Weird results from pressure on sensor?

I have a Guardian sensor (my 3rd over the last 6 years). I love it.
For the first time, I put the sensor in my buttock - on the right side where I could reach. After 15 years of pumps and sensors, I’m running out of un-scarred real estate. It worked great, calibrated nicely, all good - until I went to bed. Then it claimed I crashed big time. CGM = 56, meter = 98.
Back to bed, sleeping on my stomach, calibration good, all great. Roll over - CGM = 48, meter = 102.
This has been going on for days (I leave my sensors in for 6-9 days). I’ve paid attention and even stayed awake monitoring it and sure enough, if I was on my side - putting pressure on the sensor, the transmitted readings dropped like a stone. If I was not, they would immediately go back up.The changes doen’t even look possible, huge jumps of 40 mg/dl (is that the right units) or more in 15 minutes, up or down. Sitting in chairs doesn’t affect it (just got back from a business trip, this didn’t even happen in an airplane seat).
My only hypothesis is that when I sleep on my back I’m pushing the sensor deeper into the tissue and the calibration is off?
I usually put the transmitter in my upper leg somewhere - including the outside where this effect should also have happened, but never has.
I like this “new” location, I can get to it, it is comfortable, it works during the day… But, it’s been keeping me up at night with constant erroneous readings.
Anybody have any thoughts?

Many people have observed the change in readouts when pressure is applied. I only know one way out of this: Attach the sensor to an area that you don’t sleep on.

I am not sure of the direction that your sensor is pointing, but when I insert mine back there, I make sure that they are pointing horizontal to the floor when I stand. If I have them pointing down or up (head to toe) it would move and cause these errors. A great place is the part of the back above the waistline but away from your backbone. That might be better for less pressure when you sleep.

Darn that makes my butt hurt!!!


rick phillips

When pressure is put on the sensor area the circulation of the fluid around the sensor is reduced and the sugar is absorbed by the surrounding tissue resulting in a lowing of the BG reading in the sensor. This happens anytime the sensor area is compressed and the movement of fluid in the interstitial area is reduced the BG reading will be lower.

Some of the sensor manufactures have suggested that this may be solved with something like a hemorrhoid donut pillow, taking pressure off the tissue around the sensor. This is one of those CGM things that they don’t tell you about.

I have test it and they are right, no pressure good readings, pressure = low bg readings.

S. W : Are you referring to all brands? TS : I need to check this out with my MM …
I hate it , when I have to state : never too old to learn …I probably don’t mean it at age of almost 70 .
Thanks for posting TS :slight_smile:

thanks everyone. I’ve been using the sensors for a long time, so I’m surprised this has just been an issue now. I’ll try inserting the next one 90deg off to see if that helps. I like the butt as a place otherwise, it’s oddly more comfortable. I’m not sure why I never tried it before, except for the reach factor, have to put the tape on blind and hope I cover the sensor.

Ts …Do you pull the skin " taught " , as in opposite to giving a shot by needle, when I pull the skin up ? I’ll try my butt too , next time …esp since I do the bad thing: love sleeping on my belly.

I don’t do either, I just do - LOL. But, I’m decidedly overweight but very active, so I have an odd fat/muscled body composition. I’m trying the other cheek this week, and so far so good.

This is true with all sensors because they rely on interstitial fluid glucose to measure the glucose, when the fluid is not getting glucose from the surrounding blood, the glucose measurement will drop while the glucose in the blood rises. If the discrepancy is too great the accuracy for the CGM measurement will be out of calibration with the glucose in the blood and glucose in the rest of the body.

Absolutely! I have experienced this with pressure all the time—particularly toward the end of a sensor’s life. Or if I don’t get an ideal spot.

Just tonight after recharging my transmitter after 7 days and reconnecting this afternoon, it started doing this (I’m most often not lucky getting my sensors to last more than 7 days).

If I was sitting, I would get accurate readings. (My chest tends to rest on it…lol).
But when I walk around, the reading drops dramatically.
Then rises when I start sitting again! (Will rise if I press my hand over it as well)

Then the signal just dropped completely an hour ago or so. Like I said, the pressure issue with me, is a sign the sensor isn’t going to last. :frowning:

EDIT: Just read more closely, and seems I have opposite results. Pressure–normal reading, low pressure–low readings. Weird.

@ Jaclyn,
I’m not sure that’s weird as you say - it’s how it is when you calibrate it. If you calibrate it sitting, then the readings should be right. As for going low without pressure, probably the mechanism is more complicated. It also could be the “old” sensor issue more than the pressure, or activity moving the sensor a little.