Dexcom verse a1c

Hello. Curious if anyone else has a big discrepancy on the Dexcom G6 a1c reading verse the Endo’s actual a1c reading during your visit. Dexcom shows my daughter’s a1c at 7.4 but Endo appt says 5.6. I’m not complaining, verym happy either way just wondering about the wide range. Anyone else experience this? BTW, love the Dexcom.

@Maryjo.marshall HI Mary Jo,

“it depends”. the answer in this is buried in math so please excuse my explanation.

If DEX is giving you a simple average of all readings, or a time weighted average, or an integration of blood sugar over time, for the duration of a blood cell lifespan. Then the HbA1c and the DEX “average” may be significantly different.

also, you have to look at the blood test data to determine what their test range of normal is: example - my friends at Labcorp have their HbA1c normal span at 4.5% to 5.5%, which means that when THEY test my A1c, the number will be lower than, say if their range was 5.0% to 6.0%.

can I ask: who the heck cares? , That a1c is awesome if she isn’t getting lows! Keep up the fantastic work. also, I hate A1c as a report card… even when mine are near perfect it still makes me angry., but that may be just the old man in me.

Is this a BG average or SG average on the Dexcom? It could also be calibrating incorrectly.

me again @Maryjo.marshall, I can’t find anything on the G6 calculating a1c… in fact, I found written materials from Dex, that clearly says the G6 (G5 and G4 all) does NOT calculate a1c - so I am now confused (which happens a lot). do you have the Dex set for mmol/l? did you backwards calculate a1c from a 120 day average? I suppose it doesn’t matter all that much.

anyway, I found a page on diatribe that is informative (if you have time and want to learn more): https://diatribe.org/understanding-average-glucose-standard-deviation-cv-and-blood-sugar-variability

Hi. Thank you all for your help with my question. I was just looking at the Dexcom G6 summary reports. It will give an average blood glucose over 90 days and then will calculate what that a1c will be. My daughter is around 170 average per Dexcom equating to 7.4 a1c. But when we go to the Endo she was at 5.9 for an entire year then dropped to 5.6. I thought from the Dexcom numbers her a1c would have increased over the past few months. Overall I am happy with her management. She does a pretty good job. Thank you again.

On my Medtronic device, Average Blood Glucose (BG) is the average of glucose readings entered by the user from their handheld Glucose Monitor. Maybe 2 to 3 readings per day for sensor calibration.

Average Sensor Glucose (SG), is the average of glucose readings measured by the Constant Glucose Monitor. One measurement every 5 minutes, or 288 measurements a day.

SG is accurate for predicting A1C, BG is very inaccurate.

Mary Jo @Maryjo.marshall, like any lab test, the HbA1c can be “off” for a given person and there is not always an explanation. I’ve compared my lab A1c results for the comparable 90 day periods calculated by Dexcom Clarity and found that one was off by 0.01 and the other by 0.02 - both lab tests were lower. On a daily basis, I look at the Dexcom ESTIMATED A1c and the calculated average BGL and note that they do not fit in with my table of comparison values; Dexcom always reports a higher A1c.

As I recall during the development of the HB/GA1c - in which I was a participant in the 1970’s, A1c is calculated [guessed at] by measuring the proteins which stick to the globules of blood. It could be that the coating in your daughter’s blood is thinner [?].
Another thought - do you compare her G6 readings with readings from a meter; and how accurate is the meter? Something I do, is compare my CGM, a G5, reading with the lab report - the lab report has the time the sample was collected.

@Joe, added to the Clarity report a month or two ago was a feature called “Glucose Management Indicator” which is the Dexcom “guess” at what an HbA1c may be.