Vitamin B12 toxicity secondary to post-bariatric supplementation: a case report on presentation and literature review

Introduction: Bariatric surgery leads to nutritional alterations, particularly affecting micronutrient levels. Vitamin B12 plays essential roles in neurological function and hematopoiesis. Postoperative changes in gastrointestinal anatomy disrupt B12 absorption, often necessitating supplementation. However, excessive supplementation may result in supraphysiological levels, with potential adverse effects. This report explores such a scenario to raise awareness about the need for balanced vitamin B12 management. Case Presentation: A 43-year-old male with obstructive sleep apnea underwent laparoscopic sleeve gastrectomy with an initial body mass index (BMI) of 38. Postoperative recovery was uneventful. He was prescribed multivitamins, vitamin D, and vitamin B complex. By the third month, he achieved a BMI of 25 but reported peripheral extremity weakness and numbness. Lab tests showed a vitamin B12 level of 1300 pg/mL (picograms per milliliter). Supplementation was halted, and after 1 month, symptoms resolved, and levels normalized to 617 pg/mL. The patient resumed normal activity and was advised regular B12 monitoring. Discussion: Vitamin B12 absorption is dependent on intrinsic factor and intact gastrointestinal anatomy. Bariatric surgeries alter this physiology, increasing the risk for both deficiency and excessive supplementation. Current literature highlights that while Roux-en-Y gastric bypass patients often develop deficiencies, Vertical sleeve gastrectomy patients may inadvertently accumulate B12 due to altered absorption patterns. Supraphysiological B12 levels may lead to oxidative stress and obscure other deficiencies. This case supports the necessity of tailored supplementation regimens and ongoing monitoring. Conclusion: This report underscores the importance of vigilant vitamin B12 monitoring in post-bariatric patients. Individualized supplementation plans and routine biochemical assessments are crucial to prevent both deficiency and toxicity. Further studies should investigate the long-term effects of high B12 levels in this population.