Ferritin is a protein that stores iron. The body increases serum ferritin production when excess iron is absorbed, so serum ferritin levels are a good indication of the body's iron stores. Note that serum ferritin values may be artificially increased by underlying cancer or inflammatory/infectious conditions.
Patients with elevated transferrin saturation test values should proceed with serum ferritin testing and additional workup as warranted.
Consistently excessive blood loss will result in a negative iron balance which will result in lowered serum ferritin levels. Iron deficiency is a cause as well as consequence of menorrhagia. Body stores of iron are best reflected by serum ferritin. Ferritin levels will drop before changes in the blood count begin. Anemia may not yet be present when serum ferritin levels are getting low.