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From New York, USA:

My daughter is now 17 and has given blood twice. Unless I'm mistaken, she is going to lose some of the hemoglobin upon which the A1C would be based (3 month intervals).

How will donating blood twice, 56 days apart, affect a hemoglobin A1C drawn every 90 days?


I'd need some more information, for example her weight, in order to roughly estimate blood volume, the timing of the two blood draws in relation to the A1c test and whether blood has been given more than twice in the last few months, etc., to come up with anything better than an approximation as to the effect on the A1c. This understood, the maximum change would be a few days after giving blood when the blood volume would be restored but not yet the normal cell content. Any reduction should be less than 10%; but this would not be easy to interpret because the 95% confidence limits of many of the glycohemoglobin assays are themselves +/- 10%. If you are concerned, it might be an idea to skip the A1c until an office visit that is some three months after the last blood donation and just use blood sugars to judge control.


Original posting 29 Sep 1998
Posted to A1c, Glycohemoglobin, HgbA1c


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