A ferritin blood test helps doctors evaluate the amount of iron stored in the body. The body uses iron to make hemoglobin, the oxygen-carrying protein inside red blood cells.
Iron is obtained from food and stored for use as ferritin, an iron-carrying protein. Ferritin is found mostly in the liver, but it's also present in smaller amounts in the bone marrow, spleen, and muscles. Only a small amount is normally present in the blood, but it can still be used to estimate the body's total iron stores.
Stored iron is important because when iron intake is low, the body relies on ferritin to release the iron it needs. If enough iron isn't available in storage, a person will progress through several stages of iron deficiency. If the situation isn't corrected, iron deficiency may eventually lead to anemia — a decreased amount of hemoglobin in the blood, resulting in difficulty delivering oxygen to the cells and tissues.
Most iron deficiency cases in childhood are due to low iron intake — for example, getting too few iron-rich foods such as red meat and fortified cereals, or, in bottle-fed infants, switching from iron-fortified formula to cow's milk before 12 months. Infants who are breastfed tend to get enough iron from their mothers until about 4-6 months of age, when iron-fortified cereal is usually introduced.
Low iron also may be caused by poor iron absorption by the intestine or by blood loss, most commonly from heavy menstruation or gradual blood loss in the intestinal tract.
Some health conditions can result in too much iron and ferritin in the body (iron overload). The most common is hemochromatosis, a genetic disease in which too much iron is absorbed.
Why It's Done
Doctors may order ferritin test when they suspect kids have too little or too much iron in their bodies. This suspicion is often based on the results of routine blood tests, such as a complete blood counts, that show low hemoglobin levels.
Other times, doctors may suspect problems with iron levels based on certain symptoms. Early symptoms if iron depletion or deficiency might be subtle. But once levels drop below a certain amount, kids might experience symptoms such as fatigue, weakness, pale skin, rapid heartbeat, or dizziness. The most common symptoms of iron overload are joint pain, chronic fatigue, and abdominal pain.
Ferritin levels are a helpful first indicator of abnormal iron stores because they tend to drop or rise even before symptoms occur. They are also not as prone to dietary fluctuations as blood iron levels.
No special preparations are needed for this test. On the day of the test, it may help to have your child wear a short-sleeve shirt to allow easier access for the technician who will be drawing the blood.
A health professional will usually draw the blood from a vein. For an infant, the blood may be obtained by puncturing the heel with a small needle (lancet). If the blood is being drawn from a vein, the skin surface is cleaned with antiseptic and an elastic band (tourniquet) is placed around the upper arm to apply pressure and cause the veins to swell with blood. A needle is inserted into a vein (usually in the arm inside of the elbow or on the back of the hand) and blood is withdrawn and collected in a vial or syringe.
After the procedure, the elastic band is removed. Once the blood has been collected, the needle is removed and the area is covered with cotton or a bandage to stop the bleeding. Collecting the blood for the test will only take a few minutes.
Either method (heel or vein withdrawal) of collecting a blood sample is only temporarily uncomfortable and can feel like a quick pinprick. Afterward, there may be some mild bruising, which should go away in a day or so.
Getting the Results
The blood sample will be processed by a machine. The results are commonly available within 1-2 days.
The ferritin test is considered a safe procedure. However, as with many medical tests, some problems can occur with having blood drawn:
fainting or feeling lightheaded
hematoma (blood accumulating under the skin causing a lump or bruise)
pain associated with multiple punctures to locate a vein
Helping Your Child
Having a blood test is relatively painless. Still, many children are afraid of needles. Explaining the test in terms your child can understand might help ease some of the fear.
Allow your child to ask the technician any questions he or she might have. Tell your child to try to relax and stay still during the procedure, as tensing muscles and moving can make it harder and more painful to draw blood. It also may help for your child to look away when the needle is being inserted into the skin.
If You Have Questions
If you have questions about the ferritin test, speak with your doctor. You can also talk to the technician before the procedure.