Hi chri5, you say your reading was 8 before eating. Bg meters work by giving an indication of your current bg levels but are not 100% accurate in fact they work to within a + or - 20% so if you had a reading of 8 mmol/L it could theoretically be anywhere from 6.4 and 9.6 and even taking two tests back to back using the same blood sample you are unlikely to get the same reading.
There could also be 100 other factors involved here from you having a slight temperature to you having a hot or cold bath/shower, lots of things can affect your readings. So dont worry about an odd reading here and there, they are to be expected as home meters only give an indication of your curent bg levels. You only really need to be concerned with an overall pattern over several weeks or months which is why an HbA1c test is so important as it gives an accurate reading over the last 3 months (ish).
http://en.wikipedia.org/wiki/Glucose_meter