January 16, 2005
A1c (Glycohemoglobin, HgbA1c)
Question from Spokane Washington, USA:
About three months ago, I was diagnosed with pre-diabetes due to an abnormal GTT (Glucose Tolerance Test). I started monitoring my blood sugars and my meter (an Accu-Chek Advantage) tells me that they have been going up. They went up tremendously over the holidays, and fearing bad news, I bought a Choice A1c test, the type you do at home and gives you a quick result. It told me I was 6.2, or approximately running a 143 mg/dl [7.9 mmol/L] average. This was higher than the meter, but I had read that the A1c can be 10 to 15 percent higher than one might expect. I had a follow-up with the doctor and his laboratory tells him that my A1c is 5.3, or about an 102 mg/dl [5.7 mmol/L] average, much lower than the meter! In fact, this was lower than many of my most recent fasting numbers.
I believe that, until just about three weeks ago, I was suffering lows. I did test several times in the high 60s mg/dl [3.3 to 3.8 mmol/L], low 70s mg/dl [3.9 to 4.1 mmol/L], with symptoms on my home meter. However, three weeks ago that stopped and I now run from about 93 to 160 mg/dl [5.2 to 8.9 mmol/L] all the time. My fastings are generally over 100 mg/dl [5.6 mmol/L] and my post-prandials, however, are around 110 to 150 mg/dl [6.1 to 8.3 mmol/L]. I’m having problems right now, that, I am told, could be related to blood sugar problems. I certainly feel poorly much of the time. I lose weight rather easily where, before, I had to be careful. I am highly interested in trying to determine what is going on.
Why would the meter, the A1c and the at-home A1c disagree with each other in this way? It appears to me to be beyond just normal variance. It seems to me that there should be some semblance of agreement, not one extreme, the other extreme and somewhere in the middle. My doctor was unable to comment. What should I believe and base my own decisions on?
Answer:
First, the home test is not the most accurate test available. Other methods for performing the test are much more accurate. It is not correct to compare results from different methods. Second, the A1c gives you an indication of the average daily blood sugar over the three previous months. If you measure the A1c more frequently, there may be a lag in your result, compared to your home blood sugar monitoring. Finally, you tend to underestimate your average blood sugar, as compared to what the A1c measures. Remember, the A1c is an average of all blood sugars combined, before and after meals. I would suggest that with your home blood sugars rising, you need to get back to your physician and discuss additional forms of therapy. This might include metformin or other oral agents.
JTL
