I have a fairly rare genetic condition that leads to consistently high hematocrit levels — in excess of 50 pct. When I was first diagnosed with Type 2 four months ago I was given a OneTouch Ultra2 BGMS. At first I was pleased at how easy it seemed to keep my measurements below 140 mg/dl, but soon became suspicious. Sure enough, I found that the spec upper limit of hematocrit for this BGMS is 50 pct and that at high levels it underreads BG. Not good!
Some review of the device literature showed that one inexpensive and available BGMS that is not very sensitive to hematocrit is the Bayer Contour Next. I got one and in cosampled comparisons found that its readings were an average of 21 pct higher than those of the Ultra2! I've now gotten an A1C and found that its results correlate well with the Contour Next readings.
Odds are that you don't have hematocrit levels nearly as high as mine, but if by any chance you do it's a very good idea to check whether your BGMS is affected by them and if so change to a system that isn't.