Transferrin
A protein that carries iron through your blood. It tends to rise when iron stores are low and fall with inflammation, liver problems or low protein.
AI-verified against cited sources. Awaiting expert reviewAlso called TfLOINC 3034-6
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The usual range for Transferrin depends on sex. Choose female or male above to see where you stand.
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What it is
Transferrin is the protein that carries iron around your body in the blood. It picks iron up from food and from your stores and delivers it where it is needed, including the bone marrow, where red blood cells are made. Your body makes more transferrin when iron is in short supply. This test measures how much transferrin is in your blood. It is read alongside serum iron, transferrin saturation and total iron-binding capacity (TIBC), which measure related things.
Why it matters
Transferrin helps your clinician work out why iron or hemoglobin is off. It usually goes up when iron stores are low. With inflammation, long-term illness, liver disease or low protein levels it tends to be low or normal. Transferrin also tracks nutritional status. It doesn't point to a cause on its own, so it is read with serum iron, transferrin saturation and ferritin.
If it’s low
A low transferrin means there is less carrier protein in your blood than usual. This often goes along with inflammation, long-term illness, low protein levels or liver disease. It can also be slightly low when the body holds extra iron.
Common causes
- Inflammation or infection
- Long-term (chronic) illness
- Low protein levels from poor nutrition or protein loss through the kidneys
- Chronic liver disease, such as cirrhosis
- Hemolytic anemia, where red blood cells break down early
- Iron overload conditions, including the inherited condition hemochromatosis
What can help
- Ask whether CRP, albumin or liver tests would help explain it
- Ask your clinician to read it together with serum iron, transferrin saturation and ferritin
If it’s high
A high transferrin most often fits with low iron stores, because the body makes more carrier protein when iron is scarce. It also runs higher in late pregnancy and with estrogen-containing birth control, where it does not mean low iron.
Common causes
- Iron deficiency (low iron stores)
- Pregnancy, especially late pregnancy
- Estrogen-containing birth control pills
- Ongoing blood loss, such as heavy periods
- Not enough iron in the diet
- Acute viral hepatitis (transferrin can be high along with serum iron and ferritin)
What can help
- Ask your clinician to read it together with serum iron, transferrin saturation and ferritin
- If iron stores are low, ask about the cause and whether iron treatment is right for you
- Eat iron-rich foods such as meat, fish, beans, lentils and fortified cereals
Usual ranges
What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.
The usual range depends on sex and age. Choose women or men to see the one that applies.
See Transferrin by age and sex, with the U.S. survey numbers where they exist.
What can affect your result
- Late pregnancy and estrogen-containing birth control raise transferrin
- Inflammation, infection, chronic liver disease and low protein levels lower it
- Low iron stores raise it, and iron overload conditions can lower it slightly
- Fasting state: ARUP prefers a fasting sample
- Tube type: Labcorp and ARUP do not accept EDTA plasma, and hemolyzed samples are rejected
- Units and methods: US labs report mg/dL, while many other countries use g/L
- Estrogen-containing birth control raises transferrin and TIBC, usually with normal transferrin saturation. Transferrin is also higher in late pregnancy (Labcorp).
- Inflammation, infection, chronic liver disease and low protein levels lower transferrin.
- Labcorp and ARUP reject EDTA plasma, and both reject hemolyzed samples. Serum or heparin plasma is accepted.
- Labs use different methods and some report in mg/dL while others use g/L, so compare results from the same lab when you can.
Morning, because it is usually drawn with serum iron, which tends to be higher in the morning. Moves over days to weeks as iron stores and illness change. It does not swing from meal to meal the way serum iron does.
When to talk to a clinician
A transferrin result on its own is rarely urgent, and labs don't usually set an urgent limit for it. Talk with a clinician if it is outside your lab's range together with tiredness, shortness of breath, dizziness, or a low blood count, ferritin or serum iron.
Questions you could ask
- How do my iron, transferrin and transferrin saturation fit together?
- Could pregnancy, birth control or low iron explain a high transferrin?
- Should we check ferritin and transferrin saturation too?
- Could inflammation, my protein intake or how my liver is working explain a low transferrin?
- Should we look at CRP, albumin or liver tests?
Questions people ask
What is the difference between transferrin, TIBC and transferrin saturation?
Transferrin is the carrier protein itself. TIBC is how much iron it could carry in total, so the two move together. Transferrin saturation is the share of that capacity that is filled with iron, which is serum iron divided by TIBC. Which of these your lab reports varies.
Why is my transferrin high when my iron is normal?
Transferrin rises when iron stores are low, in late pregnancy, and with estrogen-containing birth control. Labcorp notes that with birth control, transferrin and TIBC are higher but saturation stays normal. Ferritin and transferrin saturation help sort out which it is.
How do I convert transferrin units?
Divide mg/dL by 100 to get g/L, so 300 mg/dL is 3.0 g/L. To go the other way, multiply g/L by 100.
Show the science and sources
Units
- 1 mg/dL = 1 mg/dL
- 1 mg/dL = 0.01 g/L
Open the Transferrin unit converter
Is a change real?
Transferrin naturally varies about 3.4% from test to test in the same healthy person. Between two results from the same lab, a change of roughly 12% or more is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: The European Biological Variation Study (EuBIVAS): a summary report.
For clinicians and researchers
Transferrin is a glycoprotein made mainly in the liver that carries ferric iron in plasma, and it is normally only about one-third saturated (Labcorp). It behaves as a negative acute-phase protein, so it falls in inflammation. Labcorp (test 004937) lists an immunologic method and ARUP (test 0050570) lists quantitative immunoturbidimetry; both report mg/dL (1 g/L = 100 mg/dL). Labcorp states that transferrin accounts for about 50% to 70% of serum iron-binding capacity and is not the same as TIBC. Mayo Clinic Laboratories lists its TIBC method as turbidity/calculation. A 2022 comparison of about 250 samples found that direct-method TIBC correlated strongly with serum transferrin (r = 0.888), while TIBC calculated as iron plus UIBC (r = 0.725) or by an indirect method (r = 0.748) correlated less well, so TIBC and transferrin results are not always interchangeable between labs. Reference intervals in mg/dL: Labcorp 177–329 for men and 192–364 for women aged 18 to 80, and 149–313 over 80; ARUP 200–360 with no sex or age split. Labcorp's interpretive notes describe typical patterns. In uncomplicated iron deficiency, transferrin is high, iron is low and saturation is low. In anemia of chronic disease, transferrin is low to normal, iron is low and saturation is low or normal. In hemolytic anemias, transferrin is normal to low, iron is high and saturation is high. In hemochromatosis, transferrin is slightly low, iron is high and saturation is very high. Transferrin and TIBC are raised by oral contraceptives with normal saturation, and lowered by protein depletion and many inflammatory states. Transferrin may not rise in iron deficiency when there is severe protein malnutrition (Labcorp). Carbohydrate-deficient transferrin (CDT) is a separate test and is not measured here.
LOINC 3034-6 (primary), 22674-6, 35229-4. Specimen: serum-or-plasma.
Sources
- Transferrin (test 004937), Labcorp
- Transferrin, Serum (test 0050570), ARUP Laboratories
- Transferrin sample report (test 004937), Labcorp
- Iron and Total Iron-binding Capacity (TIBC) (test 001321), Labcorp
- Iron and Total Iron-Binding Capacity, Serum (test SFEC), Mayo Clinic Laboratories
- Iron Tests, MedlinePlus (NIH)
- Appropriate Method of TIBC Estimation in Reference to Serum Transferrin Levels, Journal of Laboratory Physicians (2022)
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.