If a doctor is concerned that a patient either has diabetes
or is at risk from diabetes, they
might suggest an A1C test to be performed.
And what I want to do in this video is,
one, just explore what A1C even means,
and also how that actually relates
to diabetes, or the main side effect of diabetes, which
is having high blood sugar or hyperglycemia.
So to do that, let's think about red blood cells,
and I know what you're thinking, what
does this have to do with diabetes?
And we'll get there in a little bit.
So red blood cells are the main oxygen carriers in our blood,
they kind of look like these lozenges,
and inside of red blood cells you
have hundreds of millions of hemoglobin
molecules, hemoglobin proteins.
So let me draw some hemoglobin proteins.
You actually have, the number I found is 200 to 300 million
per red blood cell, and then we have
tens of trillions of red blood cells.
So we have a lot of hemoglobin in us,
and hemoglobin is what makes red blood cells red.
When hemoglobin is bound to oxygen it has a red color.
So this right here, each of those are a hemoglobin protein.
Now, it turns out that hemoglobin--
let me draw a bigger version of it--
if it has some glucose around-- so let
me draw some glucose floating around near the hemoglobin--
if it has some glucose around, there is some chance,
it's not a high probability, but there's
some chance if the hemoglobin and the glucose
bump into each other in just the right way,
that they'll bind to each other.
And so you'll have this situation
where you have glucose bound to the hemoglobin.
Now, this hemoglobin with a glucose bound to it
is called glycated hemoglobin.
I wrote "glycated" in green because I'm
using green for the glucose.
And another name for glycated hemoglobin,
or hemoglobin that has some glucose bound to it,
is hemoglobin A1C.
And now I can imagine things are starting
to click in your brain.
When you are measuring your A1C levels,
that's a test of the percentage of your hemoglobin, that
is hemoglobin A1C.
So you take a blood test, they're
measuring relative to the total amount of hemoglobin there,
what percentage of that is hemoglobin A1C?
And a normal range of that, so if you just
have normal blood sugar over a reasonable amount of time,
you are going to have a hemoglobin A1C
level in kind of the 4 to 6% range.
And people are still kind of trying to tighten up
these ranges, and it doesn't completely
correlate tightly with the blood sugar, it does correlate,
but people with the same blood sugar
can still have fairly different A1C levels, but 4 to 6%
is considered normal.
And if you have higher than 7 or 8%, so greater than 7 to 8%,
so if you had like an A1C level of 9 or 10%, that's high.
And so you can imagine, this is kind
of a proxy for how much glucose you have in your bloodstream.
Because the more glucose you have in your bloodstream,
the higher the probability that that glucose
is going to react with the actual hemoglobin.
So you're going to have a higher percentage of hemoglobin A1C.
And the other reason why this is useful,
and it's kind of, I guess you can see on the first pass, it's
useful because it's not one of these snapshot tests.
Everything we've talked about so far with respect to diabetes
is taking your blood sugar at any one point in time,
and we know that your blood sugar changes
throughout the day, it changes depending
on how active you are, it changes depending
on what you might have just eaten.
So when you do blood sugar, you're just getting a sample,
you don't know what the blood sugar is throughout the day,
unless you just kept sampling it, which could get pretty
annoying, keep pricking your needle.
With A1C, this starts to become a measure of how much glucose
you have in your blood over a longer period of time.
And, in general, it's kind of used
as a measure for the last few months, because the red blood
cells and the hemoglobin in them,
they have a lifespan of about 120 days.
Now, that obviously doesn't mean that all of your hemoglobin
gets produced on one day and then all dies 120 days later.
You have some red blood cells and hemoglobin
that might be a few seconds old, and then you
have some that might be approaching 120 days old.
So on average they're going to be about 60 days old
or about 2 months old.
So when you're measuring this percentage,
you're definitely not getting the percentage of anything
older than 120 days, and on average you
are seeing things that are from about two months old.
So the higher this percentage, this is saying, wow,
my average hemoglobin molecule in my body
is only maybe 60 days old at this point, and already 7 to 8%
of them have already been glycated,
which is an indicator that I probably have more blood
sugar than a normal person.
In a normal situation, only 4 to 6% of my hemoglobin
would get glycated.
So hopefully that explains what A1C is.
But I do want to say, I said at the beginning of the video,
I'm not a doctor, and even amongst doctors, the A1C test
or the A1C measurement, it's a little bit,
there's some debate about how useful it is,
what it's measuring, or kind of how far back it actually
is a good view at kind of your glucose levels.
And also, as I mentioned, two people
with the exact same blood sugars could have different A1C levels
depending on other things.
How old they are, or whether they
have some other type of medical condition.