how accurate is Hba1c test?

I was told that there is no point in doing the Hb1Ac at intervals any less that 12wks as it takes about that time for all the blood cells to be renewed by your body and the test will only indicate an average for that period.

the_anticarb said:

Also does anyone know what could skew the results eg if someone was (hypothetically) to run their blood sugars really high in the week before the test would this skew the result to a higher reading even though it is supposed to be the average over a ten week period.

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Yes it does effect the a1c result as it's nearly half of the 9-10 week period that the result measures. When I was first diagnosed my consultant said that he knew some diabetics would keep tight control weeks before their hba1c was due so that they got a lower reading, after this time they would revert back to their previous bad habits of eating what they like and not monitoring, so this would apply the other way round.

Personally, I find my day-to-day control as a more accurate measurement of my overall control, and believe my 7,14,30 and 90 day average readings on my meter a more accurate portrayal, even though as you say they can be +/- 10 variant.

Nigel

HbA1c indicates average blood glucose over the previous 120 days. It's a little more complicated than that because your more recent BG levels affect the A1c more than that from 2-3 months ago. For a given A1c value the contribution of the blood glucose is:

1-6 days very low
7-30 days 50%
31-60 days 25%
61-90 days 15%
91-120 days 10%