Id try different spots but it'd turn into an expensive hobby! I alternate arms and wear it on the outside for convenience. When worn on the left arm it has the added bonus my wife can scan me whilst I'm driving. Trouble is I'm clumsy, always have been, runs in the family, I'm forever knocking it on door frames and stuff. I've had a couple of premature failures, when I've removed the sensor the little pin is bent! Wonder if it's my clumsiness? I know some people wear them on inside of the arm, does it irritate? Or the back, awkward to scan. Where do you find best?