It gets a 1 because it is always 20-50 points off on my readings which defeats the purpose of it. I was trying to work with that fact but the alarm for critical lows keeps going off. If there was a way to adjust the # that causes it to go off then this would work for me. Also, the volume on the alarm is obnoxious. It goes off at 55 but my actual bloodsugar is 105 when I prick my finger and double check. So I'm in range technically but the sensor isn't reading it right. Think I might try Dexcom.