We can't post links, but when Ruth mentioned a chart she had on what your average BS reading was based on the HbA1c measurement, I went looking and found this formula to use so you can calculate it for your own specific reading:

Mean Blood Glucose (MBG) was determined using HPLC and the Nathan Formula:

HbA1c % X 33.3 – 86 = MBG mg/dl.

Example: Your HbA1c reading is 7.0 %, so (7)(33.3) - 86 = 147 mg/dl average.

wb

WB -
That's interesting. Where did you find the formula? According to the chart I have, your formula is off a bit; however, it's possible that the chart I found isn't accurate. It's so darned frustrating trying to get valid information over the internet (or even from our own doctors) sometimes. I'm going to post the chart I got (which, stupidly, I trimmed to fit on my bulletin board so I don't know where it was from). Maybe we can both do some more research and come up with something we can feel confident with?

A1C of 4 equals average bg of 65 mg/dl (or 3.5 mmol/l)
A1c of 5 equals average bg of 100 (or 5.5)
A1c of 6 equals average bg of 135 (or 7.5)
A1c of 7 equals average bg of 170 (or 9.5)
A1c of 8 equals average bg of 205 (or 11.5)
A1c of 9 equals average bg of 240 (or 13.5)
A1c of 10 equals average bg of 275 (or 15.5)
A1c of 11 equals average bg of 310 (or 17.5)
A1c of 12 equals average bg of 345 (or 19.5)

(For those who are curious, the figure in parentheses represents mmol/l, which is the metric equivalent to our mml/dl. The U.S. uses mml/dl, while the rest of the world is on the metric system and uses mmol/l)

Ruth

Ruth -

I can't give the website, but "Mean Blood Glucose (MBG) was determined using HPLC and the Nathan Formula:" is a copy/paste from it.

wb

Ruth -

Check out this Healthboards link:

http://www.healthboards.com/boards/showthread.php?t=174017

I found the "Nathan Formula" on 5 websites, but the above link makes reference to:

Avg. BS = HbA1c % x 35.6 - 77.3 from a link given in the thread referenced above. Your chart numbers seem to be closer to this forumla than the Nathan formula. I've done a spreadsheet so I can compare all 3. Here it is for us number junkies :D

HbA1c (HbA1c)(33.3)-86 (HbA1c)(35.6)-77.3 Ruth's Chart
5.0 ------------ 80.5 ------------ 100.7 ------------ 100
5.5 ------------ 97.2 ------------ 118.5
5.6 ------------ 100.5 ------------ 122.1
5.7 ------------ 103.8 ------------ 125.6
5.8 ------------ 107.1 ------------ 129.2
5.9 ------------ 110.5 ------------ 132.7
6.0 ------------ 113.8 ------------ 136.3 ------------ 135
6.1 ------------ 117.1 ------------ 139.9
6.2 ------------ 120.5 ------------ 143.4
6.3 ------------ 123.8 ------------ 147.0
6.4 ------------ 127.1 ------------ 150.5
6.5 ------------ 130.5 ------------ 154.1
6.6 ------------ 133.8 ------------ 157.7
6.7 ------------ 137.1 ------------ 161.2
6.8 ------------ 140.4 ------------ 164.8
6.9 ------------ 143.8 ------------ 168.3
7.0 ------------ 147.1 ------------ 171.9 ------------ 170
7.1 ------------ 150.4 ------------ 175.5
7.2 ------------ 153.8 ------------ 179.0
7.3 ------------ 157.1 ------------ 182.6
7.4 ------------ 160.4 ------------ 186.1
7.5 ------------ 163.8 ------------ 189.7
7.6 ------------ 167.1 ------------ 193.3
7.7 ------------ 170.4 ------------ 196.8
7.8 ------------ 173.7 ------------ 200.4
7.9 ------------ 177.1 ------------ 203.9
8.0 ------------ 180.4 ------------ 207.5 ------------ 205
8.5 ------------ 197.1 ------------ 225.3
9.0 ------------ 213.7 ------------ 243.1 ------------ 240
9.5 ------------ 230.4 ------------ 260.9
10.0 ------------ 247.0 ------------ 278.7 ------------ 275

Ruth -

I found your numbers. I may be skirting the edge of posting here, but they come from a paper entitled, Defining the Relationship Between Plasma Glucose and HbA1c Analysis of glucose profiles and HbA1c in the Diabetes Control and Complications Trial by CURT L. ROHLFING, BES; HSIAO-MEI WIEDMEYER, MS; RANDIE R. LITTLE, PHD; JACK D. ENGLAND; ALETHEA TENNILL, MS; and DAVID E. GOLDSTEIN, MD.

They took a lot of samples and did a linear regress to get the 35.6*HbA1c-77.3 formula, and cited your numbers as a lab approximation in a table in the paper.

Mystery, solved, I hope. :)

wb

Wow, WB, I'm impressed! A lot of research in a very short time. Thank you!

I guess the final answer is...it's all approximate, but any of these guidelines will suffice to keep a person abreast of what their blood glucose is doing on a daily basis.

One thing I find (this is just myself...others may have different reactions) is that when I convert my A1c to average bg, it usually gives me a swift kick in the pants and motivates me to do better. For this reason, I like having a conversion chart (or formula...thank you, wb) on hand.

Ruth

WB's numbers look like what Unilab/Quest is using. They had 127 for 6.4 A1c and 97 for 5.5 A1c.

A little more research showed me that DM Nathan's original formula appeared in the New England Journal of Medicine in 1984.

wb