New A1c/ Average Blood Glucose calculator

I was trying to use the new formula that links A1c to average blood glucose and could not find an online calculator so I wrote one myself. It will also convert mmol/L to mg/dl and back again using the truly accurate 18.05 conversion factor.

The new ADAG formula yields different blood sugar equivalents than did the older DCCT formula most of us are familiar with. Becuase it was derived from CGMS observations, it is supposed to be more accurate.

Here’s the calculator:

Jenny, I have one question. You calculate it via a new formula but I believe every lab has its own way of testing A1c.
My final lab test was showing 5.7%. And according to my lab this was the upper level for normal values. Also I was doing a lot of finger pricking like 10 per day. I know that my BG has never been over 110 for the last 2 months.
But when I used your calculator 5.7% converts to 117mg/dl. I believe either there is a problem with lab’s way of testing or maybe my BG values prior to 2 months was higher. Who knows?

There has been a standard for A1c testing that many labs in the U.S. have been using. But recently a new standard was proposed which if it is adopted should solve the problem you cite.

Here’s an article about the old and new A1c standards.

My own meter readings never match ANY of the formulae. I have blogged about why this is and you can read it here:

More Insight into why A1c doesn’t match your meter.

The important thing is that most of us are consistently higher or lower than the average. It is not known however whether the complication profile matches the meter or the actual blood sugars as tested.

My A1C seems to match my average post-meal number, not my overall average. My last one was 6.1, which translates to 129, yet my fasting number was around 95. I would hit 130 at about one hour post meal, and be back to under 100 at two hours. Makes no sense at all. I test up to 12 times a day, even checking in the middle of the night occasionally, and was never much over 130 after meals and under 100 over night and in between meals. When I was first diagnosed, my A1C was 7.2 (160) and again, that was my average only during the two hours after meals and my fasting was in the 90s. My numbers were so low that the first endo I saw refused to believe I was even pre-diabetic. I read somewhere that A1Cs can vary up to a point over or under depending on the individual (with the same BG numbers.) I am convinced my A1C is about a point higher than my average. My endo was unable to give me any help on why this happens, or to tell me if I should be concerned about a higher A1C when my BG numbers are so low.

mine was spot on with 129 for a 6.1!

Thanks for the explanation.


My A1c also seems to match the majority of my post-meal peaks, too. It’s supposed to map to 117 which is about where I am post-meal. I’ve been keeping my fasting bg mostly in the 90s and probably go over 140 once every 2 or 3 days, but only briefly.

The lowest A1c I ever attained was a 5.2% and that was while eating an extremely low carb diet. I couldn’t duplicate it ever again, even on the identical diet, and I ended up at 6.2% still eating low carb at one point.