Ferritin is a large spherical protein containing 24 non-***valent bonded subunits, which form a shell surrounding the center, which contains varying amounts of ferric hydroxyphosphate. One molecule of ferritin binds between 4,000 and 5,000 atoms of iron, making it the most important form of iron storage in the body, and its concentration is directly proportional to the amount of iron accumulated in the body.

Serum ferritin levels in healthy adults range from 20 (±10) to 300 (±100) ng/mL in men and 10 (±5) to 150 (±50) ng/mL in women.

Concentrations of less than 10 ng/mL or 15 ng/mL are characteristic of mild iron deficiency anemia.

Serum ferritin values are generally higher than 300 ng/mL or 400 ng/mL in iron overload.

Measurement of serum ferritin is important for diagnosing and monitoring iron deficiency. A decrease in ferritin levels is indicative of iron deficiency. Iron overload or spontaneous hemochromatosis is associated with elevated ferritin levels.