You've got an appointment with your GP or Endocrinologist coming up and they set you up for a Hemoglobin A1C test. You get it done and on the big day it is higher than you expected. Annoyed, you start thinking of how in the world was it so high when your finger sticks seemed decent or your Continuous Glucose Monitor (CGM) data looked pretty good. If you are like me, we start thinking of how we're going to explain this. Before the appointment starts you feel like your already on defense.
To begin with, let's review what an A1C actually is. According to the CDC, it is a blood test that measures your average blood glucose over the last three months. Specifically,
"When sugar enters your bloodstream, it attaches to hemoglobin, a protein in your red blood cells. Everybody has some sugar attached to their hemoglobin, but people with higher blood sugar levels have more. The A1C test measures the percentage of your red blood cells that have sugar-coated hemoglobin."
So what does this have to do with kidneys? First, if you have Diabetes there is a 1 in 3 chance that you have Chronic Kidney Disease (CKD is a complication of diabetes more accurately called Diabetic Nephropathy). Second, if you have CKD you could also have anemia. If your kidneys are not working well, they may not be making the red blood cells your body needs. The American Kidney Fund does a great job explaining the details of anemia. If your doctor hasn't told you that you are anemic, a quick look at any of your hemoglobin tests will indicate that if the numbers are on the low end. Even if you don't have CKD, you still could have anemia. One study of 200 patients found that 22% had anemia, and of those 41% had normal kidney function and in 27% the cause could not be determined.
But what does this have to do with your A1C? Studies show that anemia has an impact on A1C, and one study cautioned that anemia should be fixed before A1C results are used to guide diabetes treatment decisions. That study has links to other published studies reinforcing the point.
So as a patient, how do you explain this to your doctor when they inevitably say something like "your A1C is too high" or "you need to do better at controlling your diabetes." Yeah--that annoys me, too and if you're going to hunt bear, bring the big guns. Last month, I had a first appointment with a new GP and knew this conversation was coming. What I did was to do a little homework beforehand.
First, I got the results of my most recent A1C, hemoglobin (HGB) and red blood cell (RBC) tests. On April 30, 2021 my A1C was 8.6%. Ugh! My hemoglobin on June 16, 2021 was 9.7 (normal range is 12-17 g/dL) and the RBC was 3.13 (normal is 4.2 to 5.4 M/cmm).
Next, being a Dexcom CGM user I went into their Clarity online system and ran a custom report. I configured it to start on April 30 and going back 90 days so that the CGM data would match the same period the A1C was supposed to measure. I printed it out to take to the appointment.
One thing about CGM reports: I've found that a lot of my doctors are impressed with the technology and once they understand it they find it is a useful tool. A lot of specialists don't have the time to learn about it and that is where we can be our own best advocates. More than once I've carried a copy of the summary page when I thought glycemic control might be part of our conversation. By and large when I show it to them, explain how I use it to optimize control of my diabetes it helps reassure them that I am an informed partner in achieving the best possible outcomes we can achieve by working as a team.
I also printed out a couple of the articles listed above to give to the doctor. First to add some credibility to what I'm saying I wanted to send a signal that I'm relying on vetted, peer-reviewed information--not some Facebook charlatan. Second, with the way doctors have jammed schedules and also want to stay informed, I was trying to support him with both challenges.
When appointment day arrived, one of the first things the doctor said was "you need to get your A1C down." I replied, "Well doctor, I have CKD and anemia. That skews the A1C higher than what my Continuous Glucose Monitor data shows. The A1C is just one data point, but the CGM takes a measurement every 5 minutes which provides 25,920 glucose reading over the same 90 days. While my lab A1C was 8.6%, the equivalent A1C based on CGM data was 7.6%"
I didn't bother explaining the virtues of Time In Range (the emerging gold standard of glycemic control) or standard deviation or other statistics. Our time together is limited and my role is the patient getting care and not an educator. But in the end, I made my case, got the care I needed (for the most part) and hopefully impressed my doctor with the impression that I was an informed partner.
I hope this is helpful and that you don't need to actually need to use this.
Kindest regards,
-Tom
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