I’m guessing the issue of glucometer accuracy has been addressed elsewhere (and if someone could direct me to a useful thread, that would be great), but I just thought I’d throw out my morning readings — literally and figuratively! — and see if anyone else has had such experiences.
Shortly after I got up this morning, my CGM (Medtronic) was reading 4.6 (83) with an arrow down. I tested with my meter (One Touch Ultra) and got a reading of 8.2 (148). My first thought was “*&%$ CGM!” Then (as in 5 seconds later) I decided to do a confirmation test on the meter: 11.4 (205). And another meter test, about 5 seconds after that: 13.3 (239). And yet another: 12.2 (220).
So now I’m very frustrated with both the CGM and my meter. Which reading do I use to determine my breakfast bolus? And what about the CGM (which is on day 4 of its life)? It’s now reading 3.7 (67) with an arrow down. It’s due for a calibration in about 15 minutes, so I’m guessing I’m going to get a big fat “CAL ERROR” message.
Grrrr.
P.S. As you’ve probably guessed, I’m using mmol/L for my readings, with mg/dL in parentheses.
After a couple more meter checks, I settled on an average of 12 (216) and decided to bolus for that.
Just calibrated the CGM with a 6 mmol/L spread between it and the meter. CGM isn’t going to like that, or that fact that my BG is now dropping from the bolus … terrible time to calibrate. What would you have done?
Thanks, John. I think I’ll follow your lead and get some strips for one of my (many) other meters. It’s comforting to know I’m not the only one being driven crazy. 
CGMS are having a variance of 15 percent( I recently learned this ) ; meters have a variance of 20 percent …one could hold of on " calibrating’ till numbers are more stable …suggestion : turn of sensor till numbers are better ???
On the side : when I have a BG test number higher than 11( x 18 ) , I wait till it comes down before I start my meal process …I correct with a needle shot , instead of the pump …comes down faster .
How did you make out Heather on the day you posted and there after ??
I use an Accuchek Aviva and find my numbers amazingly consistent. The strips are expensive if you don’t have insurance coverage, but if you do it might be worth it to get a more reliable meter.
I have a not-particularly-well-known-for-accuracy meter (Accuchek Compact) but under “optimal conditions” it is always within a few percent of the lab when I compare my meter’s bg at the time of the labwork, with the lab results. What I do is measure with the meter right before I go in to have my blood drawn, and measure again right after.
The suboptimal conditions I notice have little to do with the meter and more with how I get the drop of blood. Very cold weather and cold fingertips makes the meter readings go off. Wet fingertips make the meter readings go off (towards low side). Sticky fingertips make the meters readings go off (high side).