Ferritin and iron: what does a low ferritin mean?

Ferritin is a protein that stores iron and is one of the most useful laboratory markers of the body’s iron reserves. A low ferritin strongly supports iron deficiency, but interpretation is not always as simple as comparing one result with a reference interval.

Why is ferritin useful?

Ferritin generally falls as iron stores become depleted, often before anaemia becomes pronounced. For this reason it is commonly assessed together with the full blood count and, when appropriate, serum iron, transferrin or transferrin saturation.

Can ferritin be “normal” despite iron deficiency?

Yes. Ferritin is also an acute-phase reactant and may rise in inflammation, infection and some chronic diseases. In these settings, a result within the laboratory reference interval does not always exclude iron deficiency, and additional markers or clinical context may be needed.

Should someone simply start iron supplements?

Not automatically. Iron deficiency has a cause, such as inadequate intake, increased requirements or blood loss. Treating the number without investigating the reason may delay identification of an important underlying problem. Supplementation should therefore be discussed with the treating physician.

Scientific sources

1. World Health Organization — Use of ferritin concentrations to assess iron status.
2. NIH Office of Dietary Supplements — Iron: Fact Sheet for Health Professionals.
3. Johns Hopkins Medicine — Iron-Deficiency Anemia.

Last scientific review: 25 August 2026.