This test measures the amount of iron in the liquid portion of your blood and is one of a group or panel of blood tests that collectively looks at how much iron is in your blood and body. Your doctor may request iron studies if you have symptoms of having too little or too much iron. 

The iron studies panel is made up of several tests, most commonly:
- Ferritin
- Serum iron
- Transferrin
- Transferrin saturation or
- Total iron binding capacity (TIBC)

Iron levels in your blood vary markedly throughout the day, which means that measuring iron alone is rarely useful in making a diagnosis. However, knowing your iron level is important in calculating transferrin saturation. Transferrin is a protein that moves iron throughout the body. A transferrin saturation test shows how much iron is bound to transferrin. A low transferrin saturation usually suggests iron deficiency while a high saturation often confirms iron overload or haemochromatosis.

What is being tested?

Iron is an essential trace element in your blood. It is necessary for forming healthy red blood cells, which carry oxygen through your body, and for some enzymes, which perform tasks in your body.

If anaemia is suspected the first test required is a full blood examination. This provides information about the amount of haemoglobin (low in anaemia), size of the red blood cells (small in iron deficiency anaemia and some other conditions) and other useful measures to provide clues about the cause of the anaemia. If iron deficiency is suggested from the full blood examination, then iron studies will be performed. Iron studies include iron, ferritin, transferrin and transferrin saturation. Sometimes the specialised test, soluble transferrin receptor may be requested.
 

How is it used?

The iron test is used to measure the amount of iron that is carried by transferrin, a protein that transports iron from the gut to cells that use iron. In people with anaemia, iron studies (iron, ferritin, transferrin and transferrin saturation) can help to tell whether it is due to iron deficiency. It can also help to identify when anaemia is due to a long-term (chronic) illness.

Iron studies can also be used to help diagnose hereditary haemochromatosis, a condition where too much iron builds up in the body.

In both these situations the level of ferritin is the most useful single test to determine deficiency or overload.

When is it requested?

Iron studies are not requested routinely. If haemoglobin and haematocrit are abnormal, however, iron studies and in particular the ferritin level can be useful in determining the cause of anaemia. The ferritin level can also be used when iron deficiency is being treated to tell if the iron is being absorbed properly and to detect when enough iron has been taken. The test also may be requested when your doctor suspects you may have too much iron. If you have symptoms that could be due to haemochromatosis, iron tests represent the best way to determine whether this could be the diagnosis.

In a child who has accidently taken an overdose of iron tablets, iron levels in the first 4 hours after the tablets have been taken along with a thorough medical assessment and emergency blood tests can help determine the severity of poisoning.

What does the result mean?

The serum iron level varies markedly throughout the day and according to recent intake - it is not helpful and should not be used alone in the diagnosis of iron deficiency anaemia.

A low ferritin level is usually due to iron deficiency, especially if transferrin or TIBC is high. With chronic (long-term) diseases, low, normal or high ferritin can occur with low transferrin or TIBC.

High levels of ferritin can occur as the result of many blood transfusions, iron injections into muscle, lead poisoning, liver disease, or kidney disease. Haemochromatosis is the most common cause of high iron.

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

Common questions

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

Iron-deficiency anaemia is the most severe form of iron deficiency. Relatively mild iron deficiency, which may cause no effects at all, is referred to as ‘iron depletion’. If a person is otherwise healthy, symptoms seldom appear before the haemoglobin in your blood drops below a certain level (100g per litre). Some signs that your body is low in iron include tiredness and heart palpitations.
As iron levels continue to fall, symptoms can include:

• Shortness of breath and dizziness
• If the anaemia is severe, angina (chest pain), headache and leg pains may occur
• Children may have learning (cognitive) disabilities
• Besides the general symptoms of anaemia, there can be certain symptoms if you have had a long-term case of iron deficiency. These can include a burning sensation in the tongue or a smooth tongue, sores at the corners of the mouth, pica (cravings for specific substances, such as liquorice, chalk, or clay), and spoon-shaped finger- and toe-nails.

• Does anaemia due to iron deficiency happen quickly or does it take a long time?

Iron deficiency anaemia comes on gradually. When your rate of iron loss exceeds the amount of iron you absorb from your diet, the first thing that occurs is that iron stores are used up. In this stage, ferritin will be low, but iron and TIBC are usually normal and there is no anaemia. As iron deficiency worsens, blood iron levels fall, TIBC and transferrin rise, and red blood cells may start to become small and pale, but there is still an adequate number of red blood cells. With prolonged or severe iron deficiency, anaemia develops.

• What are signs of iron overload in my system?

The most common symptom is pain, as iron accumulates in your body, usually in your joints. Other symptoms include fatigue and lack of energy, abdominal pain, loss of sex drive, and heart problems. Some people, however, have no symptoms of this condition.

• What foods contain the most iron?

If laboratory tests show that you are anaemic, eating the right diet can help. Some good choices for an iron-rich diet include: lean meats, liver, eggs, green leafy vegetables (e.g. spinach, kale), wheat germ, whole grain breads and cereals, raisins and molasses. If you have been diagnosed as having iron deficiency anaemia, or you are pregnant or breast feeding, iron in the form of vitamin pills or tablets is usually needed to provide the extra iron needed in these states.

• My friend told me I can take too much iron—is that right?

Unless you have iron deficiency or eat a very poor diet, you probably don't need extra iron supplements. If you take in much more iron than is recommended, you may develop haemosiderosis, which causes a rise in blood iron and ferritin levels. If you have an inherited disorder called haemochromatosis, taking extra iron can cause more rapid iron accumulation and possibly accelerate the rate of damage to your organs.

• My doctor instructed me to take my iron supplement and then have an iron test done. Why would that be?

Your doctor may suspect that you are not absorbing the iron you need from your supplements and your diet, so she or he may ask that you have your ferritin level checked shortly after you take your iron supplement. If you take iron and then have an abnormally low ferritin test result, you may have an underlying condition affecting the absorption of iron. You may need to be treated for the condition causing the malabsorption for your iron stores to return to normal.

More information

RCPA Manual: Iron

Healthdirect Australia: Iron