Iron, total iron binding capacity (TIBC), and ferritin tests are commonly ordered blood tests that provide important information about the amount of iron in the body for the diagnosis and monitoring of iron deficiency or iron overload conditions. Iron plays a key role in many body functions, so abnormalities in these tests can indicate an underlying problem.
Iron is an essential mineral that has several important functions in the body. It is a key component of hemoglobin, the protein in red blood cells that carries oxygen from the lungs to tissues and organs. Iron is also necessary for energy production, DNA synthesis, and immune system function.
The body tightly regulates iron levels through a careful balance of absorption from the diet and iron storage and transportation in the body. The major iron transport protein is transferrin, which picks up iron absorbed from the diet and delivers it to cells that need it. The major storage form of iron in the body is ferritin, a protein that can store up to 4500 iron atoms.
There are several key players in iron regulation and transport:
- Dietary iron (absorbed from food by the intestines)
- Transferrin (transports iron in the bloodstream)
- Ferritin (stores iron)
- Iron-containing enzymes and hemoglobin (contain and use iron)
When the balance of these components is altered, iron disorders can occur resulting in too much or too little iron in the body. Testing levels of iron, TIBC, and ferritin help identify abnormalities in iron status.
What is tested?
There are 3 main tests that make up the iron studies panel:
- Serum iron – measures the level of circulating iron bound to transferrin.
- Total iron binding capacity (TIBC) – measures blood levels of transferrin.
- Ferritin – measures the amount of stored iron.
Serum Iron
This test measures the amount of iron in the blood bound to transferrin. Reference ranges are generally 50-170 μg/dL for men and 40-150 μg/dL for women.
TIBC
TIBC measures the blood concentration of transferrin, the protein that transports iron. It represents the maximum amount of iron that can be carried in the blood. Normal TIBC ranges from 250-450 μg/dL.
Ferritin
Ferritin is the storage form of iron in the body. This test measures the amount of ferritin in the blood as an estimate of total body iron stores. Normal ranges are 12-300 ng/mL for men and 12-150 ng/mL for women.
When are iron studies tested?
Testing iron, TIBC, and ferritin may be recommended if a patient has symptoms or risk factors for iron disorders, including:
- Fatigue/weakness
- Pallor
- Shortness of breath
- Fast heartbeat
- Headaches
- Dizziness
- Spoon-shaped nails
- Inflammation/pain in tongue
- Poor appetite
- Heavy menstrual bleeding
- GI bleeding
- Frequent blood donations
- Pregnancy
- Poor diet/malabsorption
- Family history of iron disorders
Doctors may order iron studies as part of routine wellness screening as well. They may also be ordered to monitor iron levels during and after treatment for iron deficiency or overload.
What do abnormal results mean?
Abnormal iron, TIBC, and ferritin levels can indicate various iron disorders. The pattern of high/low levels provides clues to the underlying cause:
| Disorder | Serum Iron | TIBC | Ferritin |
|---|---|---|---|
| Iron deficiency | Low | High | Low |
| Anemia of chronic disease | Low | Low/normal | Normal/high |
| Hemochromatosis | High | Low | High |
| Iron poisoning | High | High | Normal |
Some key abnormalities:
- Low ferritin – Indicates iron deficiency and depleted iron stores. Most common in menstruating women.
- High ferritin and high iron – Indicates iron overload conditions like hemochromatosis where excess iron is deposited in tissues.
- Low iron and TIBC, normal/high ferritin – Suggests anemia of chronic disease where inflammation causes iron to get trapped in storage sites.
- Low iron, high TIBC, low ferritin – Classic findings in iron deficiency anemia from blood loss, malnutrition, etc.
What causes iron disorders?
There are several potential causes of abnormal iron studies results:
Iron Deficiency
This occurs when iron intake is insufficient to keep up with the body’s demands. Causes include:
- Inadequate dietary iron
- Malabsorption from celiac disease, IBD, etc.
- Pregnancy/growth demands
- Blood loss from menstruation, GI bleeds, surgery, etc.
- Frequent blood donations
Anemia of Chronic Disease
Inflammation from chronic illness can cause low iron and anemia. Diseases include:
- Kidney disease
- Cancer
- Rheumatoid arthritis
- Infections
Inflammation causes iron to be trapped in macrophages and cells, unavailable for red blood cell production.
Iron Overload
Excess iron accumulation occurs in conditions like:
- Hereditary hemochromatosis – Genetic disorder causing excessive iron absorption.
- Repeated blood transfusions – For blood disorders like thalassemia.
- Excess iron intake – From diet, supplements, or medications.
- Liver disease – Impairs release of iron into blood.
Iron overload can damage the liver, heart, joints, and endocrine organs over time.
How are iron disorders treated?
Treatment depends on the specific iron disorder:
Iron Deficiency
- Oral iron supplements to replenish iron stores
- Underlying cause addressed – e.g. anti-inflammatories for inflammatory bowel disease
- Diet modification to increase iron intake
- Iron injections or IV iron for severe deficiency
- Blood transfusion if anemia is severe with hemodynamic instability
Iron Overload
- Phlebotomy to remove excess iron
- Iron chelators taken orally or intravenously to bind excess iron
- Manage underlying cause – e.g. treat liver disease, reduce transfusions
- Avoid iron supplements and high-iron foods
Takeaway points
- Iron studies (iron, TIBC, ferritin) evaluate iron levels and storage in the body.
- They help diagnose and monitor iron deficiency and overload conditions.
- Low ferritin indicates depleted iron stores.
- High ferritin with high iron indicates iron overload.
- Causes include inadequate iron intake, blood loss, inflammation, genetic conditions, etc.
- Treatment aims to address the underlying cause and normalize iron levels.
Conclusion
The iron, TIBC, and ferritin panel provides key information about iron status in the body. Abnormal results on these tests can identify iron deficiency or excess states and prompt further evaluation of underlying disorders leading to these conditions. Diagnosing the cause of iron abnormalities is key, as treatment relies on addressing the fundamental problem. With appropriate treatment guided by iron studies, iron levels can be restored to normal, improving patients’ symptoms and preventing complications of prolonged iron imbalance.
