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Iron-deficiency Anaemia

Iron-deficiency Anaemia

Anaemia is commonly caused by a lack of iron. The most common cause of lack of iron in the UK is heavy menstrual periods. There are many other causes. Bleeding into the gut (intestine) is a common cause in older people. Tests may be advised to find the cause of the anaemia. Treatment with iron tablets can correct the anaemia. Other treatments may be advised, depending on the cause.

Blood is made up of a fluid called plasma which contains:

  • Red blood cells - which take oxygen around the body.
  • White blood cells - which are part of the immune system and defend the body from infection.
  • Platelets - which help the blood to clot if we cut ourselves.
  • Proteins - and other chemicals that have various functions.

Red blood cells are made in the bone marrow. Millions of them are released into the bloodstream each day. A constant supply of new red blood cells is needed to replace old ones that break down. Red blood cells contain a chemical called haemoglobin. Haemoglobin transports oxygen from the lungs to all parts of the body. To keep making red blood cells and haemoglobin, you need a healthy bone marrow. Your diet is also important as a source of iron and certain vitamins that you need.

Anaemia means:

  • You have fewer red blood cells than normal; OR
  • You have less haemoglobin than normal in each red blood cell.

In either case, a reduced amount of oxygen is carried around in the bloodstream. The most common cause of anaemia in the UK is a lack of iron. Iron is needed to make haemoglobin. Anaemia caused by a lack of iron is called iron-deficiency anaemia (IDA).

Iron deficiency is a common cause of anaemia, often seen in pregnancy. Low iron levels may be caused by bleeding eg heavy periods or from the bowel (stomach ulcer, bowel cancer or piles) Sometimes the bowel can’t absorb enough iron, e.g. in coeliac disease.

A normal balanced diet will usually contain enough iron for your body's needs. A low level of iron, leading to anaemia, can result from various causes. Some are more serious than others, and include the following:

Heavy menstrual periods

Anaemia is common in women (of all ages) who have heavy periods. About 1 in 10 women will become anaemic at some point because of this. The amount of iron that you eat may not be enough to replace the iron that you lose during each period. Having heavy periods does not always lead to anaemia. Anaemia is more likely to develop if you have heavy periods and eat a diet that contains little iron.


A growing baby needs iron and will take it from the mother. Anaemia is common in pregnant women. It is more likely to develop during pregnancy if you eat a diet that has little iron.

Poor absorption of iron

Some conditions of the gut (intestine) lead to poor absorption of various foods, including iron. Coeliac disease is an example.

Bleeding from the gut

Several conditions of the gut can lead to bleeding. Sometimes this is sudden - for example, after a burst duodenal ulcer. Being sick (vomiting) or passing blood is obvious then.

Sometimes the bleeding is not obvious. A constant trickle of blood into the gut can be passed unnoticed in the stools (faeces). The iron that you may lose with the bleeding may be more than you eat. Conditions causing this include:

  • Stomach or duodenal ulcers.
  • Inflammation of the large intestine (colitis).
  • Inflammation of the gullet (oesophagus).
  • Piles (haemorrhoids).
  • Cancers of the bowel
  • Other rarer bowel disorders.

If you have one of these problems, you may have other gut symptoms such as stomach pains, constipation, or diarrhoea. However, in the early stages of these conditions, you may not have any symptoms and anaemia may be the first thing that is noticed. For example, IDA in an older person may be the first indication that bowel cancer has developed.


Some medicines can sometimes cause bleeding into the gut without causing symptoms. The most common example is aspirin. Other anti-inflammatory painkillers such as ibuprofen, naproxen, and diclofenac may also have this side-effect in some people. (Anti-inflammatory tablets may cause bleeding by irritating the stomach lining which may then lead to bleeding.)

Bleeding from the kidney

A small but regular trickle of blood from various diseases of the kidney or bladder, may not be noticed in the urine. However, enough may be lost to cause anaemia.

Dietary factors

Not eating foods with enough iron is sometimes the cause of IDA. This is uncommon in the UK as iron is in meat, liver, green vegetables, flour, eggs and other foods. Some people who have a poor diet with just enough iron to get by, may slip into anaemia if other factors develop. For example, a barely adequate diet combined with a growth spurt in children, or with a pregnancy or with heavy periods may lead to anaemia.

A restricted diet such as a vegan or a limited vegetarian diet sometimes does not contain enough iron.

Traditional diets in some parts of the world contain a high level of chemicals such as phytates and polyphenols. For example, certain types of flat breads (such as chapatis) may contain a high level or phytates. Tea can contain a high level of polyphenols. These chemicals interfere with the way iron is absorbed from the gut. So, if you eat a lot of these foods, it can lead to iron deficiency. For example, IDA is common in parts of India where chapatis are a staple food.

Hookworm infection

This gut infection is the most common cause of IDA worldwide. It affects people living in (or visiting) certain tropical countries. The worm feeds off blood inside the gut.

  • Common symptoms are due to the reduced amount of oxygen in the body. These include tiredness, lethargy, feeling faint and becoming breathless easily.
  • Less common symptoms include headaches, irregular heartbeats (palpitations), altered taste, sore mouth and ringing in the ears (tinnitus).
  • You may look pale.
  • Other symptoms may develop, depending on the underlying cause of the anaemia (see below).

Possible complications

Complications may develop if the anaemia becomes severe and is not treated. For example, you can develop fragile and broken nails, hair loss and heart failure. A lack of iron can also affect the immune system so you may become more likely to develop infections.

Anaemia in pregnancy increases the risk of complications in both mother and baby. For example, there is an increased risk of having a low birth-weight baby, preterm (premature) delivery and postnatal depression. Low iron reserves in the baby may also lead to anaemia in the newborn baby.

A blood test can confirm that you are anaemic. A test called the full blood count (FBC) is the main test. For this test, the blood sample is put into a machine which automatically:

  • Counts the number of red cells, white cells and platelets per ml of blood.
  • Measures the size of the red blood cells and calculates their average (mean) size.
  • Calculates the proportion of blood made up from red blood cells (the haematocrit).
  • Measures the amount of haemoglobin in the red blood cells.

This test can determine if you are anaemic. It usually also gives a good idea of the cause of the anaemia. But there are so many different causes of anaemia, the FBC cannot always help your doctor to know what the problem is.

You may need another blood test to confirm that the cause of the anaemia is due to lack of iron. This blood test measures a protein called ferritin. The level of this protein usually reflects the total body iron stores. A low level usually indicates that you have a lack of iron. The test can be difficult to interpret if infection or inflammation is present, as levels of ferritin can be high then, even if you are lacking (deficient) in iron.

It is important to find the cause of the iron deficiency. The cause may be obvious in some people. For example, anaemia is common in pregnancy, and in women with heavy periods. In these situations, if you are otherwise well and have no other symptoms, then no further tests may be needed. However, further tests may be advised if the cause is not clear. Every case is different and your doctor will assess if you should have further tests.

Tests that may be advised include one or more of the following:

Iron tablets are usually prescribed to correct the anaemia. Your doctor may refer you to hospital to have iron given in a different way if your anaemia does not improve on tablets, or you find it difficult to take the tablets. Other treatments may also be advised, depending on the underlying cause. See separate leaflet called Diets Suitable for People with Anaemia.

Iron tablets

Various iron tablets and liquid medicines are available. Your doctor will advise on one. The length of course will depend on how bad the anaemia is. A blood test after a few weeks will show if the treatment is working. Drinking orange juice when you take your iron tablets can increase the taking up (absorption) of iron into your body.

When your blood level is back to normal, you should continue to take iron for at least three further months. This will build up your stores of iron in your body. Blood tests at regular intervals after that will ensure you do not become anaemic again.

Some people have side-effects when taking iron. These include feeling sick (nausea), an upset stomach, constipation, or diarrhoea. You should tell a doctor if side-effects are a problem. Don't stop the iron or the anaemia will not get better. Possible ways to reduce the problem with side-effects are:

  • Taking the iron tablets with meals. Food reduces the absorption of the iron and so you may need to take a longer course to correct the anaemia.
  • Taking a lower dose; but again a longer course will be needed to correct the anaemia.
  • Drinking plenty of fluids if constipation develops.

Iron tablets may make your stools (faeces) black. This is normal and nothing to worry about. However, it is sometimes confused with blood in the stools from internal bleeding, which can also make your stools black.

Remember to keep iron tablets away from children, who may think that they are sweets. An overdose of iron tablets can be very dangerous in children.

Further reading & references

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Patient Platform Limited has used all reasonable care in compiling the information but makes no warranty as to its accuracy. Consult a doctor or other healthcare professional for diagnosis and treatment of medical conditions. For details see our conditions.

Dr Colin Tidy
Peer Reviewer:
Dr Hannah Gronow
Document ID:
4392 (v42)
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