Ferritin

What is Ferritin?

Ferritin is your iron store: the reserve your body keeps for later. It says more about your store than a single iron measurement. Enough iron feeds your energy, concentration and the production of red blood cells. Too little can cause fatigue; a great deal can point to inflammation.

Clinical frame

Ferritin is the measure of iron stores: a small, proportional fraction of the storage protein leaks into the plasma. A low ferritin is almost always specific for depleted stores. Without inflammation, a value below 30 μg/L reliably indicates iron deficiency, a threshold that replaces the historical laboratory limits, which were too low ^{[1] [2]}.

Ferritin is, however, also an acute-phase protein: inflammation, liver disease, kidney failure and cancer raise it and can mask a true deficiency. With inflammation the threshold shifts to 100 μg/L and transferrin saturation (below 20 %) is more reliable for demonstrating iron restriction ^[1].

A raised ferritin is common and usually not iron overload: the most frequent cause is metabolic hyperferritinaemia in metabolic syndrome, fatty liver, obesity and daily alcohol use, alongside inflammation and liver disease. Consider haemochromatosis when transferrin saturation is persistently raised, to be confirmed by HFE genotyping ^[3].

What moves this value?

Blood loss (for example menstruation), little iron in the diet or a period of inflammation can make the value fall or rise.

Iron-rich food (meat, legumes, green vegetables) with a little vitamin C alongside steadily replenishes the store. Easy to measure again after a few months.

What this connects

• Hemoglobin
• hsCRP
• Iron

References

1. Fletcher, A., Forbes, A., Svenson, N. & Wayne Thomas, D. Guideline for the laboratory diagnosis of iron deficiency in adults (excluding pregnancy) and children. Br J Haematol 196, 523–529 (2022). doi.org/10.1111/bjh.17900
2. Truong, J. et al. The origin of ferritin reference intervals: a systematic review. Lancet Haematol 11, e530–e539 (2024). doi.org/10.1016/S2352-3026(24)00103-0
3. Valenti, L. et al. Consensus Statement on the definition and classification of metabolic hyperferritinaemia. Nat Rev Endocrinol 19, 299–310 (2023). doi.org/10.1038/s41574-023-00807-6