Investigation of 25-hydroxy vitamin D deficiency prevelance in healthy adults aged 18-65 years in Istanbul, Türkiye

The prevalence of vitamin D deficiency (below 20 ng/mL) in healthy adults aged 18-65 years in Istanbul was 57.2%. That prevalence varied across seasons and months, indicating that sunlight was not used sufficiently. Vitamin D deficiency in Istanbul presents a major problem that needs to be remedied.