The Test Sample
What is being tested?
Ferritin is an iron-containing protein and is the primary form of iron stored inside of cells. The small quantity of ferritin that is released into the blood is a reflection of the amount of total iron stored in the body. This test measures the amount of ferritin in the blood.
In healthy people, about 70% of the iron absorbed by the body is incorporated into the hemoglobin of red blood cells. Most of the remaining 30% is stored as ferritin or as hemosiderin, a complex of iron, proteins, and other materials. Ferritin and hemosiderin are present primarily in the liver but also in the bone marrow, spleen, and skeletal muscles.
When available iron is insufficient to meet the body's needs, iron stores are depleted and ferritin levels decrease. This may occur because of insufficient iron intake, inadequate absorption, or increased need for iron such as during pregnancy or due to a condition that causes chronic blood loss. Significant depletion of iron stores may occur before any signs of iron deficiency develop.
Iron storage and ferritin levels increase when more iron is absorbed than the body needs. Chronic absorption of excess iron will lead to the progressive buildup of iron compounds in organs and may eventually cause their dysfunction and failure. This happens in hemochromatosis, a genetic disease in which the body absorbs too much iron, even on a normal diet.
How is the sample collected for testing?
A blood sample is drawn by needle from a vein in the 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?
A 12-hour fast may be required. In this case, only water is permitted. Morning specimens are preferred.