Biliopancreatic diversion (BPD) is a form of bariatric surgery that produces substantial and sustained weight loss, improved co-morbidities, and a higher quality of life. However, it does have associated sequelae such as vitamin D deficiency. With limited published data, a comprehensive review of vitamin D levels in BPD patients was warranted. All available 25-hydroxyvitamin D (25-OH-D) levels were assessed from 219 BPD patients. The dates of 25-OH-D levels were compared to each individual patent's surgery date. Data was analyzed according to patient sex, ethnicity, age, and time from surgery. The majority (72.3%) of 25-OH-D levels (n = 607) in BPD patients were insufficient (a parts per thousand currency sign30 ng/ml), and 46.8% were deficient (a parts per thousand currency sign20 ng/ml). Statistical analysis revealed that 25-OH-D levels decrease over time with BPD patients (n = 0.0468), and no significant relationship exists with patient sex, ethnicity, or age. This study gives evidence that vitamin D deficiency and insufficiency is prevalent in BPD patients. Despite excess weight loss and oral vitamin D supplementation, the data shows that vitamin D levels continue to decrease over time in BPD patients. Since the current method of vitamin D supplementation is not producing ideal results, other protocol needs to be developed.