The frequency of taking vitamin D supplements was 27.0% in Iran in 2018. The frequency of taking of vitamin D supplements among vitamin D deficient group (serum vitamin D levels <19.99 ng/ml) was 43.6%. Lack of knowledge was the most important reason for not taking vitamin D supplement. Moreover, the serum vitamin D levels have increased in subjects aged 18-30 years old after the implementation of the vitamin D supplementary program.
