What can the Ferritin Eisenmangel tell you — and what not?

Ferritin is a key marker for iron deficiency, but it has important limitations. A low ferritin level (<30 ng/ml) reliably indicates depleted iron stores – that's its strength. What ferritin cannot tell you: functional iron deficiency (when ferritin is normal or elevated but iron is not properly utilized, e.g., due to inflammation). Ferritin is an acute-phase reactant; during infections, chronic diseases, or liver conditions it can be falsely elevated, masking a true deficiency. Therefore, ferritin should always be interpreted together with CRP, transferrin saturation, and possibly soluble transferrin receptor. A single ferritin value without clinical context is insufficient for diagnosing iron deficiency. The test is standardized, but reference ranges vary between labs. If iron deficiency is suspected, a doctor should order a complete iron status workup.