Ferritin

The body's iron storage protein — and a key inflammation signal.

What it is

Ferritin is the protein that stores iron in cells. Blood ferritin levels reflect total body iron stores. It is also an acute-phase reactant, meaning it rises with inflammation independent of iron status.

Why it matters

Iron deficiency is one of the most common nutritional deficiencies and a major driver of fatigue in cancer patients. But ferritin can be falsely elevated by inflammation, masking true deficiency. Interpreting ferritin alongside CRP and serum iron gives the full picture.

How to test

Standard blood test. Best interpreted alongside CRP and serum iron.

This information is for educational purposes only. Always discuss testing and interpretation of results with your care team.

Optimal range

Below 20–30 µg/L

iron deficiency — often symptomatic fatigue

30–200 µg/L

normal range

Above 300 µg/L

may reflect inflammation or iron overload

How often

Every 3–6 months.