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Glucose measurement

I

Ian Purdie

Newbie
Messages
3
Type of diabetes
Don't have diabetes
Treatment type
Diet only
After a blood test at the hospital I was told that my HbA1c level was 45 mmol/mol, so, according to that figure. I was a moderate risk. I have been using a TEE2 instrument to measure the gluose level for about a year. This instrument measures in mmol/L, so I have to convert to mmol/mol. My calculation gave a reading of 36.1 which is 20% lower that the hospital reading. My readings are taken early morning, prior to any food/drink, whereas the hospital figure was taken 3 days later at 1.30 p.m.

Could this discrepany cause such a difference in the readings?
 
a single glucose measurement has nothing to do with hba1c. Hba1c reflects the average glucose value for 3 months.
 
Ian Purdie said:
After a blood test at the hospital I was told that my HbA1c level was 45 mmol/mol, so, according to that figure. I was a moderate risk. I have been using a TEE2 instrument to measure the gluose level for about a year. This instrument measures in mmol/L, so I have to convert to mmol/mol. My calculation gave a reading of 36.1 which is 20% lower that the hospital reading. My readings are taken early morning, prior to any food/drink, whereas the hospital figure was taken 3 days later at 1.30 p.m.

Could this discrepany cause such a difference in the readings?
Click to expand...
Hi Ian, you say youve been tracking your BG for about a year, has it consistently been around 36? Maybe note down your results and take them to your diabetic nurse or endocrinologist and maybe they can explain?
 
Hi Ian (from another Ian), and welcome to the forum.
As Zhnyaka just said, a spot Blood Glucose (finger-prick) reading is measuring something completely different to an HbA1C from a blood draw sample.
A measurement of 45 for an HbA1c isn't far into the 'at risk' or 'prediabetes' range, but it doesn't tell you how things are right now which changes several times per day as you eat/digest/exercise etc.
The best use of a BG meter such as a TEE2 (I have one of those), is for determining which food your body doesn't handle so well. These will be carbohydrates, but which carbs affect you most is unique to your body since we all have different gut biome, genes etc.
The way to test food is to measure just before eating and then again 2hrs after first bite. The 2nd reading should be no more than 2 mmol higher than the first one. If it is higher than that, then perhaps you should eat reduced portions of that food or find a substitute.

It was by testing like that, that I knew to change my breakfast from whole grain oat porridge to boiled eggs.
 
HbA1c measures the number of glycated red blood cells - those are the cells that have had a glucose molecule attached to them. Red blood cells live about three months, so the measurement can only go back so far. It's also a bit skewed towards recent weeks. The normal range for HbA1c (for non-diabetic people) is 38-42.

In contrast the fingerprick blood test meaures the amount of glucose in your blood at that instant. Because you can't test all the time (when you're sleeping, for example) and because everyone's blood glucose is potentially changing all the time in response to a range of things - of which food is usually the most significant - it's next to impossible to estimate what your A1c is likely to be based solely on results from fingerpricks. There's a similar problem with a constant glucose monitor - it doesn't test blood, but uses interstitial fluid - and while it gives you information you can't get any other way it doesn't seem to be a reliable A1c predictor.

I tried the "averaging" method from fingerpricking myself just after my diagnosis, and based on calculations was predicting an HbA1c of 30. The eventual A1c was in the end more than satisfactory, but a good bit above 30. So the fingerprick tests were indicating my direction of travel was OK, but not to the extent of being able to forecast the next HbA1c.
 
Can I post a overall thank you to the various respndents. I found the information very useful and appreciate the time and effort taken in your replies.
 
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