CGMS way off?

[KitKat]

For you CGMS users I have a question.....DS CGMS says 175....finger BG says 275. This has been happening more often than not. Why is it doing this? Is there something wrong with the sensor? Site? I thought I would try here before calling the helpline because most of the time you guys have more experience.

Thanks in advance!

[WestinsMom]

Try calibrating at higher numbers a few times. I have read a lot lately about giving it bigger ranges.

[vettechmomof2]

Which cgms is it?

Also, we will have some problems if we are having quick fluctuations of blood changes. Now to help(at least with the Dexcom) if we are having an off moment we just calibrate again.I do not know if that is possible with the minimed though so cannot help there.
We also found that if we were having those fluctuations we changed our basals around to counteract those number changes and no more problems.

GOod luck,
Allene

[thebestnest5]

That happens to us once in a while and sometimes the sensor finally corrects itself and other times I just have to pull it. I dislike sensors like that.

[KitKat]

We are using the RT Minimed 722 CGMS. I hope we don't have to pull the sensor but I guess this will give me a chance to try it in his arm. He is not thrilled about the idea and I am a little nervous too. He doesn't have much fat and he is rather muscular.

[Mary Lou]

I don't think that's all that unusual. Was this a period of rapid change? the sensor lags about 15 minutes behind the finger stick, and really struggles to catch up with BG is on the move.

I also think that the margin of error is more pronounced when BG is very high, but I would've expected the sensor to be closer than it was.

Keep calibrating when stable. Sometimes the sensor will line back up and sometimes it is just a 'bad sensor". i wouldn't pull it unless it was way off for an entire day. I hate tossing those things!!

[TripleThreat]

i find it happens when there is a drop at innitial calibration start up

to counter act this i take the number and increase it by 1 unit, so if reading was 6.6 (118.8) i say it was 7.6 (136.8) then we usually get a sensor that is spot on at next calibration

you will also get bad readings if you calibrate every time you do a reading.

[Kaylee's Mommy]

if the numbers are changing rapidly in either direction the sensor will lag but will catch up when the numbers settle down.. if I calibrate during a low then it will ride low (I can still see trends but the number won't be close) I try and calibrate when its in the mid to upper 100s and then its typically right on.. I use to calibrate no matter what when it would ask for it.. but now I've learned that if I just let it go (I hate missing data!) and miss a half hour or so, and wait to her bg's are steady then I have a good cal. which will make the sensor more accurate.. so I'd rather wait and cal at a good time, missing a 1/2-1 hour worth of data rather than not waiting and screwing up a cal, getting crappy data for the rest of the day.. took me a while to get into this mode of skipping a cal if her bgs weren't steady though.. also, for us, when I sensor is dying, it can't keep up.. it'll say Kaylee is hypo all day when she's not..

[Twinklet]

Others have much more experience and can answer the question better than I can, but I just wanted to say I definitely see a 15 minute lag with rapidly-changing numbers. Otherwise the sensor is usually exactly right for us, within a few points. I've never seen a 100 point difference, ever--I wonder if that is a bad sensor?

[Ginger9909]

The first time we did the sensor i also got ranges of 100 off. Its pretty frustrating, especially in the middle of the night being woken up constantly when her BS is actually 250 and the CGM says 350. i havent been in a rush to try it a second time.

[Darryl]

For you CGMS users I have a question.....DS CGMS says 175....finger BG says 275. This has been happening more often than not. Why is it doing this? Is there something wrong with the sensor? Site? I thought I would try here before calling the helpline because most of the time you guys have more experience.

Thanks in advance!

We've been using the Guardian for about a year. It is very accurate most of the time, but you can expect that any time it shows a high BG, the actual BG could be even higher. It's not uncommon to see the BG read 200, and it is really 280.

What's most important is to recognize is that when CGM is telling you that the BG is high, it is not crying wolf. When the sensor reads 175 and it's not right after a meal, do a blood check. Whether the actual BG is 175 or 280, the sensor has done it's job.

From there, give the correction appropriate from the actual blood check (not the sensor reading), and do NOT recalibrate the sensor. Once the BG gets back under 150, the sesor usually becomes accurate again. If you calibrate from a high BG reading (where the sensor is at its biological "celiing"), you may actually make it much less accurate in the target range.

[KitKat]

They told us to recalibrate at least 2 times a day. I checked and my DS is updating the sensor at least 4 times a day. Could this be the problem. I think he is calibrating at a high number. Today it alarmed and said he was high. (Our alarm goes off at 250) Finger BG was 489!!!! This is crazy and I am wondering...should I lower the alarm for the high number? Do you think we should do 180?

[Lizzy731]

For you CGMS users I have a question.....DS CGMS says 175....finger BG says 275. This has been happening more often than not. Why is it doing this? Is there something wrong with the sensor? Site? I thought I would try here before calling the helpline because most of the time you guys have more experience.

Thanks in advance!


Well...we are new at the cgm so I am by no means an expert but I'll give it a try!

I have found that when Bethany's finger stick does not match the sensor is when she is actively dropping or increasing. For instance, the sensor says 110 but her BG is 160. I look at the history and it says she has been going up about 4-6 points every 5 minutes steadily. Then all of a sudden, an arrow up will appear.

I know some people have said that this sort of discrepancy is normal but IMO, I don't think so. I think the sensor being off by 100 pretty often is significant. I have read that the angle of insertion and allowing the sensor to "wet" thoroughly prior to connecting the transmitter is the key. I allow at least 10-15 minutes before connecting the transmitter and I insert (in the buttocks only so far) at an angle larger than the 45 degree angle on the insertion device. Usually 60 to 80 degrees. The sensor and BG values are rarely off by more than 10 points unless she is actively rising or lowering.

Hope this helps!

One more thing, I callibrate 3 times a day. Usually not more or less than this. I never calibrate when directional arrows appear or even if her history says she has been going up or down more than 2 points every 5 minutes steadily. I will usally wait for a more stable time to calibrate even if it means missing data.

[krstn9@yahoo.com]

The times I have seen the cgms way off as you speak is when my son is rising so fast that the cgm has not caught. This seems to be the major reason. The other times this has happened is when we are 7 plus days and the sensor needs to be pulled. As you probably know, when the numbers get higher, there is a bigger variance in the numbers between finger and cgm. If none of these fit the situation, than I would wait until you get a time where you have a somewhat even bs time and calibrate and try again. If it doesnt work, pull it. I do believe that working with the CGM is easier as time goes by and you have more experience underneath your belt (not that you don't :) ). Not to say that sometimes you get thrown a situation that just doesn't fit the mold and you have to try again. Good luck.