I have found when I am anxious or have had a bad nights sleep my glucose readings go up. I have had them retested several times in the last few years whilst in Peri. I tend to go to the GP when I am at the end of my tether with worry about something, they do the blood test. Glucose is borderline. I go back two weeks later after better sleep and hormones not as crazy, reads normal. I guess getting a consistent reading over time is key.