Is Ferritin useful for Sport?

Ferritin is a key biomarker reflecting body iron stores. For athletes, ferritin levels can be informative because iron deficiency (low ferritin) impairs oxygen transport and endurance performance. Observational studies show that endurance athletes (e.g., runners, cyclists) are at higher risk for subclinical iron deficiency due to increased losses (sweat, hemolysis, GI bleeding). A ferritin level below 30 ng/mL is often considered iron deficiency, while values below 100 ng/mL may be borderline for athletes. However, ferritin is also an acute-phase reactant: inflammation, infection, or intense training can artificially elevate ferritin, masking a true deficiency. Therefore, ferritin should be interpreted alongside CRP, transferrin saturation, and hemoglobin. Routine ferritin screening without clinical indication is not evidence-based; it may be useful when symptoms like fatigue, performance decline, or recurrent injuries appear. Caveat: iron overload (hemochromatosis) is also harmful. Conclusion: Ferritin is useful for sport, but only in context with other markers and individual training load. Do not self-supplement without medical guidance.