SummaryBackgroundsVitamin D is an important immune modulator in chronic liver diseases. The study aims to investigate the relationship between vitamin D and hepatitis B virus replication.MethodsThis was a prospective study. Hepatitis B virus (HBV) carriers were enrolled from May to Oct 2014 in Taipei Tzu Chi Hospital. All have positive hepatitis B surface antigen (HBsAg) for more than 6 months. Serum alanine aminotransferase (ALT), quantitative HBsAg (qHBsAg), HBV DNA and 25(OH)D3 were measured in each participant.Results204 patients (male 103; mean age 47.86 ± 10.22 years) with chronic HBV infection (94.12% HBeAg‐negative) were enrolled. Of them, 13 (6.4%) had severe deficiency (25(OH)D3 < 10 ng/mL), 176 (86.3%) insufficiency (25(OH)D3 ≥ 10 and < 30 ng/mL) and 15 (7.4%) adequate (25(OH)D3 ≧ 30 ng/mL) vitamin D levels. In the regard of age and sex, there was no difference in vitamin D levels. Using linear regression analysis, there was no correlation between serum vitamin D and HBV DNA/qHBsAg levels. While serum vitamin D levels were categorized by quartiles, there was no association between vitamin D levels and HBV DNA/qHBsAg levels using univariate and multivariate analyses.ConclusionsIn this study, 92.6% of patients with chronic HBV infection have inadequate vitamin D levels. Serum vitamin D levels do not correlate with the markers of HBV replication including serum HBV DNA and qHBsAg levels.Copyright © 2017, The Gastroenterological Society of Taiwan, The Digestive Endoscopy Society of Taiwan and Taiwan Association for the Study of the Liver.