of tissue state, for example, multivariate models can be developed that relate lifetime trends of one or more constituents to increasing propensity to diabetes and pre-diabetes. Other biologic information can be used in combination with the fluorescence properties to aid in the determination of a measure of tissue state.
