Ferritin

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Ferritin is the protein in which the body stores iron. The ferritin level in the blood reflects the size of these iron stores and is the most important laboratory value for detecting iron deficiency.

What does ferritin measure?

Most ferritin is found in the liver, spleen and bone marrow, and a small part circulates in the blood. This blood level is roughly proportional to the iron reserves. A low value therefore reliably indicates empty stores – often before haemoglobin falls and anaemia develops.

Low ferritin

According to the World Health Organization, a ferritin below 15 µg/l in adults indicates iron deficiency. If inflammation is present at the same time, a higher threshold applies (below 70 µg/l), because ferritin rises with inflammation. In practice many laboratories and clinicians use somewhat higher limits; the reference range depends on the laboratory. Typical causes are menstrual bleeding, pregnancy, blood loss from the gut and low iron intake.

High ferritin

Raised values do not automatically mean too much iron. Ferritin is an acute-phase protein and increases with infections, chronic inflammation, liver disease, alcohol use, obesity and some tumours. True iron overload occurs, for example, in hereditary haemochromatosis, where transferrin saturation is usually clearly raised as well.

Putting the value in context

Ferritin is often measured together with a full blood count, transferrin saturation and CRP so that iron deficiency and inflammation can be told apart. Iron supplements should only be taken after medical assessment, as too much iron can also be harmful.

Frequently asked questions

What does a low ferritin mean?

Low ferritin indicates depleted iron stores. It is important to find the cause, such as blood loss, low iron intake or increased need.

Why can ferritin be normal despite iron deficiency?

Ferritin rises during inflammation. In infections or inflammatory diseases it can therefore mask iron deficiency; other values such as transferrin saturation then help.

Should I take iron just in case?

Better not. Iron should be taken after a medical assessment, because too much iron can be harmful and the cause of a deficiency needs to be found.

Related terms

• Iron deficiency
• Iron metabolism
• Haemochromatosis
• Anaemia
• Haemoglobin
• Ferritin index
• Hepcidin

Sources

• WHO guideline on use of ferritin concentrations to assess iron status in individuals and populations (2020)
• Onkopedia guideline Iron deficiency and iron deficiency anaemia (DGHO, Germany)

This entry is for general information only and does not replace medical advice. Last updated: November 2026.