As weight loss begins to slow down after gastric bypass, the risk of nutritional problems increases. This is due to dysfunctional or bypassed small bowel. B12 and iron deficiency are two of the most common problems and often do not respond to typical multivitamin supplementation.
Iron deficiency after gastric bypass is usually only seen in menstruating women or in patients who are actively and chronically bleeding. Ferritin or iron levels and erythrocyte counts need to be monitored after a bypass, as iron deficiency can develop early after surgery or years later; one study found that iron stores continuously declined up to 7 years after bypass surgery. Due to bypass of the lower stomach, in which iron is absorbed, it is very difficult for iron-deficient patients to absorb sufficient oral iron. Many cannot tolerate read meat. Intramuscular iron can be impractical over the long run. Usually, intravenous iron dextran or iron sucrose is used regularly; many patients require intravenous iron several times a year. This is done as an outpatient procedure and is well tolerated by patients.
Brolin RE et al. Prophylactic iron supplementation after Roux-en Y gastric bypass: a prospective, double blind, randomized study. Arch Surg. 1998;133(7):740-744.
Dimitrios V Avgerinos, Omar H Llaguna, Matthew Seigerman, Amanda J Lefkowitz, and I Michael Leitman
Incidence and risk factors for the development of anemia following gastric bypass surgery, World J Gastroenterol. 2010 April 21; 16(15): 1867–1870.
Love AL, Billett HH. Obesity, bariatric surgery, and iron deficiency: true, true, true and related.Am J Hematol. 2008 May;83(5):403-9.