Ferritin is an iron-containing protein that serves as a recyclable form of stored iron in the body. Ferritin levels in the blood are an easily measured indicator of the body's total iron stores. These stores can rise and fall with changes in iron intake and usage, or with certain illnesses.
Blood Ferritin
The concentration of ferritin in the bloodstream at any given time is directly proportional to the body's total amount of storage iron. Ferritin levels decrease as iron stores are depleted, and increase as iron stores rise. MedlinePlus states the normal range for blood ferritin is 12 to 300 ng/mL in men, and 12 to 150 ng/mL in women. Women tend to have lower levels due to regular menstrual blood loss. Normal values may vary between laboratories, depending on the test method and instrumentation used.
Decreased Ferritin Levels
Low ferritin levels essentially always indicate low iron stores and iron deficiency, according to "Clinical Diagnosis and Management by Laboratory Methods." A common cause of iron deficiency in adults is chronic blood loss, as seen with gastrointestinal bleeding or excessive menstruation. Other causes of iron depletion include pregnancy, rapid growth in infants and decreased iron absorption because of stomach resection or intestinal malabsorption. Poor dietary iron intake may play a role, but is unusual as the sole cause of deficiency in adults.
Increased Ferritin Levels
Elevated ferritin levels may be seen in a variety of conditions, both with and without increased iron stores. Hemochromatosis is a genetic disorder resulting in excess uptake of iron from the digestive system and eventual tissue damage from iron overload. Genetic testing is available for diagnosis, but the laboratory finding of a markedly elevated ferritin level is quite characteristic. Levels greater than 1,000 mcg/L (ng/mL) are often present, as reported by Mayo Medical Laboratories. Other causes of increased ferritin due to iron overload include hemolytic anemia, multiple blood transfusions and some types of refractory anemia.
Ferritin is also one of the proteins in the body that may increase in concentration in response to chronic stimulation, known as acute phase reactants. Chronic inflammation, liver disease and some cancers can cause a non-specific increase in ferritin without increased iron stores.
Misleading Normal Ferritin Levels
Because ferritin is an acute phase reactant, expected decreases in blood ferritin with iron deficiency may not always develop in a person with two different conditions. A reactive increase from chronic inflammation can counteract the decrease due to low iron stores, resulting in a falsely normal ferritin level.
Interpretation
Additional blood tests including serum iron level, total iron binding capacity and complete blood count may also be ordered along with the ferritin level. These test results and the medical history considered together can help guide any further evaluation or treatment necessary.
References
- MedlinePlus: Ferritin
- "Clinical Diagnosis and Management by Laboratory Methods, 19th Edition"; John Bernard Henry M.D., Editor; 1996
- Mayo Clinic: Mayo Medical Laboratories: Ferritin, Serum
