A1C is still the norm for doctors or Hospitals although they are beginning to hear about time in range.
A1C is very problematic as it is an average of blood glucose over about 3 months and if it is an average of mostly highs and all lows it could average out to a midpoint which could be very misleading in terms of control.
Although you can set your own parameters for TIR, the standard or Norm is 70-180. Imagine if half the time your blood reading was 70 and half the time it was 180, your TIR would be 100% but you wouldn’t be much better in terms of control.
For me I look at average blood glucose and standard deviation. I shoot for an average of 110 and a standard deviation of 20%. A standard deviation of 20% means you are in a narrow range above and below 110 which indicates good control.
Here is the link to the original publication that came up with that equation:
And here is the actual data that generated that equation:
While it is difficult to see in my attempt to copy the actual data, there is a LOT of scatter in the data that is used to determine the magic equation.
If you take your 1-3 month average of measured glucose and use the equation to predict your HbA1C, it may or may not come close to your A1C measurement.
What does A1c have to do with comparison to other people? My understanding is that A1c is the average percent of my red blood cells that have glucose-coated hemoglobin, and they generally circulate for up to 3 months, thus it’s my estimated average for the previous three month period. Where is that on a bell curve with other people’s blood? Unless you mean which A1c levels have been designated or categorized into one of the following: normal, pre-diabetic, diabetic. There needs to be some way to have those delineated. No?
Red blood cells be come glycated as they are released from your bone marrow. Depending on how much sugar you have in you blood at that time, they will be glycated at a predictable rate. Normally around 5 percent. As it increases then the glycation increases.
Once they are born, they don’t change no matter what your sugars are running but new are born every day.
Red cells are produced mostly at night so if you have higher sugars at night it will skew your results.
Also if you donate blood or have another reason for blood loss or if you are anemic, will skew your results.
Red cells live for 3 months which is why they say you have a 3 month history, but it’s really not so accurate.
Some people have a shorter life span for red cells.
Your best indicator is time in range. The GMI uses time in range in its calculation.
My a1c is always lower than the gmi predicts. My last a1c was 5.7 and my GMI said 6.0 when I got drawn.
I would only use both numbers as a rule of thumb rather than a definitive indicator.
Nothing is really ever a number in diabetes unless it is way out of range high or low. Diabetic control is all about trends and keeping the trends within the specific range you establish for yourself and are comfortable with.
