The test you should be doing, but aren't: Reframing ferritin testing in clinical practice
Industry Buzz
The tests to find iron deficiency are straightforward. You can get a ferritin level and the ferritin level is equal to the total iron your body stores. If the ferritin level is low, it's iron deficiency. If the ferritin level is above a certain level, it's clearly not iron deficiency.
—Richard Eisenstaedt, MD, to the American Medical Association
There are a lot of people who are iron-deficient for so long and don't even know. Picking it up early can lead to it being treated early and potentially prevent anemia and other symptoms.
—Imo J. Akpan, MD, to Women's Health
Iron deficiency is one of the most common conditions physicians encounter–and one that remains persistently underdiagnosed.
The main issue is the approach. Hemoglobin is still widely used as the primary screening tool, while ferritin–the most sensitive marker of iron stores–is often ordered too late.
Why ferritin testing matters
Ferritin declines early in iron depletion, often well before anemia develops, making it a more sensitive indicator than hemoglobin alone.[] Yet in practice, testing is delayed until anemia is suspected, which can result in missed or late diagnoses.
This matters because iron deficiency has clinical consequences beyond hematology. Even without anemia, patients may present with fatigue and worsening mental health symptoms, including anxiety and depression.[]
"The tests to find iron deficiency are straightforward,” Richard Eisenstaedt, MD, a primary care internist at Jefferson Abington Hospital, told the American Medical Association.[] “You can get a ferritin level and the ferritin level is equal to the total iron your body stores. If the ferritin level is low, it's iron deficiency. If the ferritin level is above a certain level, it's clearly not iron deficiency."
A normal hemoglobin level does not exclude clinically meaningful deficiency, and relying on it can delay treatment.
What patients stand to benefit most
Several patient populations are particularly likely to be missed without routine ferritin testing.
Women of reproductive age are a clear example. During pregnancy, iron requirements increase substantially, yet ferritin testing is not consistently performed. Studies show screening remains insufficient, meaning many cases of deficiency go undetected until anemia develops.[] This is especially concerning given iron's critical role in fetal development and maternal outcomes.[]
Women with heavy menstrual bleeding are also a high-risk group, with research suggesting a substantial burden of undiagnosed iron deficiency that supports more proactive screening.[]
Pediatric patients more broadly face similar challenges. Iron deficiency in children and teens can affect neurodevelopment, immune function, and growth. It often precedes anemia, reinforcing the value of ferritin testing for early identification.[]
Athletes–particularly endurance runners–are also at increased risk. Hemolysis, sweat loss, and increased physiologic demand can lead to iron depletion. In these patients, declines in energy and performance may occur before anemia is present, making ferritin a useful screening tool.[]
Ferritin testing is often overlooked in patients presenting with nonspecific symptoms such as fatigue. Iron deficiency is a common but underrecognized contributor in these cases, especially when hemoglobin levels remain normal, which can lead to prolonged symptoms and delayed diagnosis.[]
"There are a lot of people who are iron-deficient for so long and don't even know. Picking it up early can lead to it being treated early and potentially prevent anemia and other symptoms," Imo J. Akpan, MD, a hematologist at New York-Presbyterian and Columbia University Irving Medical Center, told Women's Health.[]
What this means for clinical practice
Incorporating ferritin testing earlier in the diagnostic process can shift care in meaningful ways. It enables earlier diagnosis by identifying iron deficiency before anemia develops, allowing for timely intervention and potentially preventing progression.[]
It can also help physicians more accurately attribute symptoms. Fatigue and mood disturbances are often nonspecific, but low ferritin may provide a clear, treatable explanation, reducing the need for expensive diagnostic workups.[]
Broader use of ferritin testing—combined with updated diagnostic thresholds—may improve overall detection rates. As the evidence suggests, rethinking what constitutes a "normal" ferritin level could significantly increase the number of patients appropriately diagnosed and treated.[]
Ultimately, ferritin testing is a simple, accessible tool that is already available in most clinical settings. The opportunity lies in using it more effectively.