Iron Tests Explained: Ferritin, Serum Iron, TIBC, Transferrin Saturation and Hemoglobin

What each test measures

MedlinePlus describes the main iron tests like this.

Transferrin saturation, which you may see reported, compares iron in the blood with the protein that carries it. The NHS describes the test as checking how much iron in the blood is bound to the protein transferrin, and lists it alongside a serum ferritin test when checking for haemochromatosis. [3] NIDDK says a high ratio of iron to transferrin in the blood may suggest hemochromatosis. [4]

Evidence labels on this page: established means described as standard practice by the health agencies; limited means the sources describe uncertainty.

Ferritin: stored iron, but not a perfect gauge

Ferritin is a protein that binds to iron and stores it in the body. [5] Lower than normal ferritin may mean iron deficiency anemia or another condition related to low iron. [5] Higher than normal levels can be caused by too much iron in the body, but MedlinePlus lists other causes too: inflammation (such as infection or surgery), an autoimmune disorder, liver disease, cancer, obesity, alcohol use disorder and hyperthyroidism. [5] So a high ferritin does not by itself prove iron overload.

The World Health Organization says ferritin levels are low in iron-deficient people and high in iron-loaded people, and that accurate measurement along with clinical and laboratory evaluation can guide the right action. [6] This page does not give cut-off numbers: we did not read a guideline table, and cut-offs differ by lab, age, pregnancy and whether inflammation is present.

What can change the results

• Time of day and fasting. The amount of iron in your blood varies through the day and may be higher in the morning, and a provider may ask you to fast for 12 hours. [1]
• Medicines. MedlinePlus says some medicines, including birth control pills and estrogen treatments, can affect iron levels, and iron levels may be lower for women during menstrual cycles. [1] Certain medicines can also raise or lower ferritin. [5]
• Lab ranges. Reference ranges vary with the laboratory used and with age and sex. [2]
• Not normal does not always mean disease. If results are not normal it does not necessarily mean a medical condition that needs treatment. [1]
• Supplements. The pages we read do not describe how iron supplements taken shortly before a test change results. Proper evidence not found there (searched MedlinePlus iron, ferritin and hemoglobin test pages); ask the lab or clinician how to prepare.

What results can and cannot show

Low iron tests may point to iron deficiency anemia, another type of anemia, or thalassemia. High iron tests may point to hemochromatosis, lead poisoning or liver disease. [1] Not everyone with low iron has anemia. [1] A hemoglobin test cannot tell you what is causing an abnormal level. [2] Tests for the cause of blood loss, such as colonoscopy, are separate. [7]

Who should talk to a clinician

Anyone with an abnormal result, a family history of hemochromatosis, heavy periods, a digestive condition, pregnancy or kidney or liver disease should have results interpreted by a clinician. Treatment of low or high iron is clinician-led. At-home and hair-based mineral panels are not described as diagnostic by the sources we read; see Hair mineral analysis and Deficiency testing and its limits.

Related pages

Iron deficiency and iron-deficiency anemia, Iron overload and hemochromatosis and Iron.