At a Glance
Why Get Tested?
To find out whether the amount of iron in your blood is normal.
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.
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.
The Test Sample
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.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
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.
Ask a Laboratory Scientist
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.