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What Iron Supplements Can Gastric Bypass Patients Take?

author image Debra McKenzie
Based in Chapel Hill, N.C., Debra McKenzie has been writing since 2001. Her work has appeared in journals, including "JADA" and "Obesity Research," and in the textbook "Nutrition in the Prevention and Treatment of Disease." She holds a Master of Science in nutrition from University of Vermont and completed her dietetic internship at Meredith College.
What Iron Supplements Can Gastric Bypass Patients Take?
Vitamins and mineral supplements are required for life after bariatric surgery. Photo Credit karenfoleyphotography/iStock/Getty Images

A major complication after gastric bypass surgery is malnutrition caused by the smaller quantity of food consumed and the decreased ability to digest and absorb certain nutrients. It is recommended that individuals who have had gastric bypass take vitamin and mineral supplements every day for life to prevent malnutrition. Iron is one of the minerals affected by the surgery.

Iron Absorption

A study published in the "American Journal of Clinical Nutrition" in 2009 found that gastric bypass surgery reduces both iron absorption and iron status. Researchers followed 51 patients for 18 months after surgery. Iron absorption from both supplements and food at 6 months decreased to between 32.7 and 40.3 percent of the initial values, with little change by 18 months. Thirty-eight percent of subjects were anemic at 18 months compared with 1.5 percent initially.

Iron Status

The serum ferritin level is directly related to the iron stores in the body and is a common test for anemia. Normal levels range between 12 to 150 ng/mL for women and 12 to 300 ng/mL for men. According to the National Institutes of Health, signs of low iron levels include feeling tired and weak; decreased performance; difficulty maintaining body temperature; decreased immune function; an inflamed tongue; and pica, a craving for non-nutritive substances such as ice, dirt and clay.


Most physicians recommend taking an iron supplement after gastric bypass surgery in addition to the iron available in a multivitamin after solid food can be consumed. Ferrous fumarate and ferrous gluconate are available over the counter and are the most absorbable forms of iron, according to the West Penn Allegheny Health System. Iron and calcium supplements should be taken at least two hours apart. Vitamin C helps the body absorb iron, so iron should be taken with vitamin C supplements or foods that contain vitamin C, such as fruits and vegetables. Ask your doctor about recommended brands and amounts that are right for you. Supplements specifically formulated for bariatric patients are available.

Potential Side Effects

Large doses of iron can cause gastrointestinal upset, including nausea, vomiting, constipation, diarrhea and abdominal distress. Take iron with meals to increase absorption and prevent stomach upset. You may also find it beneficial to take the prescribed dose in two to three equally spaced doses because the Office of Dietary Supplements reports the amount of iron absorbed actually decreases with larger doses.

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