Endocrinology and Diabetes
A1C Levels Why measuring Hemoglobin A1c levels is an indicator of blood sugar levels (and diabetes)
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- If a doctor's concerned if a patient has diabetes or is at risk for diabetes
- they might suggest an A1C test to be performed
- What I want to do in this video is to 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 is this to do with diabetes?
- 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 a red blood cells
- you have hundreds and millions of haemoglobin molecules, or haemoglobin proteins
- So let me draw some haemoglobin proteins
- Actually we have, the number I found is, 200-300 million per red blood cell
- and then we have tens of trillions of red blood cells, so we have a lot of haemoglobins in us
- and haemoglobin is what makes red blood cells red
- When haemoglobin is bound to oxygen, it has a red colour
- This right here, each of those are haemoglobin proteins
- Now, it turns out, a haemoglobin, let me draw a bigger version of it... haemoglobin
- If it has some glucose around, so let me draw some glucose floating around near the haemoglobin
- If it has some glucose around, there's some chance
- it's not a high probability, but there's some chance
- that the haemoglobin and the glucose bump into each other
- at 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 haemoglobin
- Now this haemoglobin with the glucose bound to it, is called "glycated haemoglobin"
- I wrote "glycated" in green, 'cause I'm using green for the glucose
- Another name for glycated haemoglobin, or haemoglobin that has some glucose bound to it
- is "haemoglobin A1C"
- And now I can imagine things are starting to click in your brain
- When you're measuring your A1C level, that's a test of the percentage of your haemoglobin that is haemoglobin A1C
- So you take a blood test, they're measuring relative to the total amount of haemoglobin
- what percentage of that is haemoglobin A1C
- And a normal range of that, so if just have normal blood sugar for a reasonable amount of time
- you're going to have a haemoglobin A1C level in kind of a 4-6% range
- And people are still kind of trying to tighten up this range
- and it doesn't completely correlate tightly with the blood sugar
- Well, it does correlate, but still, people of the same blood sugar can still have fairly different A1C levels
- But 4-6% is considered normal
- And if you have higher, higher than 7 or 8%
- so greater than 7 or 8%, so if you have like an A1C level of 9 or 10%, that's high
- 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 haemoglobin
- so you're going to have a higher percentage of haemoglobin A1C
- And the other reason why this is useful is kind of, well I guess you can see on the first pass
- it's useful because not one of these snapshots that test
- 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 through out the day
- changes depending on how active you are
- 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 where the blood sugar is through out the day, unless you just kept sampling
- which can get pretty annoying, you know, keep pricking your needle
- With A1C, this starts to become a measure of how much glucose you've had in your blood
- over a longer period of time
- And in general kind of uses for a measure for the last few months
- because the red blood cells and the haemoglobin in them
- they have a life span of about 120 days
- That obviously doesn't mean all of your haemoglobin gets produced on one day and all dies 120 days later
- you have some red blood cells and haemoglobin 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 around 60 days old, or about 2 months old
- So on measuring this percentage, you're definitely not getting the percentage of anything older than 120 days
- and on average you're seeing things that are from about 2 months old
- So the higher this percentage, this is saying:
- Wow, this is, you know, my average haemoglobin molecule in my body is only maybe 60 days old at this point
- And already 7-8% of them have already been glycated
- which is an indicator that I probably have more blood sugar than a normal person
- In normal situation, only 4-6% of my haemoglobin would get glycated
- so hopefully that explains what A1C is
- But I do want to say, and I said in the beginning of the video, that I'm not a doctor
- and even amongst doctors, the A1C test, or the A1C measurement
- 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've mentioned, two people with the exact same blood sugar could have different A1C levels
- depending on other things: how old they are, whether they have some other type of medical condition
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