Posted by on Thursday, 24 February 2011

'HbA1c phenomenon' and feeling grumpy

I have an annual review coming up in April. I know this because I called the hospital a while ago to check I was still on their list (I recently transferred back, having been seen at my GPs for a few years).

I also know it because my blood glucose levels have been running stupidly high recently. This seems to happen to me a lot. As soon as I know I'm in the 3 months running up to the test (HbA1c gives an indication of average BG levels over the last 3 months) it all goes to pot. I've come to think of this as 'HbA1c Phenomenon'.

I've been working hard at getting my diabetes under control for around a year now. When I look at monthly average figures during much of that time they are around 6.9 - 7.1 mmol/L. There's a ready reckoner which suggests your HbA1c if you give it an average BG level for 3 months or so, provided the tests include a decent spread of pre- and post-meal results (which mine now are). There are a fair few of these conversion formulae, but the one I use is:

HbA1c = (BG average+2.52)/1.583

Weekly averages recently have been in the mid 8's. I haven't been doing this badly for about 8 months. I was so hoping for a good A1c. Almost as an 'official' affirmation of the work I've been putting in. Secretly I think I was hoping I'd make it into the elusive 5% club (sub-40 in new mmol/mol numbers), but now I think I'll be lucky to match my last one of 7.1%. If I was still pottering along without paying much attention I'd be happy enough with that (as indeed I was), but when you are working much harder at something it's nice to see some sort of results, and a little frustrating to think that you would have seen those results a month or two ago when you didn't have the test scheduled!

In my heart I know that the HbA1c is a pretty poor indicator of control. I've cheated low numbers before by having enough hypos to cancel out all the highs. But it's the badge which defines you as far as the medical profession is concerned. However inaccurate it is, it's still considered the 'gold standard' indicator. I wanted not only to have better control (which I do) but to have a pleasingly low A1c to match.

So I am trying (and largely failing) not to get too grumpy about this. To breathe deeply, take one test at a time and be happy with how far I've come in the last 12 months.

You never know... the test is weighted to the most recent 4 weeks or so. I might still have a chance to knock a bit off if I can keep my head during March.


  1. Thank you! You have just changed my life!!!

    No one has ever given me a conversion formula like that, and I have been worrying that my averages have been too high for too long. But I've been equating average bg (roughly) with HbA1c, and basically thinking I really must change my lifestyle - and that's from a situation where I already seem to be managing bg to within a inch of it's (our)life!

    But your calc has set me free. Thank you so much.

    (Don't you think that measuring blood sugars is like good old fashioned homework? Good results feel like getting a good mark for homework. Great in their own, impartial, right, but somewhat belittling, even infantalizing, for the adult concerned. Complicated.)

    Thanks, anyway - you are my first diabetic blog, and it's helping. Cheers.

  2. Thank you so much for your encouragement Judith. It means a lot. I've still not had an HbA1c to see how the lab result compares with the BG average formula conversion. To be honest given the run of terrible BGs recently I'm quite glad about that!