Do recent highs impact A1C draws?

I’m looking for some opinions here.

If you have something more concrete than an opinion, that’s even better.

I have a story to share, but I don’t have time to post about it right now. But due to the events in that story, I had the first reading of “Hi” on my meter last night (that means over 500 I think, or is it 600?) Either way, I was super high. I’ll tell you all about it another time. I was able to catch it middle of the night, and correct, and woke up this morning at 167 mg/dl. Feeling a little tired, but overall, not too bad.

Then I went and had breakfast – and totally forgot to bolus for it. Doh!! So, I caught that one a couple hours later, feeling yucky, with a test result of 350 mg/dl. What the hell was I thinking about that I forgot to bolus?! That’s the first time in many, many months that I’ve forgotten. If it were more common for me, I would utilize the “Missed Meal Bolus Alerts” that can be configured on my Cozmo. I don’t use them, because it just doesn’t happen very often.

I have my endo appointment a week from tomorrow, and I need to get my labs drawn so he has the results in time for the appointment. I have tomorrow and Monday off from work, and had planned on getting the labs drawn and out of the way tomorrow.

But – will my recent episodes of really high readings somehow skew the results for the A1C test? Would it “buy” me anything by going on Monday rather than tomorrow?

What are your thoughts on this? Cast your vote! Thanks!

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14 thoughts on “Do recent highs impact A1C draws?

  1. I have been reading these comments with interest, as I had no expert medical knowledge to toss in the ring myself. I have learned a lot, though. 🙂

  2. My understanding of the A1C’s is the same as the other folks. It is an average for the last three months. So the recent highs should not affect the numbers as much.
    Also it is an attenpt at getting the averages. So some spikes or lows do not make that much of a difference.
    Good luck on your appointment.

  3. Scott and Bernard,

    Diabetes Care has been available online for several years. When you are at the Diabetes Care home page, scroll down to the bottom and you will see a list of other ADA diabetes journals that are online: Diabetes, Clinical Diabetes, Diabetes Spectrum, and DOC News. Click on those and it will take you to their home pages. I am not familiar with DOC News. It must have recently been added.

    When researching a particular topic instead of just looking for a specific article, click on advanced search at the top next to the boxes where you put all the article info and this will take you to a screen where you can search all the journals I just mentioned at the same time. For example, under title you could put continuous glucose sensor, leave everything else blank, scroll down a bit and select the journal you want or select all ADA journals.

    Each journal only goes back so far for full articles. For example, Diabetes Care goes back to March 1998 and before that only abstracts are available. Plus articles published during the past 6 months or so are not available online unless you have a subscription. But, of course, they will eventually be available when that six month time period is up.

  4. Hey

    I also found this interesting (technical) article on the Dexcom. Again at Diabetes Care.

    Title is (it’s a mouthful) Improvement in Glycemic Excursions With a Transcutaneous, Real-Time Continuous Glucose Sensor, and here’s the pointer to the full PDF for the article.

    Theresa, I didn’t know so much of Diabetes Care was readiy available.

    Thanks again,


  5. Thanks also Theresa

    It took me a while to get it.

    So to help others here’s a direct link to the PDF of the article itself.

    Let us know if there are any other ‘useful’ articles there.


  6. Thanks Theresa! That is a wonderful source of information that I was not aware of!

    I’m a bit too dense to comprehend all of the detail – but, as you suggested, the conclusion made it mostly make sense.

  7. Scott,

    Here is an article in the journal Diabetes Care at that you can look up for free. It is in both full text or PDF. Here is the article information to put in the search boxes:

    Derr, R. Is HbA (1c) affected by glycemic instability? Diabetes Care, vol. 26, pg. 2728-2733, 2003.

    The findings of the study as others have said here, is that your recent high bgs should not influence your A1c.

    If you don’t know anything about statistics, you may just want to read the discussion/conclusion of the article.

  8. Scott,
    When I was at AbtNW Hospital for my ketoacidosis episode, they did an A1C with the admitting bloodwork. Since this is a teaching hospital, I clearly remember discussing it with the chief resident and a dozen curious medical students circled around the bed. In essence, he said that no, the disastrous numbers that led to the episode would “contribute their share proportionately” to the AlC, but not “unfairly distort” it.

  9. I’ve always been told that results from the week immediately preceeding the test have a very negligible impact on the result because that fraction of haemoglobin is very unstable. Apparently this is what Ragnar Hanas teaches, so I’m definitely inclined to think there must be some truth in it. In this case, the sooner you get it drawn, the better.

    Either way, in the grand scheme of things, how long was blood glucose actually that high for? A few hours out of all the time in the last 2-3 months is nothing.

  10. This is something I’ve rambled about before, and to this day it still gives me headaches.

    My understanding is that A1c tests measure the amount of glucose that has attached itself to the outsides of hemoglobins (essentially, your red blood cells). Since each individual red blood cell has a life-expectancy of approximately 3 months, the single draw of blood when you go to get your test done has red blood cells of varying age, with varying amounts of glucose stuck to them. Thus, it’s an average measure in the sense that it’s a snap-shot of a single point in time of a dynamic process (both the life and death of red blood cells and the fluctuations of glucose we expose them to).

    So does it matter whether you wait 3 days to get your blood drawn? Unfortunately, that seems unlikely. Either way, you’re going to have a solid population of red blood cells exposed to that high dose of glucose. Some of them may be near the end of their lives and be dying off in the next few days, but the bulk of them will be there.

    I’ve read that the A1c is basically a weighted average of blood sugar control. 50% of the test result reflects you control over the previous month, 25% reflects control over the month before that, and the last 25% reflects the control over the month before that (though this seems like a ridiculous simplification of the hemoglobin life-cycle).

    Holy crap, I’ve rambled on! (my comment might actually be longer than your post!)

    So I’ll wrap it up on this high note (that’s a pretty good (and honestly unintended) pun, huh?): You thankfully caught that super high reading and brought it down quickly. I’m guessing the short period of time spent in the stratosphere likely won’t have too large of an effect on your overall reading. I think the rest of the time is much too large to be significantly affected by a few hours of highs. It’s when those hours start becoming days and weeks that you have to really worry.

    Note also, that this is largely based on a patch-work of reading and just my best guess as to how it actually works.

    Good luck, buddy.

    (Oh yeah, and I really like the possibility that there’s a significant lag in the numbers as Maura mentions. Though I imagine that will only really show up if you’re having some signficant changes in your daily regime and your meter averages are changing quickly).

  11. Hmmm… I would guess that in the scheme of things, over the course of three (or even one) months just one or two highs–even super high highs–wouldn’t be enough to make that much of a difference. I think it might make a little difference, but nothing significant. That is, of course, just my humble opinion.

  12. I would go sooner rather than later. I have been getting my A1cs done every month and I think there is a lag effect. When I think it will be really low, it isn’t until the next month. Maura