A1C Discrepancies

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After I graduated college, my blood sugars weren’t under the best control.  This was before the continuous glucose monitoring technology was around and I only tested my blood sugar a few times a day (i.e. twice a day probably).  Back then, my A1Cs hovered in the 8’s.  Not terribly bad but not great either.  When I would go to see my endocrinologist, she would look at my poorly recorded log book and tell me that she couldn’t do much with the limited data I provided her.   Usually, she was mad that my A1C wasn’t below 7 but yet she couldn’t help me because I didn’t provide her enough information on changes we could make to my basal or bolus rates.

However, one visit I got my blood work back and my A1C was in the 7’s!  I couldn’t believe it and neither could my doctor.  My bad record keeping didn’t reflect an A1C that good since my blood sugars were usually hovering in the 200’s.  Reviewing blood sugars from finger pricks and what I had written down didn’t reflect an A1C in the 7’s.  To this day, I still question whether that A1C was accurate.

Which brings me to today.  Besides that one A1C about 10 years ago, I have never questioned an A1C.  Thanks to my CGM data and the Carelink software from Medtronic, I can log on and see my 12 week average which usually corresponds perfectly with my A1C result.  This “test” is usually very reliable for me so my A1C result is not usually a surprise.

Back in October, I had my blood work done and I was expecting my A1C to be around 7.  Based on my CGM data, my 12 week average glucose reading was 155.  I was pleasantly surprised with this number because I didn’t think I was doing that great a job balancing diabetes with motherhood.  Even though my 12 week average didn’t correlate with the A1C I was expecting, I didn’t question it too much because I did go some days without wearing my CGM and the weeks leading up to the blood work were better than the beginning of the three month period.

Last Friday, I had my endocrinologist appointment and got my blood work done.  Recently, I have been experiencing a lot of lows, mainly thanks to a GI virus I had for a week.  I have also been working with my CDE again and really working hard to get good basal and bolus rates, after about a year of letting my diabetes care take a back seat to everything else in my life.  My two week average was actually 112! My four week average was almost as good at 118.  My 8 week average was slightly higher at 127 but that still translates into a 6.02 A1C.  I was feeling pretty optimistic that I was going to have a GREAT A1C result.  I did still have a good A1C result but it wasn’t as good as I was expecting.

Yesterday, I got the result that my A1C was 6.5 again.  Pretty great but I was shocked because my blood sugars have been so much better recently than they were three months ago. If you look at the two graphs of my range of blood sugars over the two different time periods, the most recent graph shows blood sugars MUCH better than three months ago.  However, the average of 137 does translate to an A1C of 6.4, which is pretty close to 6.5, leading me to think that maybe my A1C back in October was wrong.

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Three months prior to October blood work

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Last three months, clearly better

Thankfully, I can keep a pretty decent gauge on my diabetes care with the CGM data and Carelink software but it does make me question somewhat how accurate the blood work is.  I would think its always very accurate but I wonder what could have happened in the two instances where I got better results than I was expecting.  Have you ever had an A1C that you questioned?  I guess I didn’t question them enough to have blood work done a second time but if it had been in the opposite direction (a worse A1C than I was expecting) I might have.

Amazing what a stomach virus can do for your blood sugars when you can't eat-last two weeks! Beautiful :) A1C

Amazing what a stomach virus can do for your blood sugars when you can’t eat-last two weeks! Beautiful and should be an amazing A1C!


3 thoughts on “A1C Discrepancies

  1. You are definitely dealing with a lot of overlapping margins of error – cgm data vs. “true” fingerstick (doesn’t help that some meters are allowed to be up to 20% off, in turn throwing off calibration of cgm, etc.) *eyeroll . Also from what I understand, there are several different A1C tests (with theit own error margins appended…) Also, there are situations in which te A1C is inaccurate (e.g. In pregnancy; apparently the hemoglobim molecule *changes (according to my endo) lol) in any case, a 1-month average of anything close to low 100s sounds like a sound accomplishment! 😀

    • Ah yes, you are definitely right! Tons of margins of error! I guess I just wanted to see some improvement since my blood sugars have been way better this past three months than the previous three months. Oh well, hopefully next time I will see some improvement especially if my blood sugars continue to be this good (but I think I only have the GI virus to thank for that haha).

  2. I was once at an appointment where they checked my a1c and I just knew it was too low based on what my blood sugars had been the past 3 months. I voiced my concern to my doctor who agreed and surprisingly had them test it again just 30 min later. There was a .4 difference between the 2 numbers which is actually quite a big difference for me. It was very strange. I have a post about it: http://typeonederful.com/2014/05/23/a1c-accuracy/

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