A Low or High Iron and Ferritin: What Does It Mean?

Serum iron and ferritin are tests used to assess the body’s iron status. But they do not show the same thing.

• Serum iron — gives information about how much iron is circulating in the blood at that moment.
• Ferritin — is one of the most important indicators used to assess the body’s iron stores.

So a diagnosis is not made from a serum iron being low or high on its own.

What is ferritin?

Ferritin is a protein that allows iron to be stored in cells. In most situations the ferritin level in the blood gives information about the body’s iron stores.

A low ferritin is a strong finding for iron deficiency.

But ferritin is not only a protein that reflects iron stores. It is also an acute phase reactant, which can rise during inflammation. So a high ferritin does not always mean there is too much iron in the body.

Why does ferritin fall?

The most important cause of a low ferritin is a fall in iron stores. The main reasons for this are:

Blood loss

• Heavy or prolonged menstrual bleeding
• Hidden bleeding from the stomach or bowel
• Other recurring blood loss

Not taking in enough iron

Not getting enough iron from the diet.

An increased need for iron

The need for iron can rise particularly during periods of growth and in pregnancy.

Malabsorption

Iron not being absorbed properly from the bowel. For example:

• Coeliac disease
• Some conditions of the stomach and small bowel
• Operations on the stomach or bowel

can affect iron absorption.

Can ferritin be low while haemoglobin is normal?

Yes. This is quite an important point.

As iron deficiency develops, iron stores start to empty first. At this stage ferritin may already have fallen while haemoglobin is still normal. If the deficiency then progresses, haemoglobin can fall too and iron deficiency anaemia can develop.

So:

• Low ferritin + normal haemoglobin — iron stores may have fallen.
• Low ferritin + low haemoglobin — iron deficiency anaemia becomes more likely.

What is iron deficiency anaemia?

When iron deficiency has progressed far enough, haemoglobin production is affected and anaemia can develop. The patient may have:

• Weakness
• Tiring easily
• Breathlessness
• Palpitations
• Dizziness
• Pallor
• Difficulty concentrating

But some people have no obvious symptoms.

What is the real question in iron deficiency?

Iron deficiency is a diagnosis in itself, but the real question is usually: “Why has the iron fallen?”

Simply giving iron tablets to raise the value is not always enough. In adults in particular, the source of blood loss may need looking into.

Can bleeding in the digestive tract cause iron deficiency?

Yes.

Small amounts of blood can be lost from the stomach or bowel over a long period. This bleeding is not always visible; a person’s stool can look completely normal.

Causes of gastrointestinal blood loss can include:

• Ulcers of the stomach or duodenum
• Gastritis
• Colon polyps
• Colorectal cancer
• Inflammatory bowel disease
• Bleeding from blood vessels
• Other gastrointestinal conditions

Unexplained iron deficiency matters particularly in men and in women after the menopause, from the point of view of gastrointestinal blood loss. This does not automatically mean cancer; but the cause does need looking into.

Is a gastroscopy or colonoscopy needed in iron deficiency?

Not every low iron or ferritin leads automatically to endoscopy and colonoscopy. The decision is made by weighing:

• Age
• Sex
• Menopausal status
• Haemoglobin level
• How severe the deficiency is
• Gastrointestinal symptoms
• Family history
• Findings of visible or hidden bleeding
• Previous investigations

Some people will need a gastroscopy, a colonoscopy, or both.

Why is serum iron not enough on its own?

Serum iron can change during the day and can be affected by:

• Diet
• Taking iron tablets
• Inflammation
• Various illnesses

So iron status is not assessed from serum iron alone. Where needed, your doctor will weigh ferritin, transferrin, total iron binding capacity (TIBC), transferrin saturation, haemoglobin, MCV and CRP together.

What does a high ferritin mean?

There is a very common mistake here: “High ferritin = there must be too much iron in the body” is not correct.

Ferritin is an acute phase reactant, so it can rise during inflammation in the body. Causes of a high ferritin can include:

• Infections
• Inflammatory conditions
• Liver disease
• Conditions associated with metabolic disorders
• Alcohol use
• Iron overload
• Some haematological and other conditions

So when the cause of a high ferritin is being looked into, other tests are considered as well.

How is iron overload recognised?

To assess the likelihood of iron overload where ferritin is high, transferrin saturation matters particularly.

Your doctor will weigh the ferritin, serum iron, transferrin/TIBC and transferrin saturation results together. Where needed, further investigation for inherited iron overload conditions — haemochromatosis in particular — may be carried out.

A high ferritin on its own does not make a diagnosis of haemochromatosis.

Does ferritin rise in liver disease?

Yes. Ferritin can be found raised in liver disease. For example it can rise in some fatty liver conditions, in hepatitis, in alcohol-related liver damage and in other liver conditions.

For this reason it can be useful to assess ALT, AST, GGT and the other liver tests where ferritin is high.

Does ferritin rise during an infection?

Yes. Because ferritin can rise during inflammation, it can be found above normal during an acute infection. A high ferritin result should therefore be weighed together with CRP and the other clinical findings.

Can there be iron deficiency even when ferritin is normal?

In some situations, yes.

Particularly in people with inflammation, ferritin may have risen or stayed within the normal range because of that inflammation. This can mask a real iron deficiency.

So where there is clinical suspicion, rather than looking at ferritin alone, results such as transferrin saturation, serum iron, TIBC/transferrin, CRP and the blood count are weighed together.

Can I start iron tablets myself?

This is not advised.

When iron deficiency is found, determining both how severe it is and what is causing it matters. Taking iron unnecessarily can cause side effects such as:

• Nausea
• Abdominal pain
• Constipation
• Darkening of the stool

And in someone who genuinely has iron overload, taking iron unnecessarily is not appropriate.

Do iron tablets make stools black?

Yes. Iron preparations taken by mouth can make the stool look dark, even close to black.

But tarry, sticky, foul-smelling black stools — particularly together with weakness, dizziness or abdominal symptoms — can suggest gastrointestinal bleeding.

So it is not right to put every black stool down to iron tablets automatically.

When is quicker assessment needed?

What is done if your result is abnormal?

1. Do not look at a single value. Serum iron, ferritin and haemoglobin do not show the same thing.
2. Look at your blood count. Haemoglobin and MCV give important information.
3. If ferritin is low, look into why. Unexplained blood loss in particular should not be overlooked.
4. If ferritin is high, do not assume “I have too much iron”. There can be many causes, including inflammation and liver disease.
5. Transferrin saturation may matter. It is assessed particularly where iron overload is suspected.
6. Do not start or stop iron on your own. Treatment should be planned according to the cause.

Remember

• A low ferritin Strongly suggests that iron stores have fallen.
• Low ferritin + normal haemoglobin May be iron deficiency before anaemia has developed.
• Low ferritin + low haemoglobin Suggests iron deficiency anaemia.
• A high ferritin Does not always mean an excess of iron.
• High ferritin + high transferrin saturation May call for assessment for iron overload.
• Normal ferritin + inflammation May not entirely rule out iron deficiency in some patients.