hey there's a 15-20 minute delay with libre between the real state and the blood test one. It's not real time. You can add an alarm let's say below what is early low warnings. That can help push you to do a blood test. If you're going low or feeling funny, do a blood test. However libre should show what happened later on the graph. I've not had any bad sensors with readings but it's worth calling Abbot and asking if you get another event where the device didn't record it and your other normal blood one did.