CGM inaccurracy

Okay so I wear a minimed metronic 754 with CGM system using enlite sensors.

I have noted the last few days where my sugars on CGM say I am 9.3 (167) so I give a correction. Then I test on my meter (which I should have done before the correction) and I am 5.2 (93) which I normally would NOT correct. This has happened a few times in the last couple days. It seems like my sensor is off but its only a few days old so I don’t really want to ditch it. Now I realize that I should test with the meter before correcting but honestly that is just annoying. Especially if I am correcting something that only marginally needing correction in the first place.

Any suggestions?

I will also say that I was always told not to calibrate if you are too high or too low. However, I have read on here that you shouldn’t calibrate if your meter number is too far from your sensor number, no matter what those numbers are. I can’t say I’ve done that specifically as I wasn’t aware this was the case so could I have messed up the calibration and if so how can I correct it? For this time and for future if it should happen again which it probably will at some point lol

I’d say my CGM and blood glucose are rarely the same. They should be closest first thing in the morning and 4 hours post-meals/exercise. The most annoying time is when I get low alarms repeatedly during the night and my meter check says 90-120. However, I have learned that it could mean that I will get a low within a few hours so I will eat a piece of fruit or some crackers anyway. As you said, it is always best to do a meter check before making any corrections. My doctor pointed out to me that I tend to be low most often during a day when I do a manual correct and don’t let my pump calculate the correction.
The Medtronic trainer I saw last January explained that 1 “bad” calibration (when blood glucose and CGM number are too far apart) can take up to 5 “good” calibrations to get better accuracy again. You can always disconnect the pump and sensor, give it a few minutes to an hour and then re-connect. That usually works for me. If not, they do recommend calling the help line. Believe it or not I am finding the Enlite sensors are much more accurate than the old Sof Serters.
I also find it helps to use tissue in an area with good circulation. The glucose has to get to and from the bloodstream and into that subcutaneous interstitial fluid so some areas work better than others. For instance, the backs of my upper arms are usually cold and I get very poor accuracy there, in contrast to my abdomen which has less fat and I guess better circulation.
My advice: Don’t give up on the CGM! It is such a useful tool for when you don’t feel a low and when you’re not sure what happened during a long period like overnight, etc. It also helps to support your A1c and show your endo where you need adjustments. I went from checking my BG 3 to 4 times daily to probably about 6 to 10 times. It all helps with understanding what your body is doing.

@MaggieJo - Makes perfect sense. I am no where near giving up on it - its saving my life and helping me prepare for pregnancy but its just a little frustrating. Especially when its beeping low low low or trying to suspend when I come to find out I am in range or even sightly nearing above range…I like the suspend automatically feature with CGM its just these situations that it can be hurtful not helpful. I will keep that in mind about not calibrating too far apart and trying disconnect and reconnect. Thanks!

Glad you are sticking with it! I don’t have enough patience to do the auto-suspend but I maybe when I am more comfortable with the accuracy or really worried about going dangerously low. I hear I might not need as much insulin when I get pregnant so I might need it for the transition.
Take care.

@MaggieJo fair enough…its mostly in the night that I like the auto suspend. Yes I hear first trimester less insulin, third trimester WAY more

I’ve been told it’s okay to calibrate as long as you don’t have any trend arrows showing. (I’m also using Enlite). When my sensor and meter aren’t matching up and I’m getting false alarms I usually silence the alarms for a few hours to give it a chance to catch up. It’s less annoying that way.

@KSmerk12 ya fair enough - it does take a few hours to catch up when its ‘lagging’

The only problem with calibrating when blood glucose and CGM reading are different is it leads to calibration errors and bad sensor alerts. Also, with the Enlite sensors the Medtronic trainer said it’s ok to calibrate when there is 1 trend arrow, never 2 arrows, but they don’t recommend it.

I have a MiniMed 522 pump but after hearing about the painful insertion and inaccuracy of the Medtronic CGMs, I chose to get a Dexcom 4G. It is very accurate, usually within 5 points up or down of my actual BS. However, after wearing the same sensor for around 15-20 days, sometimes it gets off up to 15-20 points. I paid privately for the Dexcom system (no thank you, Medicare!) and for the sensors, which are $80 each, so it is great to be able to wear them so long. Accuracy is essential and I was able to bring my A1C down from 9.1 to 7 in 6 months. I have lowered my range and plan to bring it down another .5 or more if possible. My goal is below 6.5.