Ferritin Test Explained: What Low or High Ferritin Means

Your body stores most of its spare iron inside ferritin, mainly in the liver, spleen and bone marrow. A small amount of ferritin circulates in the blood, and its level rises and falls with your iron stores. That makes ferritin the most useful single blood test for spotting iron deficiency early, before anemia develops.

A low ferritin almost always means your iron stores are running low. Common causes are heavy periods, pregnancy, blood donation, a diet low in iron, and blood loss from the gut, for example from ulcers, polyps or regular use of anti-inflammatory painkillers. Problems absorbing iron, as in coeliac disease, can also lower it. In adults, especially men and women after menopause, unexplained low iron usually needs a check for a hidden cause.

Ferritin falls before hemoglobin does, so you can have low iron stores with a normal blood count. Some people in this stage feel tired, short of breath on exertion, notice hair shedding or restless legs, though these symptoms have many causes. Your clinician may look at your hemoglobin, MCV, MCH and transferrin saturation with ferritin to see the full picture.

Ferritin also rises as part of the body’s response to inflammation, so a high result most often reflects an infection, an inflammatory condition, fatty liver, regular alcohol use, obesity or metabolic syndrome rather than extra iron. Less often it points to iron overload, such as hereditary hemochromatosis, or to repeated blood transfusions. Transferrin saturation helps tell these apart: when it is also high, iron overload is more likely.

Because inflammation pushes ferritin up, a normal or high result can hide low iron in someone who is unwell. Clinicians often check CRP, transferrin saturation, serum iron and a complete blood count alongside ferritin. A single mildly abnormal result is common and is often repeated.

Low iron stores are usually treated with iron-rich foods and often an iron supplement, together with finding the cause. Taking iron with vitamin C and apart from tea, coffee and calcium can improve absorption. Do not start high-dose iron without advice, because too much iron is harmful. For high ferritin, the plan depends on the cause; treating inflammation, fatty liver or alcohol use often brings it down, and iron overload is managed by a specialist.