High Dose Interval Vitamin D Supplementation in Patients With Inflammatory Bowel Disease Receiving Biologic Therapy

Inclusion Criteria: * Existing diagnosis of IBD, including Crohn disease, ulcerative colitis, and indeterminate colitis * Receiving treatment with Infliximab or Vedolizumab every 4-8 weeks * Age 5-25 years old, at study entry * Measured serum level of 25-OHD of less than 40 ng/mL in the last 4-8 weeks and no changes in vitamin D supplementation in the interim. Of note, 25-OHD levels are evaluated routinely as part of standard clinical care for IBD Exclusion Criteria: * History of any underlying kidney disease * History of preexisting liver disease * History of granulomatous disease * Inability to take oral vitamin D3 as a pill * History of hypercalcemia or hypercalciuria * Currently, or within the past 3 months, taking an anti-epileptic medication or Lasix