Hba1c not reflecting BG level tests

Same here. HBA1C is an average as I understand it. Which confuses me somewhat as if I always test at 10+ I must get some serious lows to average it out. Spike do the damage? I think my Dn's reluctance to put me on tabs is down to funding more than anything else

Hi Sooty

There is not a perfect correlation between average BG levels and HbA1c. It is a statistical best fit line


As you can see there are lots of outliers from this line. I do not know if that helps at all

Sweeps_yellow_friend said:

Thanks for that Shelly and Andrew. Now I'm rather confused by how low my HbA1c is!! I suppose I'll have to go with the medics and their low HbA1c beats high BG line. So far all associated test have been OK so will save myself some money and ease off on the testing

Click to expand...

Are you sure your HbA1c was 4% ? That is VERY low. It is at the low end for non-diabetics. Have you misread or misheard something? Or am I misunderstanding?

In my opinion your self testing numbers are more important. They are too high. Your HbA1c may be low for a number of reasons, but for sure it is not low due to low blood glucose levels, since your self testing shows they are not low.

The HbA1c test is done on plasma blood. Finger pricks are done on whole blood. There is a difference, and somewhere there is a chart showing the equivalent values, but I can't for the life of me find it. I'll keep looking.

Then there is the rate/amount of glycation, which differs from person to person. A low glycator will see an HbA1c that is lower than any amount of finger pricking will show. Similarly, a high glycator will have an Hba1c higher than expected from finger pricking.

Then there are differences in our red blood cells. Some people don't have enough, some people have too many, some people have small ones and some people have large ones. This also affects the HbA1c.

Nothing is an exact science.

EDIT found a chart http://www.diabetes.co.uk/whole-blood-readings-to-plasma-converter.html

Does the time you test make a difference?

@serenity648: Yes it does! Your glucose levels will be changing all the time according to how much glucose your body requires as fuel - but perhaps most obviously from immediately before you eat to after eating as food will generally cause some sort of rise - think filling up your body's petrol tank then driving it round on and off all day. You meter acts as your fuel gauge. Random tests can't really tell you very much as you're testing in isolation with nothing really to compare. Ideally you should do a fasting test when you wake up and then immediately before and 2 hours after eating. If you do these tests regularly you should begin to see trends/patterns emerging, and the pre and post meals ones will also tell you how you respond to different foods, so you can modify your diet to improve matters. But you can also test to see what exercise, illness, infections, stress, etc, can also do to your levels - depending on what you want to find out.

Robbity

4.1 does seem like a very low HbA1C result. Certain blood disorders - sickle cell and haemolytic anaemia - and some medications can artificially lower HbA1C results:

http://www.ngsp.org/factors.asp

http://www.medscape.com/viewarticle/722406_2

Sweeps_yellow_friend said:

Hi! Five years diagnosed as type 2, on Metformin (4) and Gliclizide (1). My Hba1c results have been assymptotically approaching 4 in all this time from WAY up. My last reading was 4.1. My health care team are very satisfied and suggest that I don't self test for BG level. Of course I do and always will but the thing is that my BG levels are 10 - 12 as a norm with very rare dips to 7 but also sgnificant time at 14 - 17!!! I understand that HbA1c and BG are measuring completely different things and that HbA1c integrates over a long period and BG is a spot reading. However, even when testing at 10 tests per 24 hrs I hardly ever drop below 9. I have done everything to ensure my testing is correct (new machines/test strips/calibration with solutions and healthy people). The clincher is that the professional levels (which I insist on having taken) are also high. Please don't tell me to stop obsessing, I just want to know which of these two indicators have most bearing on health issues (retinopathy/peripheral neuropathy etc)?

Many thanks

Click to expand...

I concur with you that something is amiss. Doing 10 tests a day, is a significant enough number of tests to be in the ballpark of the A1c number - assuming that was not an isolated day and you were barely testing the rest of the time..

It sounds as if you are saying your average should be least a 10 mmol/l (10-12 , as a norm, with rare dips to 7, or a more significant number at 14-17). That should give you an A1C in the ballpark of 7.2% Looking from the reverse side, an A1c of 4% should give you numbers averaging in the ballpark of 3.6 mmol/l. As an example, based on my averages (of ~400 tests over 90 days), I expected an A1c of 5.3% (based on average readings of 6.0). My actual A1c was 5.7% - definitely in the ballpark.

So, as others have suggested, double-check your A1c - are you sure you are being given the % measurement, and not the IFCC measurement (40) and shifting a decimal point to 4.0% because you were expecting a single digit number? It would still seem a bit off (an average of 6.7), but not nearly as far off as you are experiencing.

My other suggestion would be to check your meter. Mine gives me the ability to view an average over the past 30 days. Check and see if that is closer to what you expect from your A1c. (And, if that is based on fewer than 100 or so tests, test more - fewer than 3 tests a day is unlikely to be at all predictive of your A1c unless you are very strategically testing. I track all of mine - and, as noted, my prediction was based on 400+ tests, and was still off by 8% from what I expected (drat that dawn phenomenon - which kept me high during a period in which I was rarely testing.).