Background: Advances in bariatric surgery have brought about a paradigm shift in the management of obesity, with benefits extending beyond weight loss. However, nutritional deficiencies are an inherent problem in the postoperative period and often require lifelong supplementation. Vitamin B12, also referred to as cobalamin, is one of the most common micronutrient deficiencies affecting this population. This review explores the pathophysiology of cobalamin deficiency in patients undergoing bariatric surgery and provides an overview of the effectiveness of various available vitamin B12 formulations.

Methods: To identify the relevant literature, a systematic review of MEDLINE was conducted from the earliest dates through September 2012 for English-language articles describing the prevention and management of vitamin B12 deficiency in patients undergoing bariatric surgery.

Results: Intramuscular vitamin B12 continues to be the gold standard of therapy for vitamin B12 deficiency, especially in symptomatic patients. In select patients with asymptomatic vitamin B12 deficiency after Roux-en-Y gastric bypass (RYGB), high-dose oral cyanocobalamin should be given a consideration, especially when there are concerns with the adherence to intramuscular therapy or if compliance comes into question. Unlike patients post-RYGB, those undergoing restrictive procedures such as gastric banding and sleeve gastrectomy may be maintained postoperatively on a lower-dose daily vitamin B12 supplementation. Efficacy data of nasal and sublingual routes for maintenance therapy is currently awaited.

Conclusion: Patients undergoing bariatric surgery must be continuously educated on proper nutrition, the risk of developing significant vitamin B12 deficiency, and the role of supplements in avoiding catastrophic consequences.