Ferritin is a protein which serves as a storage center for iron. It is found in many tissues but the highest concentrations are in the liver, spleen and bone marrow.
The total body iron stores in normal people correlate well with the concentration of ferritin in serum. If there is a deficiency in iron, that is the concentration of iron is low in the blood, the ferritin result will be decreased. Likewise, an overload of iron indicates an increase in the level of ferritin. However, in some conditions like liver disease ferritin will be elevated.