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This leaflet provides a general overview of anaemia.

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 are released into the bloodstream each day. A constant new supply of red blood cells is needed to replace old cells that break down. Red blood cells contain a chemical called haemoglobin. Haemoglobin binds to oxygen and takes oxygen from the lungs to all parts of the body.

To make red blood cells and haemoglobin constantly, you need a healthy bone marrow and nutrients such as iron and certain vitamins which we obtain from food.

Anaemia means that:

  • 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.

  • Common symptoms are due to the reduced amount of oxygen in the body. These include tiredness, having little energy (lethargy), feeling faint and becoming easily breathless.
  • Less common symptoms include headaches, a 'thumping heart' (palpitations), altered taste, and ringing in the ears (tinnitus).
  • You may look pale.
  • Various other symptoms may develop, depending on the underlying cause of the anaemia.

Iron-deficiency anaemia

Lack of iron is the most common cause of anaemia in the UK. This is called iron-deficiency anaemia. If you eat a normal balanced diet, it usually contains enough iron. See separate leaflet called Diets Suitable for People with Anaemia for more details. The following are some reasons that may lead to a lack of iron and result in iron-deficiency anaemia:

  • Pregnancy or childhood growth spurts. These are times when you need more iron than usual. The amount of iron that you eat during these times may not be enough.
  • Heavy menstrual periods. The amount of iron that you eat may not be enough to replace the amount that you lose with the bleeding each month.
  • Poor absorption of iron. This may occur with some gut (intestinal) diseases - for example, coeliac disease and Crohn's disease.
  • Bleeding from the gut (intestines). Some conditions of the gut can bleed enough to cause anaemia. You may not be aware of losing blood this way. The bleeding may be slow or intermittent and you can pass blood out with your stools (faeces) without noticing.
  • If you eat a poor or restricted diet. Your diet may not contain enough iron.

Other causes

There are many other causes of anaemia. These include the following:

Lack of certain vitamins such as folic acid and vitamin B12. See separate leaflets called Folic Acid Deficiency Anaemia and Vitamin B12 Deficiency and Pernicious Anaemia for more details.

Red blood cell problems, such as thalassaemia, sickle cell anaemia and other causes of haemolytic anaemia. In these conditions the red cells are fragile and break easily in the bloodstream.

Bone marrow problems and leukaemia are uncommon; however, they can cause anaemia.

Other conditions such as rheumatoid arthritis and chronic kidney disease can also cause anaemia.

A simple blood test can measure the amount of haemoglobin in your blood and count the number of red blood cells per millilitre (ml). Although this test can confirm that you are anaemic, it does not identify the cause of your anaemia.

Sometimes the underlying cause is obvious. For example, anaemia is common in pregnancy and in women who have heavy menstrual periods. In these situations, no further tests may be needed and treatment with iron tablets may be advised. However, the cause of the anaemia may not be clear and so further tests may be advised.

Some causes of anaemia are more serious than others and it is important to find the reason for anaemia. The treatment of anaemia depends on the underlying cause. For many people this may simply be iron tablets. For others it may be a course of vitamins or other more complex treatments.

Further reading & references

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS 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.

Original Author:
Dr Tim Kenny
Current Version:
Dr Colin Tidy
Peer Reviewer:
Dr Hannah Gronow
Document ID:
4391 (v41)
Last Checked:
Next Review:
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