To determine your body's total iron storage capacity; to help diagnose iron deficiency or iron overload
When you have low hemoglobin and hematocrit on a complete blood count (CBC); when your healthcare practitioner suspects that you may have too little iron (iron deficiency) or too much iron (iron overload) in the body
A blood sample drawn from a vein in your arm
You may be instructed to have your blood drawn in the morning and/or fast for 12 hours before the test; in this case, only water is permitted. Follow any instructions from your healthcare practitioner and/or from the laboratory performing the test.
Ferritin is a protein that contains iron and is the primary form of iron stored inside of cells. The small amount of ferritin that is released and circulates in the blood is a reflection of the total amount of iron stored in the body. This test measures the amount of ferritin in the blood.
Iron is an essential trace element and nutrient that, among other functions, is necessary for the production of healthy red blood cells (RBCs). The body cannot produce iron and must absorb it from the foods we eat or from supplements.
In healthy people, most of the iron absorbed by the body is incorporated into the hemoglobin of red blood cells. Most of the remaining is stored as ferritin or as hemosiderin, with additional small amounts used to produce other proteins such as myoglobin and some enzymes. Ferritin and hemosiderin are present primarily in the liver but also in the bone marrow, spleen, and skeletal muscles.
When the level of iron is insufficient to meet the body's needs, the level of iron in the blood drops, iron stores are depleted and ferritin levels decrease. This may occur because:
- Not enough iron is consumed (either foods or supplements)
- The body is unable to absorb iron from the foods eaten in conditions such as celiac disease
- There is an increased need for iron such as during pregnancy or childhood, or due to a condition that causes chronic blood loss (e.g., peptic ulcer, colon cancer).
Insufficient levels of circulating and stored iron may eventually lead to iron deficiency anemia (decreased hemoglobin). In the early stage of iron deficiency, no physical effects are usually seen and the amount of iron stored may be significantly depleted before any signs or symptoms of iron deficiency develop. If a person is otherwise healthy and anemia develops over a long period of time, symptoms seldom appear before the hemoglobin in the blood drops below the lower limit of normal.
However, as the iron-deficiency progresses, symptoms eventually begin to appear. The most common symptoms of iron deficiency anemia include fatigue, weakness, dizziness, headaches and pale skin. (Read the article on Anemia to learn more.)
Conversely, iron storage and ferritin levels increase when more iron is absorbed than the body needs. Absorbing too much iron over time can lead to the progressive buildup of iron compounds in organs and may eventually cause their dysfunction and failure. An example of this is hemochromatosis, a rare genetic disease in which the body absorbs too much iron, even on a normal diet. Additionally, iron overload can occur when a person undergoes repeated blood transfusions.
How is the test used?
The ferritin test is used to assess a person's iron stores in the body. The test is often ordered along with an iron level and total iron-binding capacity (TIBC, calculated based on blood level of transferrin) to detect a low iron level (iron deficiency) or too much iron in the body (iron overload) as well as to assess the severity of these conditions.
When is it ordered?
The ferritin test may be ordered, along with other iron tests, when a routine complete blood count (CBC) shows that a person's hemoglobin and hematocrit are low and their red blood cells are smaller and paler than normal (microcytic and hypochromic), suggesting iron deficiency anemia even though other clinical symptoms may not have developed yet.
- Chronic fatigue/tiredness
- Pale skin (pallor)
A ferritin level may also be ordered when iron overload is suspected. Signs and symptoms of iron overload will vary from person to person and tend to worsen over time. They are due to iron accumulation in the blood and tissues. They may include:
- Joint pain
- Fatigue, weakness
- Weight loss
- Lack of energy
- Abdominal pain
- Loss of sex drive
- Organ damage, such as in the heart and liver
What does the test result mean?
Ferritin levels are often evaluated in conjunction with other iron tests. A summary of the changes in iron tests seen in various diseases of iron status is shown in the table below.
Disease Iron TIBC/Transferrin UIBC Ferritin Iron Deficiency Low High High Low Low Hemochromatosis/Hemosiderosis High Low Low High High Chronic Illness Low Low/Normal Low/Normal Low/Normal High/Normal Hemolytic Anemia High Normal/Low Low/Normal High High Sideroblastic Anemia Normal/High Normal/Low Low/Normal High High Iron Poisoning High Normal Low High Normal
The early stage of iron deficiency is the slow depletion of iron stores. This means there is still enough iron to make red cells but the stores are being used up without adequate replacement. The serum iron level may be normal in this stage, but the ferritin level will be low.
As iron deficiency continues, all of the stored iron is used and the body tries to compensate by producing more transferrin to increase iron transport. The serum iron level continues to decrease and transferrin and TIBC and UIBC increase. As this stage progresses, fewer and smaller red blood cells are produced, eventually resulting in iron deficiency anemia. Transferrin saturation is decreased with iron deficiency.
If the iron level and transferrin saturation are high, the TIBC, UIBC and ferritin are normal and the person has a clinical history consistent with iron overdose, then it is likely that the person has iron poisoning. Iron poisoning occurs when a large dose of iron is taken all at once or over a short period of time. Iron poisoning in children is almost always acute, occurring in children who ingest their parents' iron supplements. In some cases, acute iron poisoning can be fatal. In patients with chronic iron overload, ferritin levels increase.
A person who has mutations in the HFE gene is diagnosed with hereditary hemochromatosis. However, while many people who have hemochromatosis will have no symptoms for their entire life, others will start to develop symptoms such as joint pain, abdominal pain, and weakness in their 30's or 40's. Men are affected more often than women because women lose blood during their reproductive years through menstruation.
Iron overload may also occur in people who have hemosiderosis and in those who have had repeated transfusions. This may occur with sickle cell anemia, thalassemia major, or other forms of transfusion-dependent anemia. The iron from each transfused unit of blood stays in the body, eventually causing a large buildup in the tissues. Some persons with alcoholism and with chronic liver disease also develop iron overload.
Is there anything else I should know?
Normally, most ferritin is found inside of cells with only a small amount in the blood. Patients with iron overload have high ferritin levels. However, ferritin levels can become elevated under certain condition (e.g., acute illness) even though the total amount of iron in the body is normal.
My iron level is normal, but my ferritin level is low. Why is that?
The development of iron deficiency anemia is a gradual process. If your body is not taking in enough iron, your body first uses the iron that is stored in tissues (i.e., ferritin) and blood levels of ferritin will begin to decrease. If not corrected, the stored iron begins to be depleted as it is used in the production of red blood cells. In the early stages of iron-deficiency, blood levels of iron can be normal while stored iron, and therefore ferritin levels, will begin to decrease.
I know eating foods high in iron or taking iron supplements will increase my iron level, but will it also increase my ferritin level?
What other conditions may alter ferritin levels?
Who should take iron supplements?
The people who typically need iron supplements are pregnant women and those with documented iron deficiency. Young women who become anemic due to poor dietary intake and have chronic and/or excessive loss of blood during their menstrual cycle may require iron supplements. People should not take iron supplements before talking to their healthcare practitioner as excess iron can cause chronic iron overload. An overdose of iron pills can be toxic, especially to children.
Is there any way to cure iron overload?
If it is due to a temporary condition or ingestion of iron supplements, then it will likely resolve on its own once the condition is resolved or supplement ingestion is stopped. If it is due to hemochromatosis or to a chronic disease, then it cannot be cured; careful management by your healthcare practitioner is required. In severe cases, periodic removal of a prescribed amount of blood, also known as therapeutic phlebotomy, may be necessary.