Ferritin is a protein that stores iron, mainly in the liver, releasing it when it is needed. Iron is used to make haemoglobin, the protein in red blood cells that gives them their colour, and which carries oxygen through the bloodstream. The amount of ferritin that is circulating in your blood reflects the total amount of iron stored in your body. A ferritin test can be requested by itself but it is also ordered as part of a group of tests known as iron studies which includes other tests relating to the body's iron levels.
What is being tested?
Iron is an integral part of haemoglobin, the red protein that carries oxygen in the blood. An inadequate supply of iron is one cause of a fall in haemoglobin or anaemia.
Iron is mainly stored in the protein ferritin, but also in another protein called haemosiderin. Ferritin and haemosiderin are present mostly in the liver, but also in the bone marrow, spleen and muscles. In healthy people, most iron is stored in ferritin (an estimated 70% in men and 80% in women) and smaller amounts are stored in haemosiderin. Small amounts of ferritin also circulate in the blood. The ferritin concentration within the blood stream reflects the amount of iron stored in your body.
Inadequate dietary iron or increased demand as in pregnancy or malabsorption or blood loss over a long period (e.g. excessive menses or with haemorrhoids) may lead to depletion of iron stores and anaemia.
How is it used?
The ferritin test is requested to see how much iron your body has stored. The test is done, usually with an iron test and the total iron binding capacity (TIBC), unbound iron binding capacity (UIBC), or transferrin saturation, to learn about iron levels in your blood. It is the most useful indicator of iron deficiency.
When is it requested?
It is commonly requested when a doctor thinks a patient has too little iron in their body. If a blood count indicates that your haemoglobin and haematocrit are low, especially if your red blood cells are smaller and paler than normal ('microcytic' and 'hypochromic'), this indicates that you have anaemia due to iron deficiency. Ferritin and other iron tests can be used to confirm the diagnosis.
The test may also be requested when your doctor suspects you have too much iron, for example in haemochromatosis (a disease in which too much iron is absorbed from the diet).
What does the result mean?
Ferritin levels are low in iron deficiency, falling before the haemoglobin starts falling.
Ferritin levels are high in states of long-term iron overload, especially in haemochromatosis. However ferritin is also raised in inflammatory states so that its interpretation becomes very difficult in many situations : e.g. rheumatoid arthritis, chronic kidney disease or inflammatory bowel disease or even malignancy.
A summary of the changes in iron tests seen in various diseases of iron status is shown in the table below.
Condition | Ferritin | Iron | TIBC or Transferrin | Percentage of transferrin saturation |
Iron deficiency | Low | Low | High | Low |
Haemochromatosis | High | High | Low | High |
Chronic illness | Normal/high | Low | Low | Low |
Haemolytic anaemia | High | High | Normal/Low | High |
Sideroblastic anaemia | High | Normal/ High | Normal/ Low | High |
Iron poisoning | Normal | High | Normal | High |
Is there anything else I should know?
Ferritin is normally found mainly inside of the cells in the body, with only a small amount in the blood. When there is damage to organs that contain ferritin and in inflammatory states, ferritin levels can become raised even though the total amount of iron in the body is normal. Ferritin levels may not be particularly helpful if measured in people with liver disease, long-term infections, cancer or autoimmune diseases.
Common questions
Iron deficiency refers to a decrease in the amount of iron stored in the body, while anaemia refers to a drop in the number of red blood cells (RBC) and/or the amount of haemoglobin within the RBC. 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). The commonest sign that your body is low in iron iis fatigue.
As iron levels continue to fall, symptoms may include:
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, UIBC 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.
Many people have no symptoms of this condition in spite of significant iron over load. The most common symptom is joint pain, as iron accumulates in your body. Other symptoms include tiredness and lack of energy, abdominal pain (pain around the stomach area), symptoms of diabetes and loss of sex drive.
Iron-rich sources include: lean meats, liver, eggs, green leafy vegetables (e.g. spinach), wheat germ, whole grain breads, cereals and raisins. However, the amount of iron that is absorbed in the gut can be altered by other substances e.g.: Vitamin C in your diet which increases absorption. 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 required in these states. Talk to your doctor about the right supplement for you.
The body controls entry of iron into the body via the intestine but there is no controlled exit from the body. 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, where there is failure of control of absorption in the intestine, 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 iron level checked shortly after you take your iron supplement. If you take iron and then have an abnormally low 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 levels to return to normal.
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