Ferritin
Serum ferritin
Ferritin is the protein that stores iron in your body. It is the single best indicator of whether your iron reserves are full or running out.
Reference range
µg/L- Women
- 15–150 µg/L
- Men
- 30–400 µg/L
Reference ranges differ between laboratories and assays. Always read your result against the range printed on your own report.
What Ferritin measures
Iron is dangerous when it floats around freely, so your body packs it into ferritin — a hollow protein shell that holds up to about 4,500 iron atoms. Most ferritin sits inside cells, mainly in the liver, spleen and bone marrow. A small amount leaks into the bloodstream, and that is what a blood test measures.
That small leaked fraction turns out to track total body iron reserves closely. This is why ferritin is measured instead of iron itself: serum iron swings by the hour depending on what you ate, while ferritin reflects the stock in the warehouse rather than what happens to be on the loading dock.
Reference ranges differ substantially between women and men, because menstruation removes iron every month. A value that is unremarkable for a man can sit at the very bottom of the range for a woman.
Why it gets tested
Usually to investigate fatigue, hair loss, shortness of breath on exertion, or a low haemoglobin result. It is also the standard check before and during iron supplementation, and in monitoring conditions that cause iron overload.
Commonly associated with low values
- Depleted iron stores — the most common nutritional deficiency worldwide
- Blood loss, most often menstrual or gastrointestinal
- Reduced absorption, for example in coeliac disease or after gastric surgery
- Intake that does not keep up with demand, as in pregnancy or endurance training
Commonly associated with high values
- Inflammation or infection — ferritin is an acute phase protein and rises with them
- Liver disease, since damaged liver cells release stored ferritin
- Iron overload, including hereditary haemochromatosis
- Regular alcohol consumption
What can shift the result
- Any infection or inflammatory flare can push ferritin up for weeks, which can mask a genuine deficiency underneath
- Recent intense exercise raises it temporarily
- Values rise gradually with age in men
Questions
Can ferritin be normal and iron still be low?
Yes, and this is the classic trap. Ferritin rises with inflammation, so an infection, an autoimmune flare or a recent injury can lift it into the normal range while iron stores are genuinely empty. This is why ferritin is often interpreted alongside CRP — if CRP is raised, a normal ferritin cannot be taken at face value.
What ferritin level counts as low?
Laboratories usually flag values below 15 µg/L for women and below 30 µg/L for men. Many clinicians consider symptoms of iron deficiency plausible well above that threshold, particularly under 30 µg/L, but there is no universal agreement and the decision belongs with your doctor.
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This page is general information about a laboratory value. It is not a diagnosis and does not replace medical advice. Discuss your own results with a doctor, who can read them in the context of your history and symptoms.