This prospective, single-arm interventional pilot study evaluated whether vitamin D supplementation alone improves iron status in adults with inflammatory bowel disease (IBD) who are in clinical remission and have concurrent vitamin D deficiency. Because vitamin D can suppress hepcidin-a key regulator that inhibits iron absorption-the investigators hypothesized that correcting vitamin D deficiency might improve iron parameters. Adult IBD patients (Crohn's disease or ulcerative colitis) in clinical remission with serum 25-hydroxyvitamin D \<20 ng/mL, ferritin \<40 µg/L, and no anemia received oral cholecalciferol (50,000 IU weekly for 8 weeks, followed by 2,000 IU daily) and were reassessed at 3 months. The primary outcome was the within-subject change in iron parameters (serum iron, ferritin, and transferrin saturation) from baseline to 3 months. The study also examined the change in 25(OH)D and explored differences by IBD subtype and biologic therapy use.