Haemoglobin

Haemoglobin is the coloured pigment inside red blood cells that carries oxygen round the body. Haemoglobin levels in the blood are measured in grammes per 100 millilitres, which is abbreviated to g/dl. The normal range of haemoglobin for a man is 13.5 to 17.5 g/dl and for a woman is 11.5 to 15.5 g/dl. Anything less than these numbers is called anaemia. As the haemoglobin level starts to fall, the body is very good at compensating for the drop in red cells. The heart will beat faster and more forcefully and the lungs increase the amount of air they move each minute to increase the amount of oxygen they deliver to the blood. The body also gets better at taking up oxygen into the red cells and releasing it where it is needed. This is why we can often cope with slightly lower than normal haemoglobin levels, especially if they develop gradually. But when the level drops too low for us, we start to feel tired, breathless and may start to run into problems with too little oxygen getting to important organs like the heart and brain. This can cause palpitations, angina (chest pains), headache or dizzy spells. Not everyone will get symptoms at the same level. Some elderly people, whose heart and lungs are less good at compensating for their anaemia, may develop severe symptoms at around a haemoglobin of 9 to 11g/dl. If someone has narrowing of the blood vessels to the heart, they too may get angina at a haemoglobin of this level. Some young fit patients may be to manage with a much lower haemoglobin and only develop symptoms when their haemoglobin falls to around 6g/dl. However recent studies have shown that most people feel less tired if their haemoglobin is above 12g/dl. There is also some evidence to suggest that people may respond better to chemotherapy if their haemoglobin is at higher levels. As a result many doctors nowadays tend to treat a moderately low haemoglobin (below 11 or 12), particularly if someone is feeling weary. To some extent it is a matter of finding the haemoglobin where you feel most comfortable but severe anaemia is not safe and always needs to be treated. Often this will involve a simple blood transfusion which can rapidly correct the problem. It is also possible to correct your haemoglobin by giving a chemical called Erythropoietin. However this takes a long time to work, is not effective in everyone and requires regular injections. It is also very expensive.