now the next aspect of glucose
physiology we want to talk about is
glycolated
hemoglobin or sometimes called
glycosilated hemoglobin it means the
same thing but as you know the
hemoglobin is present in the red blood
cells so here we have a red blood
cell it's darker on the
outside lighter on the inside because
it's a biconcave
dis and this red blood cell is going to
contain hemoglobin that's why the red
blood cells are
red and if there's glucose in the
blood then some of that glucose is going
to diffuse into the red blood
cell and what happens is the glucose
becomes attached to the hemoglobin and
when there's glucose attached to the
hemoglobin that's called glycolated or
glycosilated
hemoglobin and the amount of sugar in
the blood is proportional to the amount
of hemoglobin which becomes
glycosilated so if the amount of glucose
in the blood is relatively low then
we're going to get relatively low
amounts of glycolated
hemoglobin but if the amount of glucose
in the blood is relatively High then
we're going to get relatively large
amounts of hemoglobin and this is the
basis of the
HB A1 C test HB of course is
hemoglobin and the A1C is to do with a
bit of hemoglobin which is
glycolated now you might remember that
red blood cells live for about 120 days
in the circulation that's about 17 weeks
so they're actually hanging around for
quite a long period of time and once the
sugar once the gluc glucose gets into
the hemoglobin it doesn't get out again
it's fixed so if you actually look at
the hemoglobin that's glycolated that's
actually giving you an average of the
blood sugar levels over quite a long
period of time so the reason the
glycolated hemoglobin test is so useful
is it's giving an average of the amount
of glucose in the blood over a period of
time and the amount of time it's giving
you an average over is around about 8 to
12
weeks so that test I did on my finger
when I just pricked my finger that tells
you what your blood sugar is now but the
glycolated hemoglobin using the hba1c
test gives you an average of blood sugar
levels over 8 to 12
weeks and this is useful for two reasons
firstly if someone has an elevated
hba1c that might mean there a diabetic
who has not been
diagnosed and this is particularly the
problem in type 2 diabetes someone can
have it for months or years without
being diagnosed but if there's an
elevated
hba1c that's telling you a lot of their
hemoglobin is glycosilated or glucal and
that's telling you that the average
blood glucose blood glucose levels on
average have been high over a period of
time and if the blood GL glucose
levels are high enough to gluc calate
the hemoglobin up to the point of 48 mes
per
mole then that patient is diabetic this
is a diabetic threshold now what does
this
mean well this means that there's 48
milles of glucose that's the number of
glucose
molecules 48 milles of
glucose per mole of
hemoglobin
so it's 48 milles of glucose per mole of
hemoglobin it's the amount of glucose in
a hemoglobin
molecule and that equals about 6.5% of
the hemoglobin being
glycosilated and actually at the moment
in the UK we're moving over to the mill
moles per mole Mill moles of glucose per
mole of hemoglobin rather than the
percentage but 48 milles per mole equals
6.5% now if someone's blood if someone's
hba1c if their glycosilated hemoglobin
is 48 milles per mole that is 6.5% or
higher that is a diagnostic criteria for
diabetes that means that patient
actually is in the diabetic range of
blood sugar
levels so greater than 6
.5% is diagnostic of diabetes and that's
48
milles per
Mo less than
6% that's
42 milles 6% is equal to 42 milles per
mole less than 6% less than 42 milles
per mole that patient is not diabetic
they're in a normal
range
but what about the range in
between what about 6 to 6.5% that is
what about
42 so
48% well this can be a pre-diabetic
level illustrating the patient has
glucose
intolerance so if the hba1 C is 6 6 to
6.5 that's 42 to 48 then that patient is
at risk of going on to develop diabetes
in the future it's a pre-diabetic level
of glycolated
hemoglobin