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Anemia after Gastric Bypass


One of the side effects or complications that occur after a gastric bypass surgery is a medical condition called anemia. Studies show that almost 2/3 of post-operative gastric bypass patients experience anemia.


Anemia is a nutritional deficiency characterized by hemoglobin or red blood cell counts that are below normal levels. Men with red blood cell count levels of 13.5 grams and lower, and women with red blood cell count levels of 12 grams and lower are said to have anemia.

Gastric Bypass Surgery

Gastric bypass surgery is a type of bariatric or weight loss surgery, and is also the most common.  The procedure involves making a portion of the stomach into a small pouch, and thereafter attaching it to the small intestine, particularly in the distal segment, avoiding the duodenum and a part of the jejunum.

In short, gastric bypass surgery is gut manipulation, which naturally affects the absorption of nutrients into the body. This leads to the development of nutritional deficiencies, anemia being the most common.

Iron Deficiency

The nutrient iron is mostly found in red meat and vegetables. The duodenum and jejunum are largely responsible for effective iron absorption into the body, and thus the interference caused by gastric bypass surgery may cause iron deficiency.

Iron deficiency is thought to be the common cause of anemia in post-operative gastric bypass patients. However, not all anemia’s in such patients are caused by iron deficiency.

Vitamin B-12 Deficiency

One study showed that 29% of post-operative gastric bypass patients observed suffered from below normal levels of vitamin B-12.

Vitamin B-12, which is found mostly in meat and dairy, is another nutrient which, when deprived of, can cause anemia. Gastric bypass patients have the tendency to suffer from vitamin B-12 deficiency because the breakdown of vitamin B12 is impaired with the bypass of the duodenum.


Expert Opinion

Quote:  “Iron-deficiency anemia is a common complication of gastric bypass and is more pronounced in menstruating females. There is also a risk of other micronutrient deficiencies, such as vitamin B12 and calcium deficiencies. These require correction in their own right.”

Source:   Geoffrey Bihl, MD  Iron Deficiency and Gastric Bypass Surgery

Medscape Today (

Quote:   “Following surgery, a patient’s body must get necessary nutrients from less food with a smaller, less effective digestive system. Although helpful in reducing their caloric intake and fat absorption, these physical and metabolic changes leave them susceptible to nutritional deficiencies and subsequent anemia.”

Source: National Anemia Action Council  Monitoring Nutritional Deficiencies, Anemia in Bariatric Surgery Patients 




Nutrition in Clinical Practice
Anemia After Bariatric Surgery: More Than Just Iron Deficiency.
24.2 (2009): 217-26

Journal of the American Osteopathic Association
Nutritional Deficiencies After Gastric Bypass Surgery
109.11 (2009): 601-04

Anemia Symptoms, Causes, Diagnosis, and Treatment

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