Low vitamin D levels have also been associated with many chronic diseases, including diabetes mellitus, hypertension, cancer, and autoimmune diseases. This study aimedto examine the 25-hydroxy vitamin D (25OH-D) level studied Medical Biochemistry Laboratory of Afyon Health Sciences University between January and December2015 according to age, sex, and season. A total of 7291 individuals (5326 women and 1965 men) who applied to the Afyon Health Sciences University Medical Biochemistry Laboratory for the first time between January 1 and December 31, 2015, were included in the study. The 25OH-D level of the individuals included was retrospectivelyevaluated according to age, sex, and season. Results: It was observed that 61.7% of the measurements were done in summer and 39.3% in winter. The 25OH-D level wason an average 19.913.27 ng/mL in men and 14.9313.75 ng/mL in women, and an average of 16.4313.54 ng/mL in summer and 16.0214.21 ng/mL in winter. Althougha significant correlation was found between the 25OH-D level and sex, no statistically significant correlation was found with the season. When the 25OH-D level wasevaluated according to age decades, the lowest value was observed in the tenth decade, with an average of 13.1612.87 ng/mL, and the highest value was observed in thefirst decade, with an average of 31.6216.89 ng/mL. A statistically significant difference was found between decades. Located in the Aegean region, Afyonkarahisar issuitable for benefiting from the sun due to its latitude and atmospheric structure. Moreover, sun exposure during the day is low due to the lifestyle and clothing style. Forthis reason, the level of vitamin D synthesized in individuals is affected because ultraviolet-B radiation does not reach the skin. These findings suggest that both nutritionaland vitamin D supplements are important for the improvement in vitamin D deficiency in Afyonkarahisar province.