Question about A1C

[NicHolzhauer]

How long of a period does the A1C test measure. I have heard 2 to 3 months. I was diagnosed on 3.17.09 and I see the Endo on 6.18.09. Will my results show data from the first few days where my numbers were still on the high side?

[NicHolzhauer]

Also:

According to Wikipedia a 7.0% A1c is 150 mg/dL, but according to a different one, a 7.0% A1c is 170 mg/dl. Which is right?

[TedEMTP]

I was recently diagnosed and my doctor said the A1C measures your average blood sugar for the last three months.

She also said the breakdown is that 25% of the A1C is made up of your BS three months ago, 25% is made up of your BS two months ago, and 50% of the result comes from your average BS for the last month.

[CountYourselfIn]

I keep reading that it takes 5 weeks for any sorta dietary/treatment changes to affect your A1C.

Don't know what fraction of your overall test could hypothetically be effected by 5 weeks, but apparently that's the time to make a significant change.

You should ask your doc about it - why every 3 months/how much time is represented by the test.

Maybe someone reading this who's got an appt this week could ask?

[BlueSky]

At one stage, I tested every month and I was able to see the difference. See 2004 in the graph below.

http://i288.photobucket.com/albums/ll181/stratplan/hba1c0508.jpg

[NicHolzhauer]

I'm a little bit confused. Does this mean my A1c will be higher then it should be? My meter says my average is 118 in the last 90 days, shouldn't the A1c be about that?

[BlueSky]

An average of 118 corresponds to an HBA1c of 5.5%. But if your numbers have been coming down over the last three months, the actual HBA1c would be lower than this because the last month's numbers are more heavily represented than the previous 2 months'. On the other hand, your tests may have missed lot of highs, like after meals, which would mean that the machine average is understated. This will have the opposite effect on the average. It will be interesting to see what the actual result is. :)

[sumi]

Hi Nic,
I believe Ted's answer is correct. Depending on how often and when you test, your A1C may or may not match up perfectly. Mine did. There is some individual difference in how quickly your body renews these cells. ( Apparently anemic people have a lower A1C). Since the measurement is weighted to the most recent time, you should have a great A1C.To the right of your screen under site navigation is the heading converters. It worked for my calculation, and according to it, an A1C of 7 = average bg of 172.

[alexalisbeth]

The converter in the sidebar gives the same number as this does: Convert Glycosylated Hemoglobin A1c to Average Blood Sugar Level (http://www.obfocus.com/calculators/HemoglobinA1C.htm) except this has a tiny bit more explanation on the actual numbers used... It gives this as a reference: Defining the relationship between plasma glucose a...[Diabetes Care. 2002] - PubMed Result (http://www.ncbi.nlm.nih.gov/pubmed/11815495?dopt=Abstract)

This is the exact conversion my Endo was giving me, and I like to think he's a smart guy. (now the Medical Director at my med center, which is not a small clinic...)

[NicHolzhauer]

Thanks a lot for the replies.

Well I was diagnosed at 440 something, and the first couple of tests I did after diagnosis were in the upper to mid 200's, so those increase my average even more.

Yes, I know that there are postmeal highs, but also long periods of good nighttime numbers. I hope it is under 6... gotta love the Honeymoon Phase (although I have done a lot of work toward this...including lots of excersize and changed/reportioned what I have been eating. When I go there in a few weeks I will report my results...and also my A1c from diagnosis.

All this time I was looking on Wikipedia thinking an A1c of 7 coresponded to a BG of 150... whoo hoo! That means my results will be even better.

[NicHolzhauer]

Alex, I noticed clicking in your first link, there is a number for Average Plasma Blood Glucose and another number for Average White Blood Glucose. I noticed the difference that I have been seeing - some sites use the Plasma and others use the White. Which is correct?

[alexalisbeth]

Alex, I noticed clicking in your first link, there is a number for Average Plasma Blood Glucose and another number for Average White Blood Glucose. I noticed the difference that I have been seeing - some sites use the Plasma and others use the White. Which is correct?

The plasma (higher) is the number that my Endo gives me. I imagine they're both correct, but as far as which one is more "standard" I really don't know. I bet Lifescan et al have something in their fine print about which they measure... I'll look for it.

[Real4]

Also:

According to Wikipedia a 7.0% A1c is 150 mg/dL, but according to a different one, a 7.0% A1c is 170 mg/dl. Which is right?

I suspect that no one really knows. If you think of what would be required to actually test this, you perhaps can understand why. This is not a logical or mathematically relationship, but a physical one between two complicated biological functions.

You would need a very large sample of people who had their BG levels constantly monitored for months (with a CGMS) to get exact numbers.

[Real4]

She also said the breakdown is that 25% of the A1C is made up of your BS three months ago, 25% is made up of your BS two months ago, and 50% of the result comes from your average BS for the last month.

This is only approximately accurate. The main determinate for the three months is the life span of a red blood cell. In general, very general, red blood cells survive for three months. But some cells die off quickly and some last very long; and for different people of different ages, genders, state of health, etc., etc. the spectrum of the age distribution of cells will be different.

Rather than try and be too exact, it is more useful to think of an A1C as an average for about three months very much weighted towards the most recent period.

[alexalisbeth]

I looked around and it appears that home meters (A1c, fingersticks, etc) use whole blood to measure glucose, but labs use only plasma. So when my doctor says my A1c is 7.1% and that means an avg BG of 175, I would actually see an avg of 157 from my meter (if I were accurately able to catch the whole picture on my meter...)

So basically, if you are seeing lower numbers on your meter at home than your doctor tells you your avg BG is, you're likely not doing that much worse than you thought you were...

[RubyRed]

Nick, I am new to this site and can not figure how to make my first post and introduce myself to the group. Where do I go for help? Or can you walk me thru this step. I think the A1C is an average measure of your blood sugar over the past three months. Thanks for any help. RubyRed

[sumi]

Hi Ruby,
To the right of your screen, under diabetesforums.com, you will see Forums listed second. Click on it and introduce yourself in.... wait for it.....Introductions!! Yes, I am a bit of a smartypants, but as you may find out, also rather technically challenged.