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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 haemoglobin
of 9 to 11g/dl. If someone has narrowing of the
blood vessels to the heart, they too may get angina
at haemoglobin of this level. Some young fit patients
may be to manage with 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 practitioners nowadays tend to treat
a moderately low haemoglobin (below 11 or 12),
particularly if someone is feeling weary.
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