At 7 and 14 days after the screening colonoscopy patients will be called on the telephone by the clinical research nurse assigned to this study to follow-up and note 25(OH)D3 (calcifediol) toxicity, if any (note that toxicity has not been described except in the case of overdose). Signs specifically looked for will include: headache, increased urination, nausea, vomiting, abdominal pain, weakness, constipation, and anorexia. If present, patient will be advised to present immediately to the UIC GCRC for physical and serological evaluation.