Abstract: A method for measuring the concentration of a compound in the blood of a part of a subject is provided. An invasive or non-invasive sample of blood may be used for this determination. Also provided is a device for measuring the concentration of a compound in the blood of a subject. The device comprises a source of electromagnetic radiation, a holder, a detector and a processing system.

Abstract: A method and apparatus for measuring Tot-Hb in a sample are provided. The method involves collecting absorbance measurements of a sample using a spectroscopic apparatus that includes a first primary calibration algorithm for one of Oxy-Hb, “Oxy-Hb plus Deoxy-Hb”, or “Total-Hb minus Met-Hb” and a second primary calibration algorithm for one or more than one of Met-Hb, Carboxy-Hb, or Sulf-Hb, or includes a third primary calibration algorithm obtained by adding terms of the first primary calibration algorithm and the second primary calibration algorithm together. Followed by predicting either a first value for one of Oxy-Hb, “Oxy-Hb plus Deoxy-Hb,” or “Total-Hb minus Met-Hb” and predicting second value for one or more than one of Met-Hb, Carboxy-Hb, or Sulf-Hb in the sample and adding the first and second value together, or predicting a value for Total-Hb.