What Is a Ferritin Test?

A ferritin test is a blood test that measures the concentration of a protein called ferritin in the blood. This carrier protein typically stores iron. The test is often done as part of an investigation into why a patient has anemia, or low red blood cell counts, because iron deficiency causes anemia and is associated with low ferritin levels. Just as having low levels signals the presence of underlying disease, high levels can also be associated with different pathologic processes. Diseases such as hemochromatosis, leukemia, lymphoma, acute bacterial infection, and chronic inflammatory conditions are associated with high ferritin levels.

The function of ferritin in the body is to bind to iron and store it for future use. A measurement of the concentration of ferritin in the blood is a reflection of the body's total iron stores. High levels suggest that the body has excess iron, whereas low levels suggest an iron deficiency. Normal levels for the ferritin test range from approximately 20-500 nanograms per milliliter (ng/mL) for men and 20-200 ng/mL for women.

Iron deficiency is the most important reason for having low levels on the ferritin test. In this case, ferritin is low because the body doesn’t have much iron to store. Patients with iron deficiency often have anemia because iron is an important component of these blood cells. They can have symptoms like fatigue, fast heart rate, shortness of breath, and pica, which is a craving for dirt or other non-nutritive substances.

As low ferritin levels correlate to low iron stores, high ferritin levels are associated with high iron stores. Hemochromatosis is a disease that causes drastic elevations in ferritin. Patients with this genetic disease are not able to remove iron from their bodies, and throughout their lifetime build up more and more iron. When they reach middle age, this iron excess can cause diabetes, problems with liver function, and a brown discoloration of the skin. Patients who receive many blood transfusions over the courses of their lives, for example those with a condition called thalassemia, can also have excess iron stores.

Sometimes patients with certain cancers will have high levels on a ferritin test. Malignancies such as leukemia and lymphoma can be associated with high levels of this carrier protein. In this case, levels of ferritin are high because the abnormal cancer cells can produce this protein.

Many times elevated levels in the ferritin test can signal the presence of inflammation in the body. The protein is considered an acute phase reactant, which means that its levels rise when the body is fighting off a stressor. Some researchers suggest that ferritin levels rise when patients are trying to fight off bacteria to keep them from using the body's iron for their own use. Chronic inflammatory conditions, such as rheumatoid arthritis, are also associated with elevations in ferritin levels.