Iron deficiency anaemia

What causes iron deficiency anaemia?

There are many reasons a person can end up short of iron. In men and in women who have already been through menopause, the most common reason is bleeding somewhere in the stomach or intestines.

This bleeding can come from a stomach ulcer, stomach cancer, bowel cancer, or from taking non steroidal anti inflammatory drugs (NSAIDs) regularly.

In women who are still menstruating, heavy periods and pregnancy are the most common causes, since your body needs extra iron to support your baby during pregnancy.

Unless you are pregnant, it is unusual for iron deficiency anaemia to be caused by diet alone. Still, if your diet is low in iron, you may be more likely to develop anaemia if you also have one of the problems mentioned above.

Read more about the causes of iron deficiency anaemia below.

Causes of iron deficiency anaemia

Iron deficiency anaemia happens when the body does not have enough iron to make sufficient red blood cells. Red blood cells are what carry oxygen around your body.

A shortage of iron can come from several different causes. Some of the most common ones are explained below.

Monthly periods

For women who are still menstruating, periods are the most common cause of iron deficiency anaemia. Usually it is only women with heavy periods who go on to develop this condition. When heavy bleeding continues over several menstrual cycles in a row, doctors call it menorrhagia.

Pregnancy

It is also quite common for women to develop iron deficiency during pregnancy. This happens because your body needs extra iron to make sure your baby gets enough blood, oxygen, and nutrients. Some pregnant women need to take an iron supplement, while others just need to eat more iron rich foods.

Read more about vitamins and minerals during pregnancy.

Gastrointestinal blood loss

The gastrointestinal tract is the part of your body that digests food, including the stomach and intestines. Bleeding here is the most common cause of iron deficiency anaemia in men, and in women who have already gone through menopause (when periods stop for good).

Most people with this kind of bleeding do not notice any obvious blood in their stools and do not notice any change in their bowel habits. Some of the specific causes are described below.

Non steroidal anti inflammatory drugs

NSAIDs can cause bleeding in the stomach. Ibuprofen and aspirin are two commonly used NSAIDs. If your doctor thinks your medicine is causing gastrointestinal bleeding, they may be able to prescribe something gentler. However, do not stop taking a prescribed medicine unless your doctor tells you to.

Stomach ulcers

The acid in your stomach helps digest food, but sometimes it wears into the stomach lining itself. When that happens, it forms an open sore, known as a stomach ulcer or peptic ulcer. These ulcers can cause the stomach lining to bleed, which can lead to anaemia. In some cases the bleeding is severe enough that you vomit blood or pass blood in your stools, but if the ulcer bleeds slowly you may not notice any symptoms at all.

Gastrointestinal cancer

In a small number of cases, bleeding in the gastrointestinal tract is caused by cancer, usually stomach cancer or bowel cancer. When trying to find the cause of your anaemia, your doctor will check for possible signs of cancer. If cancer is suspected, you will be referred to a gastroenterologist (a specialist in digestive conditions) for a closer look, so that if cancer is found, treatment can start as early as possible.

If you are 60 years old or older and have iron deficiency anaemia, your doctor should refer you to a specialist to rule out bowel cancer, and your appointment with the specialist should happen within two weeks of the referral.

Angiodysplasia

Gastrointestinal bleeding can also come from a condition called angiodysplasia, where abnormal, fragile blood vessels near the surface of the gut cause bleeding.

Chronic kidney disease

People with chronic kidney disease (CKD) often go on to develop iron deficiency anaemia. Most people who have both CKD and iron deficiency anaemia are given iron through injections, though daily tablets may be tried first. You can read more about treating anaemia in people with CKD on the website of the National Institute for Health and Care Excellence (NICE).

Other causes

Other conditions or events that cause blood loss and may lead to iron deficiency anaemia include:

inflammatory bowel disease, a condition causing redness and swelling in the digestive system, such as Crohn's disease and ulcerative colitis

oesophagitis, inflammation of the food pipe (oesophagus) caused by stomach acid leaking into it

schistosomiasis, an infection caused by parasites, found mainly in sub Saharan Africa

blood donation, since giving a large amount of blood can sometimes lead to anaemia

trauma, such as a serious accident like a car crash, which can cause major blood loss

nosebleeds, since frequent nosebleeds can lead to anaemia, though this is rare

haematuria (blood in the urine), which rarely causes anaemia on its own but may point to another condition

Malabsorption

Malabsorption means your body is unable to absorb iron properly from food, and it is another possible cause of iron deficiency anaemia. This can happen if you have coeliac disease, a common digestive condition involving an adverse reaction to gluten, or if you have had surgery to remove all or part of your stomach (gastrectomy).

Lack of iron in your diet

Unless you are pregnant, it is unusual for iron deficiency anaemia to be caused by a low iron diet alone. However, a diet low in iron can raise your risk of anaemia if you also have any of the conditions mentioned above.

Some studies suggest that vegetarians and vegans face a somewhat higher risk of iron deficiency anaemia because their diet does not include meat. If you follow a vegetarian or vegan diet, you can still get enough iron from other foods, such as:

beans

nuts

dried fruit, such as dried apricots

wholegrains, such as brown rice

fortified breakfast cereals

soybean flour

most dark green leafy vegetables, such as watercress and kale

If you are pregnant, you may need to eat more iron rich foods during pregnancy to help prevent iron deficiency anaemia.

Read more about vegetarian and vegan diets.

Finding the cause

To work out what is behind your anaemia, your doctor may ask about your lifestyle and medical history, including:

your diet, to understand what you typically eat and whether it includes iron rich foods

any medicines you take, to see whether you have been regularly taking something that can cause bleeding in the stomach or intestines, such as ibuprofen or aspirin

your menstrual pattern, if you are a woman, since your doctor may ask whether your periods have been particularly heavy

your family history, since you will be asked whether close family members have had anaemia or a history of gastrointestinal bleeding or blood disorders

Iron deficiency anaemia is common during pregnancy. If you are pregnant, your doctor will usually only look for another cause if a blood test shows an especially low haemoglobin level, or if your symptoms or medical history suggest something else may be responsible.

Physical examination

A physical examination is usually only needed if the cause of your anaemia has not become clear from your history and symptoms alone. In that case, your doctor may:

examine your abdomen to check for physical signs of gastrointestinal bleeding

look for signs of heart failure, such as swollen ankles, since heart failure can share some symptoms with iron deficiency anaemia

Two other possible examinations are described below.

Rectal examination

A rectal examination is usually only needed if you are bleeding from your bottom. It is a routine procedure that helps your doctor check for anything in the gastrointestinal tract that could be causing bleeding. Your doctor will gently insert a lubricated, gloved finger into your bottom to feel for anything unusual. There is no need to feel embarrassed, since this is a procedure doctors carry out regularly. It should not be painful, though you may feel some slight discomfort for about a minute.

Pelvic examination

Women may have a pelvic examination if their doctor suspects heavy menstrual bleeding (menorrhagia) could be the cause of their anaemia. During this examination, your doctor will check your vulva and labia (external sex organs) for signs of bleeding or infection. They may also examine you internally, gently inserting lubricated, gloved fingers into your vagina to check whether your womb (uterus) feels tender or enlarged. A pelvic examination will never be carried out without your consent, and you are welcome to have someone with you during it.

Referral to a specialist

In some cases, your doctor may refer you to a gastroenterologist, a specialist in digestive conditions, for a more detailed examination. For example, you might be referred if your doctor cannot identify a cause and your haemoglobin level is particularly low, or if there is a chance, even a small one, that your symptoms could be linked to stomach or bowel cancer. If you are a woman with heavy periods who does not respond to iron supplements, you may be referred to a gynaecologist instead.

If you notice symptoms of iron deficiency anaemia, such as tiredness, shortness of breath and heart palpitations, it is best to see your doctor. A simple blood test can usually confirm the diagnosis.

Your doctor may also examine you and ask several questions to help find out what is causing your anaemia.

Blood test

To diagnose iron deficiency anaemia, a blood sample is taken from a vein in your arm and a full blood count is done. This means all the different types of blood cells in the sample are measured.

If you have anaemia:

• your haemoglobin level, the substance that carries oxygen in your blood, will be lower than normal
• you will have fewer red blood cells, which contain haemoglobin, than normal
• your red blood cells may be smaller and paler than usual

Your doctor may also check a substance called ferritin, a protein that stores iron in your body. If your ferritin level is low, it means your body does not have much iron stored, and you may have iron deficiency anaemia.

Vitamin B12 and folate deficiency

If your doctor suspects that your anaemia may be caused by a lack of vitamin B12 or folate, these levels may also be tested. Folate works together with vitamin B12 to help your body make red blood cells.

Vitamin B12 and folate deficiency anaemia is more common in people over the age of 75.

Treatment for iron deficiency anaemia means taking iron supplements to bring your low iron levels back up. This works well for most people, and the condition rarely leads to long-term problems.

You will need to be checked every few months to make sure the treatment is working and that your iron levels have returned to normal.

The underlying cause will also need to be treated so the anaemia does not come back. Your doctor may also recommend increasing the amount of iron in your diet.

Good sources of iron include:

• dark green leafy vegetables, such as watercress and curly kale
• iron fortified cereals or bread
• brown rice
• pulses and beans
• nuts and seeds
• meat, fish and tofu
• eggs
• dried fruit, such as dried apricots, prunes and raisins

Read more about treating iron deficiency anaemia.

Further problems

If iron deficiency anaemia is left untreated, it can make you more prone to illness and infection, since low iron affects the body's natural defence system, the immune system.

Severe iron deficiency anaemia may raise your risk of complications affecting the heart or lungs, such as an abnormally fast heartbeat (tachycardia) or heart failure, where the heart cannot pump enough blood around the body at the right pressure.

Pregnant women with severe or untreated anaemia also face a higher risk of complications before and after birth.

Read more about the complications of iron deficiency anaemia.

Treating iron deficiency anaemia

Treatment usually involves taking iron supplements, changing your diet to increase your iron intake, and treating whatever is causing the anaemia in the first place.

Iron supplements

Your doctor will prescribe an iron supplement to restore the iron your body is missing. The one most commonly prescribed is ferrous sulphate, taken as a tablet, usually twice a day.

Some people notice side effects when taking iron supplements, including:

• abdominal (tummy) pain
• constipation or diarrhoea
• heartburn
• feeling sick
• black stools (faeces)

These side effects usually settle down over time. However, if they are troublesome, your doctor may suggest taking the tablets with food or shortly after eating.

Your doctor may also advise taking just one or two tablets a day instead of three if the side effects are hard to manage.

If you cannot tolerate ferrous sulphate because of severe side effects, you may be prescribed a different supplement called ferrous gluconate. This tends to cause fewer side effects, since it contains a less concentrated dose of iron, though it may take longer for your iron levels to be restored.

In some cases, for example if you have chronic kidney disease (CKD), iron injections may be recommended instead of tablets.

As with all medicines, keep iron supplements out of the reach of children. An overdose of iron supplements can be fatal in a young child.

Dietary advice

If a lack of dietary iron is thought to be contributing to your anaemia, your doctor will advise you on how to increase your intake.

Iron rich foods include:

• dark green leafy vegetables, such as watercress and curly kale
• iron fortified cereals or bread
• brown rice
• pulses and beans
• nuts and seeds
• white and red meat
• fish
• tofu
• eggs
• dried fruit, such as dried apricots, prunes and raisins

Your diet should include foods from all the major food groups to keep it healthy and balanced. Foods and drinks containing vitamin C are especially helpful, since vitamin C helps your body absorb iron.

On the other hand, consuming large amounts of certain foods, drinks and medicines can make it harder for your body to absorb iron. These include:

• tea and coffee
• calcium, found in dairy products such as milk
• antacids and proton pump inhibitors (PPIs), medicines used to relieve indigestion
• wholegrain cereals, which are a good source of iron themselves but contain phytic acid, which can stop your body absorbing iron from other foods and pills

If you are finding it difficult to include enough iron in your diet, you may be referred to a dietitian, a specialist in nutrition, who can give you detailed, personalised advice.

Treating the underlying cause

Your doctor will also need to make sure the underlying cause of your anaemia is treated so it does not happen again.

For example, if NSAIDs (non-steroidal anti-inflammatory drugs) are causing bleeding in your stomach, your doctor may switch you to a different medicine to help reduce the risk of further stomach bleeding.

Heavy periods can be treated with medication or, in particularly severe cases, surgery.

Monitoring

Your doctor will usually ask you to come back two to four weeks after starting iron supplements to check how well you have responded to treatment. You will have a blood test to check your haemoglobin levels.

If the results show improvement, you will be asked to keep taking the iron supplements and return in two to four months for another blood test.

Once your haemoglobin and red blood cell levels are normal, your doctor will usually recommend continuing the iron supplements for another three months to help build up your body's iron stores.

After this, you should be able to stop taking the supplements, depending on what caused your iron deficiency anaemia. Your condition will then be checked every three months over the course of a year, and again a year after that.

Continuing treatment

Sometimes, after a person's iron levels have been restored, they begin to fall again. This can happen if you are not getting enough iron in your diet, if you are pregnant, or if you have consistently heavy periods.

In such cases, you may be prescribed an ongoing iron supplement to help prevent the anaemia from returning. This is usually a tablet taken once a day.

If treatment is not working

If your iron levels are not improving, your doctor will first ask how regularly you have been taking your iron supplements. Some people are put off by the side effects, but it is important to know that your condition will not improve unless you keep taking the supplements as prescribed.

If you have been taking them correctly and your iron levels still have not improved, your doctor may refer you to a specialist for further assessment.

Iron deficiency anaemia rarely leads to serious or long-term complications, though some people do find that it affects their day-to-day life. Some of the more common complications are described below.

Tiredness

Iron deficiency anaemia can leave you feeling tired, worn out, and low on energy. Because of this, you may find you get less done at work, struggle to stay awake, or feel unable to keep up with regular exercise.

Increased risk of infections

Research shows that iron deficiency anaemia can affect the immune system, the body's natural line of defence. This makes you more vulnerable to infections.

Heart and lung problems

Adults with severe anaemia may be at risk of complications affecting the heart or lungs. For example, you might develop tachycardia, an abnormally fast heartbeat, or heart failure, a condition in which the heart cannot pump enough blood around the body at the right pressure.

Pregnancy complications

Pregnant women with severe anaemia face a higher risk of complications, particularly around the time of birth and afterwards. They may also be more prone to postnatal depression, which some women experience after childbirth.

Research suggests that babies born to mothers with untreated anaemia are more likely to:

• be born prematurely, before the 37th week of pregnancy
• have a low birth weight
• have iron level problems of their own
• perform less well on tests of mental ability

Restless legs syndrome

Some cases of restless legs syndrome are thought to result from iron deficiency anaemia, something doctors often call secondary restless legs syndrome. Restless legs syndrome is a common condition affecting the nervous system, causing an overwhelming, irresistible urge to move the legs, along with an unpleasant sensation in the feet, calves, and thighs. When it is caused by iron deficiency anaemia, restless legs syndrome can usually be treated with iron supplements.