Ferritin blood test: what low, normal and high ferritin mean

Ferritin is a protein that stores iron. A ferritin blood test shows roughly how much iron your body has in reserve. A low ferritin almost always means your iron stores are running low. A high ferritin is less straightforward: it can mean too much iron, but more often it is a sign of inflammation, liver strain or alcohol.

A normal ferritin is reassuring, but it does not rule everything out. Because ferritin rises when the body is inflamed, it can look normal even when iron stores are low. That is why doctors usually read ferritin alongside other iron tests and a full blood count.

What is a normal ferritin level?

Ferritin is measured in micrograms per litre (µg/L). The normal range differs between laboratories, and between men and women, so always check the range printed next to your result. Women who have periods often have lower ferritin than men.

Being "in range" is not the whole story. NHS guidance treats a ferritin below 30 µg/L as confirming iron deficiency in most adults, even though some laboratory ranges start lower than that. So a result at the bottom of the range can still be worth acting on, especially if you have symptoms.

What does low ferritin mean?

Low ferritin means your iron stores are depleted. If it carries on, your body cannot make enough haemoglobin, and you develop iron deficiency anaemia. Ferritin often falls before anaemia shows up, so it can pick up the problem early.

Symptoms of low iron

• tiredness and lack of energy
• shortness of breath on exertion
• headaches
• pale skin
• hair shedding and brittle nails
• restless legs
• heart palpitations

Some people with low ferritin feel completely well.

Common causes of low ferritin

• Heavy periods, the most common cause in women of reproductive age.
• Pregnancy and recent childbirth.
• Diet with little iron, including some vegetarian and vegan diets.
• Poor absorption, for example coeliac disease or after some stomach operations.
• Blood loss from the gut, which may be hidden. This matters most in men and in women who no longer have periods.
• Regular blood donation or endurance training.

Low iron is a finding, not a diagnosis. The important step is working out why it is low. For men of any age, and women after the menopause, unexplained iron deficiency needs to be looked into by a GP, because the gut can be a source of slow blood loss.

What does high ferritin mean?

A raised ferritin is common and is often found by chance. The usual causes are:

• Inflammation or infection. Ferritin rises with a recent virus, inflammatory conditions or after surgery.
• Alcohol. Regular drinking is a frequent cause.
• Fatty liver and being overweight, often alongside high blood sugar or cholesterol.
• Other liver conditions.
• Iron overload, including haemochromatosis, an inherited condition where the body absorbs too much iron. It is more common in people of northern European, particularly Irish, Scottish and Welsh, descent.
• Iron supplements or iron treatment taken recently.

To tell these apart, a doctor looks at your transferrin saturation. A high ferritin with a normal transferrin saturation usually points to inflammation, liver or lifestyle causes. A high ferritin with a high transferrin saturation raises the possibility of iron overload, and your GP may arrange further tests, including genetic testing for haemochromatosis.

What do the other iron tests mean?

A ferritin result is more useful with these alongside it:

• Serum iron: the iron in your blood at that moment. It goes up and down through the day and after meals, so it is not reliable on its own.
• TIBC (total iron binding capacity): tends to rise when iron is low.
• Transferrin saturation: how much of your iron transport protein is carrying iron. Low in iron deficiency, high in iron overload.
• Full blood count: shows whether you have anaemia, and whether your red cells are small, which is typical of iron deficiency.

Low B12 or folate can cause similar tiredness and a different type of anaemia, so they are often checked at the same time.

Do I need to prepare for a ferritin test?

You do not need to fast for ferritin. A morning appointment is preferred when serum iron is measured too, as iron levels vary through the day. Tell us if you take iron tablets or have had iron treatment recently, as this changes how your results are read. If you have had a cold or infection in the last couple of weeks, your ferritin may be higher than usual.

Which test should I book?

Our Iron & B12 Check (£89) includes ferritin, iron, TIBC, transferrin saturation, active B12 and red cell folate. Our Iron & B12 + FBC (£109) adds a full blood count, so you can see whether low iron has led to anaemia. Ferritin is also part of our Full Body Health Check.

If tiredness is the main reason you are testing, our article on blood tests for feeling tired all the time explains what else is worth checking.

What happens with your results

A GMC-registered doctor reviews every result before you see it and adds a comment explaining what it means for you. If your ferritin is very low or high, or the pattern suggests something that needs looking into, a doctor contacts you directly and can advise on next steps with your NHS GP.

See our fatigue and energy tests, or search for ferritin in the A to Z of blood tests.

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