In this study, the investigators will look for a correlation between the results of conventional blood test for detection of vitamin D levels in the blood and the results of measurements of spectral examinations that will be performed on various locations on the upper body of the subject. These measurements will take place in Hillel Yaffe Medical Center as the subject arrives to the Endocrinolgy department for the blood test. Visible lighy spectrometer (manufactured by Ocean Optics, USB 2000 model), connected to a optical fiber (manufactured by Ocean Optics, diameter 1 mm) will be used. The measurement will use a light soure (Fiberoptics Technology lnc. company. Model SOL-R150)Connected also to an optical fiber. Both ends of the fiber will be positioned on the upper body of the patient one of two configurations: for areas withe greater thickness, e.g. the forearm, the fibers would be placed next to each other on the same side of the limb to measure the return of the light, and in areas with smaller tissue thickness, e.g. finger tip, the fibers will be placed to bothe sides of an organ and record light transmission through the target.