Yes - I know it is BSL readings but im interested in - *how far back does it measure. *Will just a few spikes affect the reading significantly. * Are the more recent BSL s the most important contributor to a reading? I know - it may seem a dumb question but Id really like to understand such an important measure of my health. THANKS.
Here’s my take on it: A few spikes will not effect it significantly. Assuming they are truly spikes, i.e., the BG level returns to something near normal pretty quickly. I spike frequently (semi controlled thru diet and Symlin) but keep an A1c around 6.5. So my anecdotal, but real life 4 year experience says spikes don’t effect it too much if you control them as much as possible.
Re how far back it goes - “The HbA1c level is proportional to average blood glucose concentration over the previous four weeks to three months. Some researchers state that the major proportion of its value is related to a rather shorter period of two to four weeks.” From Wikipedia and “Hemoglobin A1c Fact Sheet”. Michigan Diabetes Research & Training Center. Retrieved 2007-12-26
There are a variety of things that affect the HbA1c. Although on average red blood cells live 3 months, they don’t all live that long and different people have different red blood cell lives. The HbA1c will be affected by anemia or its antithesis polycythemia, often dramatically (check your hematocrit). Some people are thought to be low or high glycators (http://care.diabetesjournals.org/content/30/10/2756.full) resulting in a distortion of the HbA1c either up or down. Over time, you will get an idea about how your own HbA1c correlated with your meter readings. Expect there will be some ongoing difference since you will, as a diabetic, test at certain biased times (morning, before meals and after meals) which result in a sample that does not truly represent your average. My HbA1c has traditionally been overestimated my average blood sugar by 30% compared to my meter average.
As to the spike question, there is quite a bit of evidence that the glycation process is linearly proportional to blood sugar, so highs and lows will average out.
Yes, I absolutely agree. Over the years I have learned that the lows bring down the average high and vice-versa. Sometimes you have an almost normal A1c and are suprised because you can recall some highs but you have to consider the lows too. Its only a “number” for the doctors to make reference to because they are not with you on a day-to-day basis.
Thank you for your advice. Much appreciated. I had also heard that it was related to readings from the sorter term so thanks for this.
Sensible advice and has helped me get a clearer picture. Thanks.