Treatment of Vitamin B12 Deficiency after Gastric Surgery for Severe Obesity.

BACKGROUND: Vitamin B12 deficiency after gastric surgery for obesity is due to a failure of separation of vitamin B12, from protein foodstuffs and to a failure of absorption of crystalline vitamin B12 in the presence of intrinsic factor. The purpose of this study was to determine which of four oral doses of crystalline vitamin B12 was most effective in treating vitamin B12 deficiency in 102 patients. METHODS AND RESULTS: At time of entry into the study, the patients had a serum vitamin B12, < 100 pmol L(1), were 29.