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Iron Tests
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

Iron Tests

Iron tests measure substances in your blood to determine if your iron levels are too low or too high, helping to diagnose conditions like anemia or iron overload.

Overview

Iron is a mineral essential for growth and development. Your body uses it to produce hemoglobin, a protein in red blood cells that carries oxygen from the lungs to the rest of the body. Iron is also vital for healthy muscles, bone marrow, organ function, and the production of certain hormones.

While most people in the United States get enough iron through food or supplements, certain groups are at higher risk for deficiency, including:

  • Those with heavy periods
  • Pregnant or breastfeeding individuals
  • Infants, particularly those who are premature or have low birth weight
  • Frequent blood donors
  • People with cancer, certain digestive diseases, or heart failure

Iron levels that are too low or too high can cause health concerns. Low iron is the most common cause of anemia, a condition where your blood has a lower-than-normal amount of red blood cells.

Types of Iron Tests

Health care providers may order one or several of the following tests to better understand your iron status:

  • Serum iron test: Measures the amount of iron in the blood.
  • Transferrin test: Measures transferrin, a protein that moves iron throughout the body.
  • Total iron-binding capacity (TIBC): Measures how well iron attaches to transferrin and other proteins in the blood.
  • Ferritin blood test: Measures how much iron is stored in the body.

What are they used for?

Iron tests are primarily used to:

  • Check for low iron levels, which may indicate anemia.
  • Diagnose different types of anemia.
  • Check for high iron levels, which could indicate hemochromatosis (iron overload).
  • Measure iron stored in the liver to check for liver disease.
  • Check for restless legs syndrome.
  • Check for adult Still disease (AOSD).
  • Monitor the effectiveness of treatments for iron deficiency or excess iron.

Symptoms and Diagnosis

You may need testing if you exhibit symptoms of abnormal iron levels. Symptoms of low iron include weakness, fatigue, dizziness, shortness of breath, and arrhythmia. Symptoms of high iron include weakness, fatigue, joint pain (often in the knees or hands), abdominal pain, loss of interest in sex or erectile dysfunction, and changes in skin color (gray, metallic, or bronze).

If results show low levels, it may indicate iron deficiency anemia, other types of anemia, or thalassemia. High levels may indicate hemochromatosis, lead poisoning, or liver disease. Note that some medications, such as birth control pills and estrogen treatments, can affect results.

Test Procedure and Preparation

A health care professional will collect a blood sample from a vein in your arm. The process typically takes less than five minutes. Your provider may ask you to fast for 12 hours before the test, which is usually performed in the morning. There is very little risk, though you may experience slight pain or bruising at the needle site.

Frequently Asked Questions

serum iron test measures the amount of circulating iron in the blood, giving a snapshot of how much iron is currently available. A ferritin test measures stored iron, reflecting the body’s iron reserves. Doctors usually order a ferritin test first when iron deficiency is suspected, and a serum iron test along with TIBC or transferrin saturation to confirm the diagnosis or evaluate iron overload.
Yes, iron supplements can temporarily raise serum iron levels and alter ferritin readings. It is best to stop oral iron supplements for at least 24–48 hours before the test, unless your doctor advises otherwise. If you are on intravenous iron, inform the lab. Fasting is not required for most iron tests, but follow any specific instructions from your healthcare provider.
normal ferritin with low serum iron may suggest early iron deficiency that has not yet depleted iron stores, or it could indicate anemia of chronic disease where inflammation keeps ferritin normal or high while iron is sequestered. Your provider may repeat the tests or add markers of inflammation (CRP, ESR) to clarify the cause.
high TIBC (total iron‑binding capacity) often indicates iron deficiency, because the body produces more transferrin to capture more iron. Low TIBC can suggest anemia of chronic disease or hemochromatosis. Transferrin saturation (serum iron divided by TIBC) below 20% usually points to iron deficiency, while a saturation above 45% may indicate iron overload or hemochromatosis. Always discuss the numbers with your clinician, as they consider the full clinical picture.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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