Passing the HbA1C test

I think the first site is American - they measure slightly differently.

It's confusing - for our meters in the UK the readings are measured in mmol/L, and these figures will look like 6.5. In the USA their meters use mg/DL and the figures will look like 120. These measurements are the actual levels at the time we prick our fingers.

Our HbA1c tests are an average of the amount of glucose retained in our blood over the past 3 months. In the UK our results are measured in mmol/mol and will look like 48; they used to be measured in percentages (so 6.5%), which were changed, I believe, because the figures looked similar to our meter reading but were quite different and could therefore be confusing/misleading.

The main diabetes.co.uk site has a whole section on this information which will give you more detailed technical information and various calculators and converters for the different types of readings and unit.

Robbity

DiabetesDaily is the other website I post on as there seem to be more US members on that site (not that that matters really).

As @Robbity mentioned, we measure differently here in the US. For basic glucometer readings we measure in mg/dl. The easy conversion is to multiply by 18. So a UK a reading of 5mmol/l would be 90mg/dl.

A1c results are measured in percentages as was also mentioned. I post on this site pretty regularly so I know the conversions pretty well. Even still, there are plenty of different units and measurements to remember and I agree it can be confusing at first.

Kyi said:

For example if you have an average 7 mmol reading you get a 6 A1c.

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That's not entirely true. Yes, there is a strong correlation between average blood sugar and a1c levels, but there are other factors that can affect a1c levels. That's why there is some variance between the charts you're seeing (if I understand your question correctly).

Volatility is another very important variable. For example, two people may both have an average blood sugar of 8mmol/l. However, if one generally fluctuated between 7-9mmol/l while the other fluctuated between 4-12mmol/l it would be highly likely that the person with tighter control (7-9) would have the lower a1c.

TorqPenderloin said:

That's not entirely true. Yes, there is a strong correlation between average blood sugar and a1c levels, but there are other factors that can affect a1c levels. That's why there is some variance between the charts you're seeing (if I understand your question correctly).

Volatility is another very important variable. For example, two people may both have an average blood sugar of 8mmol/l. However, if one generally fluctuated between 7-9mmol/l while the other fluctuated between 4-12mmol/l it would be highly likely that the person with tighter control (7-9) would have the lower a1c.

Click to expand...

There have been a few studies looking at this, and they have determined that variability doesn't get reflected in Hba1C, so as a measure of someone's optimisation of their blood glucose levels, they are a very blunt tool.

HbA1c correlates significantly with Average Glucose, post-prandial glucose and Hyperglycaemia in type 1 diabetic patients.

http://care.diabetesjournals.org/content/26/10/2728.full.pdf

Horribly small and short study => http://www.ncbi.nlm.nih.gov/pubmed/22466072

It may of interest to note that for someone who was recently diagnosed with T2D @HBA1C 11% and subsequently normalized it to 5.3% over 6 months...post meal glucose can still easily spike over 180mg/dl or 10mmol/L on a carb heavy meal.

So that would give some idea that a "normal" HbA1c reading of < 5.5% can be misleading. It does not correctly reflect the beta cell dysfunction/damages.

I've found that my 3 monthly average glucose readings give me a fairly close but slightly lower prediction for my HbA1c results. My levels are fairly stable overall but I'm assuming that the difference is due to the fact that I don't always see any bigger spikes I may get outside my normal morning, pre & post meal testing times. I assume that my Freestyle Libre might give more accurate predictions, but it's consistently giving me lower results than my meter - although the last sensor is closer to what my meter's telling me than the first two were.

@Kyi As I said in my original post our UK HbA1c results now use different units because of the confusion between our meter's mmol/L units e.g 6.5 mmol/L and the original HbA1c percentage (%) measurements e.g. 6.5% figures.
(However I believe that some UK people may still be given their results as the old percentage figures.) They're not the same, although they may sometimes look similar...

A while back I did a comparison post for someone of what identical numbers meant for all the various units, but it taxed my brain too much to ever wish to work it all out again!

Robbity

Found the bit in the post I was referring to above:

• our meter figures: e.g. 6.2mmol/L
• HbA1c percentage: e.g. 6.2% is the result of an average glucose level from meter readings of 7.3mmol/L
• HbA1c (average of 6.2mmol/L): gives results of 5.5% or 36.7mmol/mol,
• and a figure of 6.2mmol/mol would give you an average meter reading of 1.7mmol/L which would have you in serious trouble to put it mildly!

Robbity