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.

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 ferrtin 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.

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.

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

About Reference Intervals

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.

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.

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.

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.

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.

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.