Fig. 1. Prevalence of vitamin D deficiency (<20 ng/mL), insufficiency (20-29.9 ng/mL), and sufficiency (≥30 ng/mL) among the study population. (A) By sex. (B) By age. (C) By month. (D) By season. Season was defined as spring (Mar-May), summer (Jun-Aug), fall (Sep-Nov), and winter (Dec-Feb). (E) By region groups. The urban area includes Seoul, Busan, Daegu, Incheon, Gwangju, Daejeon, Ulsan, and Gyeonggi-do. The rural area includes Gangwon-do, Chungcheongbuk-do, Chungcheongnam-do, Jeollabuk-do, Jeollanam-do, Gyeongsangbuk-do, Gyeongsangnam-do, and Jeju-do.Abbreviation: 25OHD, 25-hyrdoxyvitamin D. Fig. 1. Prevalence of vitamin D deficiency (<20 ng/mL), insufficiency (20-29.9 ng/mL), and sufficiency (≥30 ng/mL) among the study population. (A) By sex. (B) By age. (C) By month. (D) By season. Season was defined as spring (Mar-May), summer (Jun-Aug), fall (Sep-Nov), and winter (Dec-Feb). (E) By region groups. The urban area includes Seoul, Busan, Daegu, Incheon,. . . Lab Med Online. 2016 Apr;6(2):70-78. http://dx.doi.org/10.3343/lmo.2016.6.2.70