My Dexcom is accurate. I check it against a meter maybe once a week and they are within an acceptable range. I have it set to alert me at 70. I do tend to drop quickly for some reason. I just started with a new pump (770G) yesterday. I was thinking that perhaps my old pump was giving me too much insulin. I did check the totals though and they seemed to be accurate. Regardless, I moved to the new one and am still having the lows. I even reduced my basals when I put the figures into the new pump.