At a Glance
Why Get Tested?
To evaluate your body's current store of iron
When to Get Tested?
When your doctor suspects that you may have too little or too much iron in your system
A blood sample drawn from a vein in your arm
Test Preparation Needed?
Your doctor may request that you fast for 12 hours prior to some iron tests; in this case, only water is permitted.
The Test Sample
What is being tested?
Iron is needed to help form adequate numbers of normal red blood cells, which carry oxygen throughout the body. Iron is a critical part of haemoglobin, the protein in red blood cells that binds oxygen in the lungs and releases it as blood travels to other parts of the body. Iron is also needed by other cells, especially muscle (which contains another oxygen binding protein called myoglobin). Low iron levels can lead to anaemia, in which the body does not have enough red blood cells. Other conditions can cause you to have too much iron in your blood.
Evaluation of iron status can include several tests that are not always run together. These include:
- Serum iron - measures the level of iron in the liquid part of your blood.
- Ferritin - measures the amount of stored iron in your body. Ferritin is the main protein that stores iron, especially in the liver and the bone marrow (the inside cavity in bones, where blood cells are made).
- Transferrin or total iron binding capacity (TIBC) - A laboratory usually measures one of either transferrin or TIBC. Transferrin is the main transport protein of iron. TIBC is a good indirect measurement of transferrin. Your body makes transferrin in relationship to your need for iron; when iron stores are low, transferrin levels increase, while transferrin is low when there is too much iron. Usually about one third of the transferrin is being used to transport iron. Because of this, your blood serum has considerable extra iron-binding capacity, which is the unsaturated iron binding capacity (UIBC). The TIBC equals UIBC plus the serum iron measurement. Few laboratories measure UIBC.
- Transferrin saturation: this is a calculation that represents the percentage of transferrin that is saturated with iron. It is a calculation using either the transferrin or TIBC value, when the serum iron concentration is known.
These tests are often requested together, and the relative changes in each can help your doctor determine the cause of an abnormal result in one or more of these tests.
Several other tests can also be used to help recognise problems with iron in the body.
- Haemoglobin and PCV - while not really tests of iron status alone, they are widely used parts of the full blood count (FBC) that can detect anaemia; iron deficiency is a common cause of anaemia. Another part of the FBC is the mean (average) cell volume (MCV), which measures how big the red blood cells are. In iron deficiency (and in some other diseases as well), not enough haemoglobin is made, causing the red blood cells to be smaller than normal (microcytic) and paler than normal (hypochromic).
- HFE gene test – the most common genetic disease in people whose ancestors came from northern Europe is haemochromatosis, a disease that causes your body to absorb too much iron. It is due to an inherited abnormality in a specific gene, called the HFE gene, that regulates the amount of iron absorbed from the gut. In people who have two copies of an abnormal form of the gene, the protein made by the gene cannot tell the cells in the gut when the body is ‘full’ of iron, so the gut keeps on absorbing iron and excess iron damages many different organs. The HFE gene test uses a sample of blood drawn from your arm to see if you have the mutations that cause the disease (the most common is called C282Y).
- Zinc protoporphyrin – protoporphyrin is the part of haemoglobin that needs iron to help it carry oxygen. If there is not enough iron, another metal (such as zinc) will attach to the protoporphyrin instead. This test, which is simple to do using only a small amount of blood, is sometimes used as a screening test for iron deficiency, especially in children. Because lead prevents iron (but not zinc) from attaching to protoporphyrin, zinc protoporphyrin will also be high in severe cases of lead poisoning.
How is the sample collected for testing?
A blood sample is drawn by needle from a vein in your arm.
Is any test preparation needed to ensure the quality of the sample?
Your doctor may request that you fast for 12 hours prior to some iron tests. In this case, only water is permitted.
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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.