HBA1C

Basically the average lifespan of a red blood cell is ~3months. Each RBC contains haemoglobin (Hb) that is responsible for carrying oxygen. However, glucose can also 'stick' to this. The HbA1c measures this 'stuck' glucose. Now, as the RBC lives ~3m you can get an average BG level that reflects 3m worth of control.

In animals we still tend to use fructosamine rather than the HbA1c; for lots of reason but mainly accuracy and costs are not beneficial for the latter.

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Some things like oxygen in your blood plasma bind well to the red blood cells. Carbon monoxide in your blood plasma bind even better to your red blood cells, which is why it is so dangerous. Other things like alcohol don't bind with your red blood cells and they stay in the plasma.

Glucose will bind with the red blood cells but not easily. Glucose in the blood plasma is up and down all the time, depending on what you eat or how much activity you undertake but as long as there is enough of it for a long enough time, some of it will bind with the red blood cells. Measuring how much has bound to your red cells gives a more stable indication of the glucose level precisely because it is not up and down as quickly as the blood plasma.

The measurements are different because blood plasma is a liquid whereas most of the red blood cells consist of solids. However, it is still not a perfect system of measuring because two people with similar readings for their blood plasma can still have very different readings for their respect HBA1c measurements.

lizdeluz said:

Can someone explain the % figure and the mmol figure?

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Your blood contains a huge number of haemoglobin molecules. You can think of each of these as a little bucket that carries a small bubble of oxygen around your body. Sometimes sugar "sticks" to these buckets. The more sugar in your blood, the more often this happens. The % figure counts what percentage of the buckets have a glucose molecule stuck to them. For instance if your HbA1c is 8%, that means 8% of the haemoglobin molecules in your blood have glucose attached to them. Since these buckets are recycled after about 3 months, your HbA1c tells you roughly how high your sugars have been, on average, over the last 3 months.

The "mmol/mol" figure is quite similar, it counts how many of the haemoglobin molecules (buckets) have glucose attached, per thousand haemoglobin molecules. (A 'mole' is a chemical unit that tells you how many molecules are in something.) However, new and improved testing standards are used to obtain the mmol/mol figure compared to the % figure, which is why the % figure is being phased out, and also why the conversion between % and mmol/mol is not a simple multiplication by 10.

lizdeluz said:

Also, what hb1ac should I be aiming for?

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The advice on this varies. The first thing to note is that a non-diabetic's HbA1c will be roughly between 4% and 5.5% (or 20 mmol/mol and 37 mmol/mol), although sources vary. The higher your HbA1c, the greater your risk of diabetic complications.

However, type 1 diabetics face the danger of hypos, and intense diabetes management is stressful and impacts quality of life, so HbA1c values of 6.5% - 7.0% (47-53 mmol/mol) are generally recommended as a good balance between hypo risk, complication risk, and quality of life. If you find it relatively easy to achieve better control, have good hypo awareness, and get few hypos, you may want to aim for a lower HbA1c. If you are having a lot of trouble managing diabetes, or have problems with hypos, you may want to aim for a higher HbA1c.

There's no shame in having a high HbA1c; some people's diabetes is just a nightmare through no fault of their own. But if you want to improve your HbA1c, there's a lot you can learn here and elsewhere that may help! I went on a low-carb diet and took my HbA1c down from about 6.9% to about 5.7%.

Thanks for asking this question.I'm lost with the numbers myself.There seems to be two scales of measurement and I've only grasped the % one so far.

sugartoohigh said:

Thanks for asking this question.I'm lost with the numbers myself.There seems to be two scales of measurement and I've only grasped the % one so far.

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There are actually more.

Two basic things are measured, blood plasma, ie the liquid and haemoglobin, the solids, the red blood cells. Blood plasma readings change all the time, every hour or even less, haemoglobin is more stable and acts like a sort of average. Because they are different things, they are measured in different units. Then we have the american way of doing things and we have our way of doing things. So, in we have 2 different measuring systems for each of the two things to measure. Then we have the old way of measuring the haemoglobin and we have the new way of measuring the haemoglobin.