At a glance

Also known as

Iron indices; iron tests

Why get tested?

To evaluate your body's current store of iron

When to get tested?

When your doctor suspects that you may have too little or too much iron in your system

Sample required?

A blood sample drawn from a vein in your arm

Test preparation needed?

Your doctor may request that you fast for 12 hours prior to some iron tests; in this case, only water is permitted.

What is being tested?

Iron is needed to help form adequate numbers of normal red blood cells, which carry oxygen throughout the body. Iron is a critical part of haemoglobin, the protein in red blood cells that binds oxygen in the lungs and releases it as blood travels to other parts of the body. Iron is also needed by other cells, especially muscle (which contains another oxygen binding protein called myoglobin). Low iron levels can lead to anaemia, in which the body does not have enough red blood cells. Other conditions can cause you to have too much iron in your blood.

Evaluation of iron status can include several tests that are not always run together. These include:

  • Serum iron - measures the level of iron in the liquid part of your blood.
  • Ferritin - measures the amount of stored iron in your body. Ferritin is the main protein that stores iron, especially in the liver and the bone marrow (the inside cavity in bones, where blood cells are made).
  • Transferrin or total iron binding capacity (TIBC) - A laboratory usually measures one of either transferrin or TIBC. Transferrin is the main transport protein of iron. TIBC is a good indirect measurement of transferrin. Your body makes transferrin in relationship to your need for iron; when iron stores are low, transferrin levels increase, while transferrin is low when there is too much iron. Usually about one third of the transferrin is being used to transport iron. Because of this, your blood serum has considerable extra iron-binding capacity, which is the unsaturated iron binding capacity (UIBC). The TIBC equals UIBC plus the serum iron measurement. Few laboratories measure UIBC.
  • Transferrin saturation: this is a calculation that represents the percentage of transferrin that is saturated with iron. It is a calculation using either the transferrin or TIBC value, when the serum iron concentration is known.

These tests are often requested together, and the relative changes in each can help your doctor determine the cause of an abnormal result in one or more of these tests.

Several other tests can also be used to help recognise problems with iron in the body.

  • Haemoglobin and PCV - while not really tests of iron status alone, they are widely used parts of the full blood count (FBC) that can detect anaemia; iron deficiency is a common cause of anaemia. Another part of the FBC is the mean (average) cell volume (MCV), which measures how big the red blood cells are. In iron deficiency (and in some other diseases as well), not enough haemoglobin is made, causing the red blood cells to be smaller than normal (microcytic) and paler than normal (hypochromic).
  • HFE gene test – the most common genetic disease in people whose ancestors came from northern Europe is haemochromatosis, a disease that causes your body to absorb too much iron. It is due to an inherited abnormality in a specific gene, called the HFE gene, that regulates the amount of iron absorbed from the gut. In people who have two copies of an abnormal form of the gene, the protein made by the gene cannot tell the cells in the gut when the body is ‘full’ of iron, so the gut keeps on absorbing iron and excess iron damages many different organs. The HFE gene test uses a sample of blood drawn from your arm to see if you have the mutations that cause the disease (the most common is called C282Y).
  • Zinc protoporphyrin – protoporphyrin is the part of haemoglobin that needs iron to help it carry oxygen. If there is not enough iron, another metal (such as zinc) will attach to the protoporphyrin instead. This test, which is simple to do using only a small amount of blood, is sometimes used as a screening test for iron deficiency, especially in children. Because lead prevents iron (but not zinc) from attaching to protoporphyrin, zinc protoporphyrin will also be high in severe cases of lead poisoning.
How is the sample collected for testing?

A blood sample is drawn by needle from a vein in your arm.

Is any test preparation needed to ensure the quality of the sample?

Your doctor may request that you fast for 12 hours prior to some iron tests. In this case, only water is permitted.

The Test

How is it used?

Iron status may be evaluated by ordering one or more tests to determine the amount of iron in the blood, the capacity of the blood to transport iron, and the amount of iron in storage. They may also help differentiate various causes of anaemia.

When is it requested?

Iron studies are requested in two main situations; the investigation of the cause of anaemia and when iron excess is suspected.

Anaemia

This term refers to the presence of too few red blood cells, which are needed to carry oxygen to the body. Many conditions can cause anaemia, but iron deficiency is one of the most common. Normal iron levels are maintained by a balance between the amount of iron taken into the body and the amount of iron lost. Normally, we lose a small amount of iron each day, so if we take in too little iron, deficiency could develop. Unless a person follows a very poor diet, however, there is usually enough iron to prevent iron deficiency in healthy people.

In certain situations there is an increased need for iron. Persons with chronic bleeding from the gut (usually from ulcers or tumours), or women with heavy menstrual periods will lose more iron than normal and often develop iron deficiency. Women who are pregnant or breast feeding lose iron to their baby, and can develop iron deficiency if not enough extra iron is taken. Children, especially during times of rapid growth, need extra iron and can develop iron deficiency.

Anaemia can also occur in states where the body cannot use iron properly. In many chronic diseases, especially in cancers, autoimmune diseases, and with chronic infections (including AIDS), the body cannot use iron properly to make red cells. As a result, production of transferrin decreases, serum iron is low (because little iron is being absorbed from the gut), and ferritin (the storage form of iron) increases.

Iron deficiency occurs with varying degrees of severity. The mildest stage is iron depletion, which means the amount of functioning iron in your body is all right, but the body does not have any extra iron stores. Serum iron is usually normal in this stage. As iron deficiency worsens, iron-deficient erythropoiesis (formation of red blood cells) develops; all of your stored iron is gone and your body begins to produce more transferrin to increase iron transport. As this stage progresses, red cells are produced in normal numbers but they have less haemoglobin than normal (microcytic and hypochromic red cells).

In iron-deficiency anaemia, the most severe form of iron deficiency, the number of red cells produced is low, anaemia develops, serum iron is low, ferritin is low, and transferrin and TIBC are high.

Excess iron

Too much iron can lead to damage to a number of organs, including the heart, liver, pancreas (where insulin is made) and joints most commonly. The most common cause of iron excess is an inherited disease called haemochromatosis. In this disease, the body absorbs more iron than it needs from the gut, and the excess iron gradually accumulates, causing organ damage over many years. The disease is inherited when you get one copy of an abnormal form of the HFE gene from each of your parents (who show no evidence of the disease).

Many people who have haemochromatosis will have no symptoms for their whole life, while others start to develop symptoms such as joint pain, abdominal pain, and weakness in their 20’s or 30’s. Heavy alcohol consumption seems to increase the amount of iron absorbed, while women are somewhat protected because they lose iron every month with their menstrual period.

There is now a test to detect the abnormal form of the gene; this can be used if you have unexplained high iron levels or if you have a family history of haemochromatosis.

Iron poisoning occurs if a large amount of iron is taken all at once. While this is rare, it most commonly occurs in children who get hold of their mother's iron supplements or a bottle of vitamins with iron. If severe enough, iron poisoning can cause death, so it is a good idea to keep all iron supplements well out of the reach of children.

What does the test result mean?

Looking for reference ranges?

A summary of the changes in iron tests seen in various diseases of iron status is shown in the table below.
 

Disease Iron TIBC/Transferrin UIBC %Transferrin
 saturation
Ferritin
Iron deficiency Low High High Low Low
Haemochromatosis High Low Low High High
Chronic illness Low Low Low / normal Low Normal / high
Haemolytic anaemia High Normal / low Low / normal High High
Sideroblastic anaemia Normal / high Normal / low Low / normal High High
Iron poisoning High Normal Low High Normal

Common Questions

Is iron deficiency the same thing as anaemia? What are the symptoms?

Iron deficiency refers to a decrease in the amount of iron stored in the body, while anaemia refers to a drop in the number of red blood cells (RBCs) and/or the amount of haemoglobin within the RBCs. It typically takes several weeks after iron stores are depleted for the level of haemoglobin and production of RBCs to be affected and for anaemia to develop. There usually are few symptoms early in iron deficiency, but as the condition worsens and blood levels of haemoglobin and RBCs decrease, then ongoing weakness and fatigue can develop.

As your iron continues to be depleted, you may have shortness of breath and dizziness. If the anaemia is severe, chest pain, headaches, and leg pains may occur. Children may develop learning (cognitive) disabilities. Besides the general symptoms of anaemia, there are certain symptoms that are characteristic of iron deficiency. These include pica (cravings for specific substances, such as licorice, chalk, dirt, or clay), a burning sensation in the tongue or a smooth tongue, sores at the corners of the mouth, and spoon-shaped finger- and toe-nails.

What are some causes of anaemia besides iron-deficiency?

There are many different conditions that can cause anaemia other than iron deficiency. Some examples include B vitamin deficiency, cancer and genetic disorders such as sickle-cell disease and thalassaemia. However, iron deficiency is the most common cause, which is why iron tests are so frequently performed. If iron tests rule out iron deficiency, another source for the anaemia must be found. See the article on Anaemia for more on these.

What foods contain the most iron?

Haem-iron is the easiest form of iron for the body to absorb. It is found in meats and eggs. Non-haem iron is found in a wide variety of plants and in iron supplements. Iron-rich sources include: green leafy vegetables, (such as spinach, collard greens and kale), wheat germ, whole grain breads and cereals, raisins, and molasses. If you have been diagnosed with iron deficiency anaemia or you are pregnant or breast feeding, vitamin pills or tablets may be needed to provide extra iron. Ask your doctor about the right supplement for you.

Who needs iron supplements?

The people who typically need iron supplements are pregnant women and patients with documented iron deficiency. People should not take iron supplements before talking to their doctor as excess iron can cause chronic iron overload. An overdose of iron pills can be toxic, especially to children.

Last Review Date: December 8, 2013