Diagnosing Iron Deficiency Anemia — Ferritin Thresholds, Confirmatory Testing, and Workup

An expert discusses how clinicians should approach the diagnosis of iron deficiency anemia, including appropriate ferritin thresholds, confirmatory laboratory testing, and the broader workup needed to identify the underlying cause.

Iron deficiency anemia (IDA) is among the most common hematologic conditions worldwide, affecting up to 4% of men and up to 40% of premenopausal women. Establishing the diagnosis begins with ferritin measurement, and the American Gastroenterological Association (AGA) recommends a ferritin cutoff of 45 µg/dL in individuals with anemia. This threshold, however, requires clinical context: inflammatory conditions can elevate ferritin independently of iron stores, meaning a patient may have true iron deficiency anemia despite a ferritin level that appears within or above the normal range. Confirmatory testing in these and other diagnostically uncertain cases may include transferrin saturation, soluble transferrin receptor, or reticulocyte hemoglobin, though significant variation exists in how these tests are applied in real-world practice. The American Society of Hematology (ASH) guideline panel has identified diagnostic thresholds — including those appropriate for pregnant women, children, and patients with inflammatory conditions — as a priority question in its ongoing evidence synthesis.

Once iron deficiency is confirmed, identifying its source is essential and shapes subsequent management. The underlying cause generally falls into 1 of 3 categories: inadequate iron intake, excess loss through output, or increased utilization. In clinical practice, the workup commonly includes assessment of dietary iron intake, evaluation of menstrual losses in premenopausal women, and investigation of gastrointestinal causes — whether blood loss or impaired absorption. Management frequently involves a multidisciplinary team extending beyond hematology to include primary care, gastroenterology, and nutrition, depending on the suspected etiology. The ASH guidelines have similarly flagged wide variation in diagnostic testing practices as a priority area for their forthcoming evidence synthesis, reflecting the degree to which current practice lacks standardization across care settings.

In this video discussion on iron deficiency anemia management, Richard Godby, MD, walks through the diagnostic framework clinicians should apply when IDA is suspected or confirmed. Godby emphasizes that the ferritin threshold recommended by the AGA provides a practical starting point but must be interpreted in light of the patient's inflammatory status, and that confirmatory testing should be pursued when the clinical picture and ferritin level are discordant. He underscores that arriving at a diagnosis of IDA is only the first step — understanding why the patient is iron deficient is equally important and directly determines the management approach, the specialists who need to be involved, and the likelihood that oral iron supplementation alone will be sufficient.