Why am I getting a twenty-point higher reading with my blood sugar with my left middle finger than my right finger?

Consistently? If this happens once in awhile and the testing from each side is around the same time, make sure both hands are clean and completely dry. Glucometer reproducibility may be a problem also, though maybe more likely with high rather than normal blood sugars. If you check blood sugar from same finger twice, sequentially, will there also be a difference?