Total and free vitamin D status among apparently healthy adults living in Duhok Governorate.

Serum total 25-OHD is a main marker of vitamin D which represents the intake and sunlight exposure. Free form of 25-OHD, the small fraction not bound to a transporter protein has been incorporated as a new marker. This cross-sectional study aimed to evaluate the impact of several factors on total and free vitamin D levels in healthy subjects and to find out if the free form of vitamin D could be a better representative of the body's vitamin D status.