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The Complexities of Iron Deficiency in Patients After Bariatric Surgery

surgical instruments laid out for use


To the Editor:

Iron deficiency is one of the most common micronutrient deficiencies after bariatric surgery and is often overlooked by healthcare providers when patients present with vague symptoms or laboratory results do not demonstrate straightforward iron-deficiency anemia. Thus, it is imperative that providers order tests and interpret laboratory results carefully so they can appropriately screen, diagnose, and treat iron deficiency after bariatric surgery.1

Case Report

A 34-year-old white woman with a history of morbid obesity presented to the clinic in January 2016, 4 months after Roux-en-Y gastric bypass surgery. Overall, she felt well and said her energy level was “ok.” She confirmed adherence to her daily vitamins (2 multivitamins, calcium and vitamin D3, biotin [vitamin B2] and sublingual vitamin B12), fluids, and protein requirements. However, she admitted to occasional abdominal pain, nausea, and vomiting with meat and cheese ingestion, so she would avoid these foods. Review of systems was negative, except she admitted to increased hair loss since surgery and occasional orthostatic dizziness the last few weeks. The physical examination, vital signs, basic metabolic panel, and thyroid-stimulating hormone 2.30 (reference, 0.35–4 uIU/mL) results were unremarkable. The laboratory results are listed in Table. She received oral ferrous sulfate for the treatment of iron deficiency, and 3 months later, her symptoms of orthostatic dizziness and energy were improved.


Iron deficiency is common after bariatric surgery because patients tend to eat less food after surgery, often less meat, which leads to decreased intake of heme iron. Also, gastric hypochlorhydria after surgery impairs iron absorption, and bypass of the duodenum in the setting of Roux-en-Y gastric bypass surgery impairs reduction of iron to the ferrous state (absorbable iron).23

In patients after bariatric surgery, routine laboratory testing to assess for iron deficiency should include complete blood count, ferritin, iron concentration, and total iron-binding capacity that is used to calculate transferrin saturation.145 Iron deficiency and iron-deficiency anemia are on a spectrum, in which iron deficiency appears first, reflected by a low serum ferritin (<30 ng/mL) indicating low iron stores. Low serum ferritin in conjunction with low transferrin saturation is diagnostic of iron deficiency.45 Isolated low serum iron concentration as an indicator of iron deficiency or iron-deficiency anemia is less useful because of internal diurnal variation and susceptibility to external influences, and thus should not be treated.5 Ferritin is the most sensitive and specific laboratory test for iron deficiency in healthy adults and is 92% sensitive and 83% specific for iron-deficiency anemia, but data are limited for this laboratory test’s accuracy in patients after bariatric surgery.6 Of note, an elevation of ferritin, an acute phase reactant, has been reported only during the first month after bariatric surgery and usually trends down at 6 months postoperatively.2

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-Amanda Velazquez, MD, Caroline M. Apovian, MD, Nawfal W. Istfan, MD, PhD

This article originally appeared in the July 2017 issue of The American Journal of Medicine.

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