Also Known As
Serum iron
Formal Name
This article was last reviewed on
This article waslast modified on 3 December 2017.
At a Glance
When To Get Tested?

Serum iron blood tests are not performed routinely. Most often, serum iron levels are tested if your doctor thinks that you might have too much iron in your blood. A high iron level can be due to a genetic condition, extensive blood transfusions, or rarely due to ingestion of an overdose of iron (usually in children).

Previously, serum iron was also commonly requested when iron deficiency was suspected. However, it is now recommended that the amount of stored iron (in the form of ferritin) rather than serum iron is measured to aid diagnosis of iron deficiency anaemia. Ferritin analysis gives a measure of body iron stores and is a better indicator of iron deficiency than measuring the iron in blood. However, serum iron blood tests can help to identify when anaemia is due to a long-term (chronic) illness.

Why Get Tested?

To find out whether the amount of iron in your blood is normal.

Sample Required?

A blood sample taken from a vein in your arm

Test Preparation Needed?

Samples for iron should be taken in the morning after 12 hours without any food or drink (except water). You should not take any iron supplements for at least 24 hours prior to the test.

On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you will be able to access your results online.

If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.

Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.

Reference ranges are dependent on many factors, including patient age, gender, sample population, and test method, and numeric test results can have different meanings in different laboratories.

For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.

For more information on reference ranges, please read Reference Ranges and What They Mean.

What is being tested?

The iron test measures the amount of iron that is circulating in the liquid part of blood bound to transferrin (a transport protein). Iron is an essential trace element in your blood. It is necessary for forming healthy red blood cells. Approximately 70% of iron absorbed from the diet is used to form haemoglobin, the protein within red blood cells which carries oxygen through your body. Iron is also used in the production of some other proteins, such as myoglobin in muscle, and various enzymes. Iron which is not used for protein production is stored within tissues as ferritin or haemosiderin.

If not enough iron is taken in from the diet, then the stored levels of iron will drop. If the stored levels become depleted, this can lead to iron deficiency anaemia. On the other hand, absorption of too much iron can cause accumulation of iron stores in the tissues. This can cause damage to organs such as the heart, liver, and pancreas.

How is the sample collected for testing?

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

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

Samples for iron should be taken in the morning, before you have had any food to eat. You should not take any iron tablets for 24 hours before the test. Iron is absorbed rapidly from food or tablets, and can make your blood iron levels falsely high.

Accordion Title
Common Questions
  • 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 intestine to cells that use iron. The amount of iron within the blood varies throughout the day, and from one day to the next.  An iron blood (serum) test is therefore not a useful measure of iron status if it is used on its own. Serum iron is therefore often requested in combination with other tests of iron status. Such tests include transferrin, ferritin, TIBC (total iron binding capacity) and UIBC (unbound iron binding capacity).

    Iron tests are requested if a doctor suspects iron poisoning, or conditions of excessive iron storage. Excessive iron storage can occur as a result of a genetic condition called hereditary haemochromatosis, however, it can also occur following multiple blood transfusions. If iron overload is suspected, both iron and transferrin concentrations are measured. Transferrin saturation can then be calculated to determine the extent of the iron overload. Transferrin saturation reflects the amount of iron being transported within the blood, and its capacity to carry more.

    Iron blood tests are no longer commonly used when iron deficiency is suspected. This is because ferritin analysis provides a more reliable indicator of iron deficiency as its concentration reflects the level of iron stores. However, a serum iron test may be useful to help to identify when anaemia is due to a long-term (chronic) illness.

  • When is it requested?

    Iron tests are not requested routinely. The test may be requested when your doctor suspects you may have too much iron. Iron tests are less commonly used in conditions of iron deficiency. If you have symptoms that could be due to iron overload (haemochromatosis), iron analysis in combination with calculation of transferrin saturation represents the best way to determine whether this could be the diagnosis. In a child who has taken iron tablets, iron levels are the only way to measure the severity of poisoning.

    If a doctor suspects you have too little iron, then a ferritin blood test is normally requested to determine the extent of the iron stores in the body. If ferritin levels are normal but the doctor still suspects iron deficiency anaemia, then iron analysis is useful to aid the diagnosis.

  • What does the test result mean?

    High levels of serum iron can occur as the result of many blood transfusions, iron injections into muscle, lead poisoning, liver disease, or kidney disease. Hereditary haemochromatosis is the most common cause of high iron concentrations in the blood. High iron levels may also be caused by ingestion of large amounts of iron. This is most often seen in people who have taken excessive iron supplements, either intentionally or accidently.

    A low iron concentration in the blood is usually due to iron deficiency, especially if transferrin or TIBC is high. With chronic (long-term) diseases, low iron occurs with low transferrin or TIBC.

  • Is there anything else I should know?

    Samples for iron should be taken in the morning, before you have had any food to eat. You should not take any iron pills or tablets for 24 hours before the test. Iron is absorbed rapidly from food or pills, and can make your blood iron levels falsely high.

    Substances that can cause high iron levels include the contraceptive pill, oestrogen pills and preparations, iron supplements, heavy intake of alcoholic drinks, methyldopa, and chloramphenicol.

    Substances that can cause your iron level to be decreased include ACTH (a hormone), the drugs colchicine, desferrioxamine, methicillin, and testosterone.

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

    Iron-deficiency anaemia is the most severe form of iron deficiency (low iron levels). 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), iron-fortified breads, raisins, nuts and apricots. However, the amount of iron that is absorbed in the gut can also be altered by other substances in your diet, such as Vitamin C. 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. It is important to speak to your doctor before starting any form of supplements.

  • 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 iron overload, which causes a rise in blood iron and ferritin levels. If you have an inherited disorder called hereditary haemochromatosis, taking extra iron can cause more rapid iron accumulation and possibly accelerate the rate of damage to your organs.