Ferritin is the primary iron storage protein in the body, reflecting total body iron stores under normal conditions. It also functions as an acute-phase reactant, rising during inflammation, infection, and various disease states, which can complicate interpretation of iron status. Ferritin stores iron in a soluble, non-toxic form within cells, primarily in the liver, spleen, and bone marrow. Each ferritin molecule can store up to 4,500 iron atoms, releasing them when needed for hemoglobin synthesis, enzyme function, and other metabolic processes.
Ferritin is the primary intracellular iron storage protein and the most sensitive early indicator of iron depletion. Unlike serum iron, which fluctuates with meals and diurnal variation, ferritin provides a stable estimate of total body iron reserves. It is essential for evaluating unexplained fatigue, anemia, or suspected iron overload.
Low ferritin (typically <30 ng/mL) indicates depleted iron stores and may precede drops in hemoglobin. Elevated ferritin can reflect iron overload (hemochromatosis), but is also an acute-phase reactant — meaning it rises with inflammation, infection, and liver disease independent of iron status.
Iron losses in active individuals occur through sweat, gastrointestinal microbleeding (especially with NSAID use), foot-strike hemolysis in runners, and menstruation. Studies show that athletes — particularly female endurance athletes — have higher prevalence of iron depletion compared to sedentary controls. Because ferritin is an acute-phase reactant, it is most accurately interpreted when HS-CRP is concurrently normal.
Turnaround Time
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Fasting Required
No
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