The HbA1c measures our blood in such a way that it gives a measure of how our average blood glucose has been over the previous month or so. The measurement you have been given is the new IFCC units, whereas you'll see a lot of us referring to our figures in the old units which were expressed as a percentage. I think, however, that you either misheard the figure of 20, or someone made a mistake, because that is almost unfeasably low I would think. A young, very healthy non-diabetic would have an HbA1c of about 27 minimum rising to about 37 max for an older non-diabetic. About the best (lowest) ever recorded on here for a diabetic is 30-31. I'd have thought that if your figure was 20, you'd be feeling exttremely ill. Low is good, but I'd have thought yours was impossibly low. Need to check I think.