I understand the basic concept that it is a (averaged??) snapshot of prior 90 days of blood glucose levels… but what is the value (% or ppm, etc.) and how is it reached?
With a diabetic, glucose levels aren’t always stable. Let’s say you ranged from 150-350 on a given day…what value is given to that “day” in the 90 day picture?
In: 40
A1c is measuring glycation byproducts on your red blood cells. Sugar has a nasty habit of “caramalizing” things, it browns your tissue. As glucose comes into contact with your tissues and cells it can glycate them, damaging them. As this damage accumulates over time it can cause issues. In red blood cells the important part we’re looking at is hemoglobin. The iron containing molecule responsible for oxygen transportation around your body. It’s a percentage.
Your cells, no matter how well controlled your blood sugar is will always be attacked by glycation. That’s just the nature of having glucose floating around. As you have higher glucose the glycation byproducts increase. So the less well controlled your blood sugar the more glycation on your red blood cells. Higher blood sugar after a meal you’ll get more glycation, lower blood sugar fasting over night, less glycation during that time. And as you said, red blood cells stick around for *about* 3 months, this results in an average snapshot of your glucose control over that time span.
There’s some issues with a1c though. Certain phenotypes have higher red blood cell turnover than the average. This means that since the cells aren’t as long lived they are not subjected to the same glycation load over time resulting in an A1c that may appear normal even though their blood sugar is poorly controlled. And on the other end of the spectrum there’s now some cases being reported of carnivores having elevated A1c levels despite phenomenal insulin sensitivity and rock solid glucose levels. One explanation might be that due to their extreme metabolic health the red blood cells are simply living longer before the cell dies resulting in more glycation load due to their longer lifespan.
This actually happened to me over my time as a carnivore. My A1c was high as a pre-diabetic with poor blood sugars and high insulin resistance. It went phenomenally low as my insulin resistance improved. Then after a few years started to climb again.
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