Method for providing custom calibration for near infrared instruments for measurement of blood glucose

A method is disclosed for easily and reliably custom calibrating near-infrared quantitative analysis instruments including obtaining a plurality of blood samples and blood glucose level measurements thereof at a predetermined time interval. These values are entered into the analysis instrument. Near-infrared optical measurements of the individual are simultaneously taken using the analysis instrument at another predetermined time interval. Calibration regression analysis is performed on the data to custom calibrate the analysis instrument which involves linearly interpolating the blood sample glucose measurements with the near-infrared optical recordings.