serum 25-hydroxyvitamin d levels in patients referred to clinical laboratories in various parts of mashhad- northeastern iran

introduction: vitamin d has an important role in maintaining human health. the main source of vitamin d production is skin exposure to sunlight. accordingly with the spread of apartment life culture, growth of industrial cities and the increase of air pollution; vitamin d deficiency and its implications is an important factor in the appearance of debilitating diseases in different age categories (especially for children, adults and elderly people).   materials and methods: a retrospective cross-sectional study based on an objective was conducted on 1,110 patients who were selected randomly. these patients have been referred to “center of education culture and research” laboratories (2 laboratories) and 8 specialized laboratories for vitamin d test in the city of mashhad. and after conducting the study, the collected data was analyzed using spss 13 software.   results: the prevalence of vitamin d deficiency in the population under study was 68.8%. vitamin d levels were significantly lower in males in comparison with females (p <0.05). and the statistical correlation between age and vitamin d deficiency was also significant (p <0.05). the results showed a significantly positive correlation between age and vitamin d deficiency (r = 0.187 and p = 0.000), consequently vitamin d deficiency in 40-59 age group was more prevalent.   conclusion: the prevalence of vitamin d deficiency in the residents of the city of mashhad is higher in men in comparison with women. and vitamin d deficiency has increased considerably in this city in comparison with the past years.