Transferrin: Iron Transport in the Blood

What Is Transferrin

Transferrin is a protein produced by the liver whose primary function is to transport iron in the blood. It carries iron from the intestine (where it is absorbed from food) and from sites of old red blood cell breakdown to the bone marrow, where new red blood cells are produced. The amount of transferrin in the blood helps assess the state of iron metabolism and is an important part of the iron panel along with ferritin, iron, and transferrin saturation (TSAT).

The test is performed from a venous blood sample. Results are expressed in g/L units.

Reference Ranges

The most commonly used range for adults:

• 2.0 -- 3.6 g/L

These ranges may vary slightly between laboratories. Ranges for pregnant women, children, and older adults may differ. Always follow the reference ranges provided by your specific laboratory.

Why Transferrin May Be Elevated

• Iron deficiency -- this is the most common cause. When iron levels in the body are low, the liver produces more transferrin in an attempt to collect available iron more efficiently.
• Pregnancy -- physiologically increases due to increased iron requirements.
• Use of oral contraceptives -- estrogen stimulates transferrin production.
• Latent iron deficiency -- even when hemoglobin is still normal, transferrin may already be elevated.

Why Transferrin May Be Decreased

• Chronic diseases and inflammation -- during inflammatory processes, the liver reduces transferrin production (transferrin is a negative acute-phase protein).
• Liver diseases -- reduced protein synthesis.
• Nephrotic syndrome -- loss of transferrin through the kidneys.
• Nutritional deficiency -- especially protein deficiency.
• Iron overload (hemochromatosis) -- when iron is abundant, the body reduces transport protein production.

What to Do With Your Results

Transferrin alone does not provide the full picture -- it should be evaluated together with other iron panel markers:

• Ferritin reflects iron stores.
• Transferrin saturation (TSAT) -- how much transferrin is loaded with iron. Low TSAT (less than 20%) indicates iron deficiency; high TSAT (more than 50%) may indicate overload.
• Hemoglobin and red blood cell indices (MCV, MCH) -- whether anemia is already present.

If transferrin is elevated and ferritin is low, this is a characteristic sign of iron deficiency, even if hemoglobin is still normal. Your doctor may recommend dietary changes or iron supplements.

Tracking Over Time

Transferrin levels change slowly -- a repeat test is meaningful after 2-3 months, especially if iron supplementation therapy has been started. Monitoring is important for pregnant women, after blood loss, for vegetarians and vegans, and for patients with chronic disease.

Questions for Your Doctor

1. Do my transferrin and ferritin results indicate iron deficiency? 2. Should a transferrin saturation test be performed for a complete iron panel picture? 3. Could my chronic condition or medications be affecting my transferrin level? 4. When should I repeat the test to evaluate the trend?