Adjunctive Treatment With Vitamin D3 in Patients With Active IBD

Inclusion Criteria: * Established diagnosis of CD, UC, or IBD-unspecified * Initiating anti-TNF therapy for IBD within 2 weeks of baseline/randomization * Other non-anti-TNF IBD medications must remain stable during the treatment period with the exception of tapering of corticosteroids. * Recent (within 6 months) objective evidence of active IBD on colonoscopy along with elevated inflammatory markers (C-reactive protein \>8 mg/L or fecal calprotectin \>150 mcg/g) * Current disease activity defined as a Harvey Bradshaw index \> 4 at baseline (week 0) for CD subjects or Simple Clinical Colitis Activity Index \> 2 at baseline (week 0) for UC subjects. * Fecal Calprotectin level \>150 mcg/g Exclusion Criteria: * Inability to provide informed consent or unwilling or unlikely to comply with the requirements of the study. * Female subjects who are pregnant, lactating, or intending to become pregnant during the study period * Known intolerance or hypersensitivity to oral vitamin D3 supplementation * Plasma 25(OH)D \> 60 ng/mL * Known celiac disease or subjects with a positive screen for celiac disease (elevated tissue transglutaminase antibodies) * Serum calcium \>11 mg/dL * History of hyperparathyroidism * History of renal calculi or chronic kidney disease * Initiation of anti-TNF treatment for extra-intestinal symptoms alone * Evidence of untreated infection (e.g. Clostridium difficile) * History of chronic pancreatitis * History of cystic fibrosis * History of gastric bypass * Presence of stoma or J-pouch