Megaloblastic anemia after gastric bypass for obesity.

A megaloblastic anemia occurred in a middle-aged woman 6 years after a gastric bypass performed for obesity. Marked deficiencies of both vitamin B12 and folic acid were demonstrated. The Schilling test revealed that the vitamin B12 deficiency was due primarily to inadequate intrinsic factor. Vitamin and mineral deficiencies are relatively common long-term complications in gastric bypass patients, and result from multiple factors including restricted food intake, inadequate gastric digestion, and inadequate intrinsic factor. Bypass patients should receive vitamin-mineral supplements routinely and should have long-term periodic clinical and laboratory evaluation in order to prevent late hematological complications.