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Obes Surg. 1995 May;5(2):154-158.

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

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Department of Surgery and Medicine, Division of Clinical Biochemistry, Royal Victoria Hospital, McGill University, Montreal, Quebec, H3A 1A1, Canada.



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.


At time of entry into the study, the patients had a serum vitamin B12, < 100 pmol L(1), were 29.9 +/- 21.7 months post-op, were 37 +/- 8 years old and had a body mass index of 30 +/- 6 kg m (2). Eight (8%) had had a vertical banded gastroplasty and 94 (92%) a gastric bypass. For the first 3 months all patients received 350 µg per day of crystalline vitamin B12, and all increased their serum vitamin B12 levels to over 100 pmol L(1). The patients were then assigned to receive for a further 3 month period one of four oral doses of crystalline vitamin B12-100 µg, 250 µg, 350 µg and 600 µg. Serum vitamin B12 levels were greater than 150 pmol L(1) after 6 months in 83.3% of patients who received 100 µg; 92.3% of patients who received 250, µg; 94.7% after 350 µg and 95.2% after 600 µg (p%0.525).


At least 350 µg per day is the appropriate oral dose of crystalline vitamin B12 after gastric surgery for obesity to correct low serum vitamin B12 levels in 95% of patients.


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