In patients with anemia, the AGA recommends using a cutoff of 45 ng/mL over 15 ng/mL when using ferritin to diagnose iron deficiency. In patients with inflammatory conditions or chronic kidney disease, other laboratory tests such as C-reactive protein, transferrin saturation, or soluble transferrin saturation, may be needed in conjunction with ferritin to diagnose iron deficiency anemia.

In patients with iron-deficiency anemia, the AGA suggests against the use of routine gastric biopsies to diagnose atrophic gastritis.

In patients with iron deficiency anemia without other identifiable etiology after bidirectional endoscopy, the AGA suggests noninvasive testing for Helicobacter pylori, followed by treatment if positive, over no testing.

In asymptomatic adult patients with iron deficiency anemia and plausible celiac disease, the AGA suggests initial serologic testing, followed by small bowel biopsy only if positive, over routine small bowel biopsies. Celiac disease is a well-recognized cause of iron deficiency anemia, even in asymptomatic patients, and, therefore it must be considered in the differential diagnosis of iron deficiency anemia.

In asymptomatic postmenopausal women and men with iron deficiency anemia, the AGA recommends bidirectional endoscopy over no endoscopy.

In asymptomatic premenopausal women with iron deficiency anemia, the AGA suggests bidirectional endoscopy over iron replacement therapy only. Patients who place a high value on avoiding the small risk of endoscopy, particularly those who are young and might have other plausible reasons for IDA, and a low value on the very small risk of missing a gastrointestinal malignancy would reasonably select an initial course of iron replacement therapy and no initial bidirectional endoscopy.

In uncomplicated asymptomatic patients with iron deficiency anemia and negative bidirectional endoscopy, the AGA suggests a trial of initial iron supplementation over the routine use of video capsule endoscopy. Caution needs to be applied in patients with comorbid conditions where the identification of small bowel pathology will change medical management, such as the use of anticoagulation and/or antiplatelet therapy.