Every cell in your body needs energy to do its job, which is obtained through oxygen. Oxygen enters the body via the lungs from where it is absorbed into the bloodstream. In the blood it is combined with a molecule called haemoglobin and then carried in red blood cells. This is a large molecule, mostly made up of protein with some iron in it. The oxygen weakly combines with the iron and is released when it gets to a part of the body where it is needed.

If there is less haemoglobin than is needed in the blood then a person is said to be anaemic.

If the body is short of oxygen, one of its responses will be for the kidney to produce a chemical called erythropoietin. This chemical tells the bone marrow to produce more red blood cells.

How Would I Know if I Was Anaemic?

If there is a sudden drop in the levels of haemoglobin in your blood, for instance, if you lose a lot of blood, you might notice that you tire more than you normally would and that you get out of breath quicker too. This is because when a healthy person gets out of breath, it is due to the fact that they cannot get enough oxygen into their body, so they breathe faster. When you are anaemic, because your blood cannot carry as much oxygen, your heart and lungs have to work harder to get that oxygen to the places where you need it. This means you get out of breath faster than you normally would.

Some people only find out that they are anaemic when they have a blood test for another, initially unconnected, medical reason. This is because if you're only slightly anaemic you might not feel any symptoms at all.

Why Might I Become Anaemic?

If someone has become anaemic, it is important to find out what is the cause. There are many different reasons; some are signs of serious illness and some are not. One of the first steps in finding out the causes of the anaemia is to find out what size the red blood cells are.

Iron Deficiency

If you aren't eating enough iron in your diet then you can become anaemic. Iron is recycled in your body and you only need to eat a little (unless, of course, you are losing iron). If you are a woman, you will lose iron when you have your period, so a woman needs more iron in her diet than a man.

Vitamin B12

This is a vitamin that is essential for the functioning of red blood cells. It is found naturally in meat and dairy foods. In theory, vegans could become deficient in vitamin B12, but since it is added to many other foods as a supplement this very rarely happens. The most common cause of someone being deficient in vitamin B12 is if the body's immune system attacks the cells in the stomach that absorb vitamin B12. This is known as Pernicious anaemia.

Some people who drink a lot of alcohol, find that they are eating less, as they get most of the calories that they need from alcohol. However, they do become deficient in vitamin B12 and iron.

An overactive thyroid can also cause a person to develop anaemia, though it would also cause other symptoms as well. In fact, almost any chronic disease can lead to an element of anaemia.

If Not Enough Red Blood Cells Are Being Made...

... then anaemia will follow. One of the reasons why this might happen is if there is something wrong with the bone marrow, such as myelodysplasia, a condition where the bone marrow cannot produce effective blood cells. Or it could be a problem with the kidney which detects when new red blood cells are needed.

Blood Loss

Losing a lot of blood is a common cause of anaemia. This can happen quickly, such as a large bleed, or over some months if a small amount of blood is being continually lost. If a large amount of blood has been lost recently, the cells will be of a normal size. However, if the blood was lost some days ago then a large amount of new red blood cells will be made. As new red blood cells are larger than mature red blood cells, the average cell size will be increased.

There are a number of conditions where red blood cells are destroyed inside the body.

Other Causes

There are genetic conditions, such as sickle cell anaemia, where, due to a defect in one of the genes for the haemoglobin molecule, there is no oxygen attached to the haemoglobin. It then changes shape, making the red blood cell itself change shape, getting stuck in small blood vessels.

There is also a condition called hereditary spherocytosis, where, again, due to a defect in the gene that codes the red cell membrane proteins, red cells are produced that are spherical instead of the usual shape (a bi-concave disc). There is also a similar condition where the cells are elliptical. Both these conditions mean that the cells are a lot more fragile, so are destroyed a lot faster than they are produced.

Another genetic condition that affects red blood cells is a deficiency in an enzyme called glucose 6 phosphate dehydrogenase, which helps produce energy inside the red blood cell.

Sometimes the body's immune system forms antibodies against proteins in the surface of red blood cells. This can be induced by a variety of events, often an infection.

Some drugs used in the treatment of cancer can also cause anaemia.

How Do you Treat Anaemia?

That depends on the cause. If the anaemia is due to iron deficiency then you can take iron tablets which are available from any chemist. Of course, it is important to read the label if you are taking iron tablets as they can have nasty side effects. If someone is very anaemic, they might need a blood transfusion. If the anaemia is due to kidney failure then a drug called EPO can be given. This is a replacement for erythropoietin.