Transferrin test: normal range and what the result means

Transferrin is a protein made in the liver that binds iron in the blood and carries it from the intestine and from the body's iron stores (ferritin) to the bone marrow, where red blood cells are made. Because free iron in the blood would be toxic, almost all circulating iron travels bound to transferrin. In laboratories transferrin is often assessed indirectly — through total iron-binding capacity (TIBC), which shows how much more iron transferrin could still bind; TIBC closely reflects the amount of transferrin in the blood. When iron stores fall, the liver starts producing more transferrin in order to capture the available iron more efficiently — which is why transferrin (and TIBC) most often rises when iron is lacking. Conversely, with inflammation, a chronic illness, liver damage or iron overload, transferrin production decreases. The test is most often done together with iron, ferritin and transferrin saturation tests, so that a true iron deficiency can be told apart from a change caused by inflammation.

• When a full blood count shows a reduced haemoglobin or haematocrit — when iron-deficiency anaemia is suspected
• When there is tiredness, weakness, paleness, shortness of breath or dizziness
• When the iron or ferritin results are unclear and iron deficiency needs to be told apart from a change caused by inflammation
• When iron overload (haemochromatosis) or liver disease is suspected
• To monitor the course of treatment with iron preparations, or during pregnancy, when the need for iron increases

A raised transferrin most often shows that the body is short of iron — the liver produces more transferrin in order to capture the available iron more efficiently. According to the University of Rochester Medical Center health encyclopedia, a raised value is characteristic of iron-deficiency anaemia.

Causes of a raised result:

• Iron-deficiency anaemia — the body increases the amount of transferrin in order to capture more of the iron it has
• Late pregnancy, when the need for iron increases
• Oral hormonal contraceptives or other preparations containing oestrogen can raise the amount of transferrin

What to discuss with a doctor:

• Ferritin and the iron level in the blood — so that it is clear whether the iron stores really are exhausted
• The transferrin saturation percentage — it helps to assess iron status more precisely
• A full blood count — whether there are already signs of anaemia
• A possible cause of blood loss, especially in men and in women after the menopause

A lowered transferrin

A lowered transferrin is most often linked to inflammation, liver disease, poor nutrition or iron overload. According to the University of Rochester Medical Center health encyclopedia, a value lower than usual is characteristic of liver disease and of haemolytic anaemia.

Causes of a lowered result:

• Inflammation or a chronic illness — transferrin is a negative acute-phase protein, so its production decreases
• Liver diseases, including cirrhosis of the liver — the production of proteins, transferrin among them, is disrupted
• Not enough protein in the diet, or protein loss (for example through the kidneys)
• Iron overload in the body (haemochromatosis)
• Some forms of anaemia — haemolytic or pernicious anaemia, sickle cell anaemia

What to discuss with a doctor:

• Liver markers (ALT, AST, GGT) — to assess whether the cause is in the liver
• Ferritin and transferrin saturation — to tell iron overload apart from inflammation
• The total amount of protein in the blood, and an assessment of nutrition
• Inflammation markers, for example CRP

Transferrin is most often assessed together with the iron level in the blood, ferritin and the transferrin saturation percentage — together these markers make it possible to tell a real iron deficiency apart from a change caused by inflammation or a chronic illness.

Read next

• Iron blood test — the iron level in the blood, assessed together with transferrin
• Ferritin test — the body's iron stores, from which transferrin carries iron onward
• TIBC test — the indirect measurement that closely reflects the amount of transferrin
• Transferrin saturation — the percentage that helps to assess iron status more precisely
• Haemoglobin test — a reduced value in a full blood count is one of the reasons transferrin is tested