Ferritin: what it is, what it tells you and why we test it

Ferritin is your body’s iron store. Its level in your blood shows how much iron you have put aside. It is usually the first number to drop when iron runs short, before haemoglobin does.

Why we test it

Iron carries oxygen to your muscles and brain. When you are short of it, your body uses the store and ferritin drops.

Your blood count can stay normal for a long time while the store empties. That is why ferritin finds a shortage before other tests do.

It matters when it is high too: it can signal a fatty liver or inflammation.

What it tells you, and what it does not

If it is low, iron is almost always running out.

If it is high, that does not have to mean too much iron. More often a fatty liver, inflammation or alcohol is behind it.

And during inflammation it can look normal even when the store is low.

That is why it is read together with other tests:

• Serum iron: The iron in your blood today
• Transferrin saturation: How much iron is ready to use
• CRP: Whether there is inflammation
• Blood count: Whether haemoglobin is already low

Normal ferritin levels

The lab decides what is normal. It is usually 13 to 150 ng/mL for women and 30 to 400 for men. Your own report may print different limits.

Watch out below 30: the iron store is already low, even though many lab reports for women call it normal.

In the Rosa report you also see your optimal range and what to do to reach it or stay in it.

What your result means

Find the row for your result, in ng/mL. Which values are dangerous? Below 15 and above 500 should always be seen by a doctor.

• Below 15: Iron deficiency. Your iron store is almost empty. Talk to a doctor to find the cause.
• 15 to under 30: Low store. Many lab reports for women call this normal, but the store is already low. Check your haemoglobin too, and look for the cause with your doctor.
• 30 up to your report’s limit, Usually 150 for women, 400 for men: Normal. Usually the store is enough, but inflammation can hide a low one. In the Rosa report you also see whether you are in your optimal range.
• Above your report’s limit, up to 500: High. Usually a fatty liver or inflammation is behind it, more rarely too much iron. Read it with CRP and the liver tests (GGT and ALT), and talk to your doctor.
• Above 500: Very high. It can come from serious inflammation, liver disease or too much iron. Talk to a doctor.

If your ferritin is high or low

• High ferritin: It is usually not too much iron. More often a fatty liver or inflammation is behind it.
• Low ferritin: Your iron store is running out, often before anaemia.

What can skew the result

A few things change the number for a while. It helps to know them before you read it.

• A recent infection: Even a flu can raise it for a few weeks. If so, repeat the test later.
• Alcohol: Drinking often can push it up.
• Iron supplements: They push it up. Tell your doctor.
• Biotin: It is in many hair and nail supplements and can make ferritin read lower than it is. If you take it, ask your doctor whether to pause it for at least two days before the test, and tell the lab.

When to worry

Talk to a doctor if:

• Your ferritin is below 15.
• Your ferritin is above 500.
• It is low and your haemoglobin is low too.
• It is low and you are a man, or a woman after menopause.
• It is low and you do not know why.

With Rosa, a ferritin below 15 or above 500 is always flagged to a doctor.

Frequently asked questions

What is the difference between iron and ferritin? The iron in your blood, serum iron, changes a lot from day to day. Ferritin is the store: it shows far better how much iron you really have.

Is ferritin part of a routine blood test? Not always. The full blood count, the most common test, does not include it: it has to be asked for. It is in the Rosa panel.

Do I need to fast for a ferritin test? Not for ferritin. It is usually done with other tests that do need fasting, though, so it is best to arrive fasted.

Do the numbers change with age? In adults they change more between women and men than with age. After menopause, women’s numbers move closer to men’s.

How often should it be checked? For people who feel well there is no fixed rule: Rosa measures it once a year. After iron treatment or an infection it is checked sooner, if your doctor says so.

Sources

• British Society of Gastroenterology, guidelines for iron deficiency anaemia in adults. Gut, 2021. PMID 34497146
• EASL clinical practice guidelines on haemochromatosis. Journal of Hepatology, 2022. PMID 35662478
• World Health Organization, guideline on the use of ferritin to assess iron status. Geneva, 2020. ISBN 978-92-4-000012-4