What are some reasons for a false low A1c? This is happening to a friend…not me.
Thanks
I’m a bit confused by the question. What makes your friend thinks her/his A1C is falsely low?
There are a number of reasons that a HbA1c would be distorted and give a false reading. One particular reason is anemia, it can cause a low reading. Also, some people are what they call low and high glycators and the HbA1c consistently comes in low or high. In my case, I’ve noticed a systemic error of about 20-30% between my average meter readings and the eAG that would be expected from my HbA1c.
I just went to one of those free screenings at my local pharmacy. I was shocked when they told me my HbA1c was 6.7. Of course they said that was good but my readings have been mostly under 100 with the exception of some 1 hour pp’s at 125 and 2 hour betwen 100-110. Now I am wondering if my meter is right. I switch between several Bayer Contour meter and they are all the same. I guess that makes me a high glycator.
If you meter is accurate, you would expect an A1c of about 5.5%. If they gave you the A1cnow, it is NGSP certified and at worst, it should be no more than 1% off. So it would be surprising to have such a variation. Low and High glycators tend to “always” run high or run low. Have you had previous tests be higher than anticipated?
An A1c is based on a three month period because that’s the average lifespan of red blood cells. Some people RBCs live longer or shorter. This can effect the result. I’m guessing that your friend believes her A1c is a false low based on her meter readings. Of course, meter margin of error is ±20% & throws another wrench into the accuracy game. Your friend may have lows overnight that she’s not aware of that might also account for her lower than expected A1c.
I think my HbA1c has always been higher than my meter readings but I always assumed it was due to DP. Lately though I have really tightened up my diet and eliminated most spikes. I even test often at 1 hour pp to pick up a spike and do random bg tests to see if I get spikes at other times of day. In the past 3 months I have had one wierd spike when I forgot to take my metformin. I do spike when I exercise but have cut back on exercise because of that. I now do mostly walking. I had high bgs last summer due to a bad reaction to prevarastatin with severe inflammation. I stopped the drug in middle of August, so that was 5 months ago. Could the red blood cells live that long. Lately I have added a few carbs like Eziekel bread back in my diet because I was losing too much weight on Bernstein. I think I am going to go back to Bernstein for a few months. Today fasting was 67. My lowest HbA1c was 5.9 last year and based on my meter readings it should have been around 5.0. Question, if I know I am a high glycator should I keep my meter readings in the 70’s most of the day as opposed to the 90’s.
If you know that you are a low or high glycator, I think it is better to “trust” your A1c less and look to your meter readings and other tests for an indication of how you are doing. I have usually had the fructosamine test taken to provide an additional datapoint, although the fuctosamine test also suffers fro certain distortions. In your case, you might confirm that you meter (or meters) are accurate. It seems surprising that you would run an actual fasting that low. In either case, a normal fasting according to Dr. B is 83 mg/dl. I was never able to get my fastings below 100 mg/dl with medications, I think it is amazing that you have gotten your levels down that low. I would think that running a fasting in the 90s would be quite adequate. Diabetes is all about finding the best control possible while still leading a happy and practical life.
I think too that you can get variance in A1C results compared to meter readings depending on when you test? If your testing paradigm is oriented towards those times when your BG will be higher, your A1C can run lower than you might expecct? When I started testing a lot more is when I noticed that while my 2 hour readings were ‘in range’ a lot of times the 1 hour readings were higher so the line was a bit different than I expected and probably explained how I could get a higher A1C than I’d hoped for? I could see that if you were looking for lows aggressively w/ your meter, you could skew things the other way?
I like having nice results but, other than suggesting a direction, A1Cs are useless for making the sort of tactically oriented moves you have to make to improve an A1C?
I think it’s important not to get too caught up in looking at online charts that show you what your average BG is based on your reported A1c. Those charts do not show the range of average BG possible given a reported A1c.
Here’s a chart from the ADAG (A1c Derived Average Glucose) study:
http://care.diabetesjournals.org/content/31/8/1473/T2.expansion.html
If you look at a reported A1c of 5.0, for example, that A1c represents a range between 76 and 120. These typs of ranges are typical for human beings. For all the reasons already given in this thread, you wouldn’t expect an A1c to represent a single average BG for every single diabetic.
It would be nice to know if we are low or high glycators and what our A1c actually translates inot as far as average daily BG goes but I think the best use of our A1c is to track our own progress. If our own number is going up or down, we can look at what that means for us. I think our own meter readings can fill in a lot of the blanks.