Vitamin D to Improve Nutrition Prior to Bariatric Surgery and Investigate the Relationship With Negative Outcomes

VISTA is looking to see if vitamin D supplements before bariatric surgery might improve vitamin D stores, which may help to prevent some complications like infections. Who can join this research study? * Approved to undergo bariatric surgery-Roux-en-Y Gastric Bypass or Vertical Sleeve Gastrectomy-at the Johns Hopkins Bayview Medical Center * 18 to 64 years of age * BMI of 35 to 49.9 kg/m2 * VitD insufficient or deficient prior to having surgery What will happen if a participant chooses to participate in this research study? * The participant will be randomly assigned (by chance) to receive either: * Standard care plus vitamin D supplements or * Standard care plus a placebo (contains no vitamin D) * Either would be provided at no cost to the participant * The investigators will ask the participant to complete a survey on the day of surgery regarding supplement use * The investigators will follow the participants medical record through the 12 month follow up clinic visit.