AbstractLower bone mineral density (BMD) constitutes a common issue in inflammatory bowel disease (IBD). Studies often explore the association between BMD and folic acid level. The presented study aimed to evaluate the impact of MTHFR gene polymorphism and folic acid levels on BMD in patients with IBDs: Crohn’s disease (CD) and ulcerative colitis (UC). The study group comprised IBD patients and a healthy control group. BMD, T-score, and Z-score of the lumbar spine (L1-L4) and femoral neck (FN) were assessed using dual-energy X-ray absorptiometry. Folic acid level was determined using direct chemiluminescence, and the MTHFR 677C > T (rs1801133) and 1298A > C (rs1801131) genotyping were performed by HRMA. Our study found no significant differences in the folic acid levels between the groups. Patients with CD and UC presented a lower BMD, T-score, and Z-score of the FN and L1-L4 than the CG. UC patients who were homozygotes AA in loci c.1298A>C presented lower than controls lumbar spine L1-L4 BMD and T-score values. Regarding MTHFR 677 polymorphism, we found that IBD patients carrying CC genotype demonstrated lower than controls femoral neck Z-score, lumbar spine L1-L4 BMD, T-score and Z-score. MTHFR polymorphisms were found to have no impact on folic acid concentrations. IBD patients presented a higher risk of low BMD than the healthy controls, regardless of MTHFR 677 and 1298 genotypes. However, MTHFR polymorphism may influence on bone in IBD patients. Nevertheless, it appears essential to conduct further studies.