Etiology of serum vitamin B(12) elevation 1 month after bariatric surgery: A case-control study based on China population

Few studies have reported an increase in vitamin B(12) (VitB(12)) levels after bariatric surgery. This study reports the phenomenon and adverse reactions of serum VitB(12) elevation 1 month after surgery and explores the possible etiologies. Retrospective analysis was performed on VitB(12) data for 112 patients from January 2018 to October 2019. Then, 87 patients were included between November 2019 and August 2020. They were divided into 2 groups according to the level of VitB(12) after surgery, and the demographic and clinical data were analyzed. Then, LASSO regression model analysis and multiple logistic regression analysis were performed to explore the risk factors for VitB(12) elevation after surgery. Retrospective data showed that the VitB(12) level was significantly increased 1 month after surgery. Comparison of data between the 2 groups found that more patients also had diabetes in the nonelevated group. The postoperative folic acid and VitB(12) levels of the elevated group were significantly higher than those of the nonelevated group. More patients had concurrent constipation in the elevated group than in the nonelevated group. Two meaningful variables in LASSO regression analysis were incorporated into the multivariate logistic regression analysis, and constipation was found to be an independent risk factor for the increase in VitB(12) after surgery. Of the 199 patients in this study, 111 patients had elevated VitB(12) levels after surgery. Among them, 7 patients had peripheral nerve symptoms. Constipation is an independent risk factor for increased VitB(12) levels after surgery. High levels of VitB(12) may cause some peripheral nerve symptoms. Therefore, it is necessary to pay attention to patients with postoperative constipation, monitor their VitB(12) level as soon as possible, and take measures to improve constipation to avoid some adverse reactions caused by elevated VitB(12) levels.