Background and objectives: Vitamin D is an essential vitamin that plays a key role in maintaining physiological calcium balance, and is also a pivotal element in the formation of bone structure. Vitamin D deficiency is associated with a wide array of clinical symptoms. Vitamin and mineral deficiencies are quite common prior to and after bariatric surgery, and therefore we have evaluated the effects of two different cholecalciferol supplementation regimes on serum calcium, 25(OH) cholecalciferol, and parathyroid hormone (PTH). Materials and Methods: In this retrospective matched cohort study, two different cholecalciferol supplementation regimes were compared. Group A consisted of 50 patients who had 1000 mg calcium and 800 IU cholecalciferol. In Group B, 50 patients had 1000 mg calcium and 800 IU cholecalciferol with an additional 1 mL liquid cholecalciferol (50,000 IU) monthly. The primary outcome was the effects on blood serum levels of calcium, 25(OH) cholecalciferol, and PTH. Results: In group A and group B, there were significant increases in 25(OH) cholecalciferol, with a higher delta in favor of group B (for all three p < 0.001). A decrease was seen in PTH (p < 0.001), and no differences were measured in calcium levels in both groups. Conclusion: Our study suggests that an additional 1 mL cholecalciferol (50,000 IU) monthly can result in less biochemically 25(OH) cholecalciferol deficient patients after bariatric surgery. No effects were seen on the calcium balance. However, larger randomized clinical trials need to be done to assess the effects on clinical outcomes like bone health and fracture risk.