May 25, 2007
A1c (Glycohemoglobin, HgbA1c), Complications
Question from Australia:
I recently had an A1c test done and the result was 5.2%. My blood sugars are usually from 5 mmol/L [90 mg/dl] to 17 mmol/L [306 mg/dl]. On average, I have four lows a week. I test six to 10 times a day, sometimes less than six. My meter averages are 10.4mmol/L [187 mg/dl] for seven days, 9.9 mmol/L [178 mg/dl] for 14 days, and 8.4 mmol/L [151 mg/dl] for 30 days. My endocrinologist looked over my log book and expected my A1c to be higher. She then had a look over some other test results and was almost positive than my low blood count/anemia is causing my A1c to be falsely low/unreliable. She also said my frequent highs are doing damage and that my lows are also probably canceling out some of my highs.
I don’t understand this. If I do have a “falsely” low A1c and am having highs, would these highs not do any damage anyway because of the low blood count and low A1c?
The use of the Hemoglobin A1c test to determine average daily blood sugar over three months is dependant upon the circulating time of the red blood cells. If you have anemia and a shortened red blood cell survival time, the hemoglobin A1c test does not accurately reflect your average daily blood sugar over the previous three months. Rather, it will under report your average daily blood sugar. This is a technical aspect of the test result. The separate question of why you are having damage from high blood sugar is particular to diabetes itself. When you have the high blood sugars, this is what causes the metabolic derangements in tissues that cause complications. Lows do not cancel out the effect of the highs. In fact, when you have frequent lows, these are commonly associated with rebound highs after you eat something to turn around the low sugars. Some researchers believe that the marked changes from high to low and low to high are more damaging than sugars that remain moderately elevated. Please be sure to follow with your doctor. Getting rid of the lows as a first step is always a good step in the right direction. Keep doing your monitoring. It will help you decide if you are going in the right direction. Work with your doctor to get your anemia treated. If it is reversible, it may allow you to use the hemoglobin A1c test in the future, although it may not be a good test right now.