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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.

Why get tested?

Iron is an essential mineral that is needed by the body to form haemoglobin.  Haemoglobin is the protein in red blood cells that binds oxygen in the lungs and releases it as blood travels to other parts of the body.

The serum iron test measures the amount of iron in the liquid part of your blood.

If your doctor thinks you may have too little – iron deficiency – or too much iron – iron overload/haemochromatosis – they will order serum iron as part of the iron studies group of tests.

They may first request a full blood count (FBC) which provides information about the size and shape of red bloods calls and shows how much haemoglobin is in your blood.  

If your full blood count is abnormal, they will request iron studies to investigate further.  Sometimes, a doctor may measure iron studies and an FBC at the same time.

Having the test


Serum iron is measured on a blood sample, usually taken from a vein in the arm.


Any preparation?


Your results

Reading your test report

Your results will be presented along with those of your other tests on the same form.  You will see separate columns or lines for each of these tests.

Iron deficiency anaemia comes on gradually. When the rate of iron loss is more than 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 transferrin may be 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 serum iron level varies throughout the day and is influenced by any food or drink you have recently taken.  The serum iron result will not be interpreted on its own, but rather your doctor will consider all the tests in the iron studies panel as a whole and use this information to decide whether it is likely that you have iron deficiency or iron excess.

It is not possible to interpret serum iron levels if you have recently had an intravenous iron infusion.  Similarly, taking iron supplements could affect how your serum iron result is interpreted – you should tell your doctor if this is the case.


Summary of the changes in iron test results seen in various disorders.




TIBC or Transferrin

Percentage of transferrin saturation

Iron deficiency










Chronic illness





Haemolytic anaemia





Sideroblastic anaemia


Normal/ High

Normal/ Low


Iron poisoning






Reference intervals

Your results will be compared to reference intervals (sometimes called a normal range). 

  • Reference intervals are the range of results expected in most healthy people of the same age and sex. 
  • Your results may be flagged high or low if they sit outside this range.
  • Many reference intervals vary between labs so only those that are standardised or harmonised across most laboratories are given on this website.

If your results are flagged as high or low this does not necessarily mean that anything is wrong. Blood test results must be interpreted with an understanding of your own particular symptoms and clinical situation.  For this reason, your results are best interpreted by your own doctor.

Questions to ask your doctor

The choice of tests your doctor makes will be based on your medical history and symptoms.   It is important that you tell them everything you think might help.

You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.

Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:

  • Why does this test need to be done?
  • Do I need to prepare (such as fast or avoid medications) for the sample collection?
  • Will an abnormal result mean I need further tests?
  • How will the results from this test change the course of my care?
  • What will happen next, after the test?

More information

Pathology and diagnostic imaging reports can be added to your My Health Record. You and your healthcare provider can now access your results whenever and wherever needed.

Get further trustworthy health information and advice from healthdirect.

Last Updated: Thursday, 1st June 2023

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