Iron deficiency anaemia occurs when there is a reduced number of red blood cells because the body does not have enough iron to produce them. The main symptoms are tiredness and lethargy (lack of energy).
There are several different types of anaemia and each one has a different cause. The most common type of anaemia is iron deficiency anaemia, which this article focuses on.
Other forms of anaemia can be caused by a lack of vitamin B12 or folate in the body.
See the Health A-Z topic about Vitamin B12 and folate deficiency anaemia for more information about this condition.
Iron is found in meat, dried fruit and some vegetables. It is used by the body to make haemoglobin, which helps store and carry oxygen in red blood cells (see box, left).
Haemoglobin transports oxygen from the lungs to the rest of the body. If there is a lack of iron in the blood, the organs and tissues will not get as much oxygen as they usually do.
How common is iron deficiency anaemia?
Iron deficiency anaemia affects up to 1 in 20 men and 1 in 20 post-menopausal women (after a woman's monthly periods have stopped).
Iron deficiency anaemia may be more common in women who are still menstruating (having periods). This is because menstruation and pregnancy can cause iron deficiency.
Treatment for iron deficiency anaemia involves taking iron supplements to replace the missing iron in the body. This is usually very effective and the condition rarely causes any serious complications.
If you have iron deficiency anaemia, you will need to be monitored every few months to check that the treatment is working and that your iron levels have returned to normal.
In some cases, further tests may be necessary to determine the underlying cause of your iron deficiency anaemia. In men, the most common cause is bleeding in the gastrointestinal tract (the stomach and intestines), which may require separate treatment.
Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.
Bone marrow is the soft, spongy tissue in the centre of bones that produces blood cells.
If you have a deficiency, you are lacking in a particular substance needed by the body.
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Plasma is the liquid part of blood, which holds other blood cells together.
The sac-like organ of the digestive system. It helps digest food by churning it and mixing it with acids to break it down into smaller pieces.