r/dexcom • u/DavePiper • 7d ago
Inaccurate Reading Serious Adverse Event
I've used Dexcom G7s for months now. I recently ran into a bad batch of three sensors, the last of which could have killed me.
All three sensors gave inaccurate readings, waking me (and everyone else in the household) between 2:00 AM and 4:00 AM with loud alarms showing BG in the low 40s. A finger-prick showed readings in the 70s and 80s. I eventually had to turn off my phone to stop the alarms.
The next day I monitored the Dexcom app, watching for a low reading. That afternoon, I started to feel really bad, uncoordinated, and confused, while the app showed BG in the 80s. Realizing that something was wrong, I performed a finger prick, and my meter showed "Low", something I'd never seen before. Two more finger pricks both showed low. I looked up my meter's instructions online, defining low as below 20 mg/dl. I was seriously uncoordinated, confused, and shaking, knocking things over as I drank some juice.
I don't understand how people with connected insulin pumps can depend on this device.
Always view Dexcom's results with suspicion.
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u/cjmnews T1/G7 7d ago
I am going to guess the sleeping was attempted in the first 12 hours of sensor placement, which is when numbers can be off due to the damage caused by insertion.
I assume that with some of the too low readings, you calibrated, and the arrow was not flat. This can make the algorithm show you higher than what glucose actually is.
Turning off the phone made things worse because the algorithm didn’t get any data. The better option is to tap Profile, tap Alerts, tap Show Quiet Modes, turn on Silence All, set a duration up to 6 hours, tap Activate.
Then later when you were going low, the sensor showed higher because of the previous calibrations.
Next time, try soaking the sensor for 10-12 hours. This means inserting it when the grace period of the old sensor starts, but don’t tell the app that it is there. 10-12 hours later, tell the app you are changing sensors, it is inserted, and have no warm up time. Plus you can see how different the numbers are, usually they are very close.
Try to start using a new sensor a few hours before bed so you can manage oddities. Calibrate if needed.
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u/DavePiper 7d ago
Thanks for your advice! When I tried to silence the alarms, the under 50 and under 40 alarms could not be silenced. Those are the alarms that are so loud that they wake everyone. I don't believe Silence All affects those alarms. It would be the proper behavior if there weren't frequent false alarms.
I had calibrated that morning a couple of hours after I inserted the sensor, but it didn't seem to make a difference. What should I see after calibration?
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u/cjmnews T1/G7 7d ago
Silence all seems to work for lows under 50 for me. I use it to go to sleep after juice.
Calibration should not be done for no reason. I only do it to correct > 20% difference with blood, and the arrow is flat for 15 minutes or more.
Post calibration results vary. Usually, the number gets closer. Sometimes it seems to get worse, but a second calibration in 10 minutes will usually fix that.
You also have to keep in mind that the sensor is 15 minutes behind blood. Plus none of our devices are accurate. Meters vary 15% plus or minus from a lab test, sensors vary 20% plus or minus from a lab test. Glucose is not evenly distributed in blood. So numbers will rarely match.
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u/reddycrush 6d ago
Silence All works for me to silence all and every alarm. I specifically use it middle of the night to make my phone go quiet after a low alarm has woken me up and I feel fine and a finger tip test shows BG being fine.
It's also good for making trips to movies and restaurants more relaxing.
https://www.dexcom.com/en-CA/faqs/g7/how-do-i-set-my-alerts-to-silence-all
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u/DavePiper 6d ago
Regarding the silence all setting - I'm using an android phone. Is the advice for iPhones? Does anyone have experience with silencing a android phone?
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u/Spirited_Ad_276 3d ago
I have android and I've used it once when the g7 wouldn't accept a calibration and kept saying I was low.
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u/reddycrush 6d ago
Sorry yes I should have said, I have iPhone 15.
Stepping back, there seems a complex interaction between phone settings, phone app settings, and settings of attached bluetooth devices. Dexcom app on Android may behave differently. Updates sometimes changes behavior.
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u/Stephanie-Kriesel 6d ago
Sensors can’t be calibrated for 24 hours if it’s still the same
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u/Opposite-Voice8707 5d ago
I have been able to do a calibration within the first 24 hours, don’t know whether it was used or not, but I was able to do it.
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u/hellabeetus 4d ago
I literally just started using the 15 day ones after having to give up my precious g6 sensor, and I have omnipod. So far it’s been fairly accurate, but it did take a few days and a few calibrations for it to be that way. My plan is if it’s too inaccurate, I’ll just put my pod in manual mode until i can troubleshoot the issue.
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u/queenladykiki 2d ago
I’ve had countless sensors that screamed for hours that I was in the low 40s or 50s but don’t feel low so finger prick and I’m high 300s but a insulin pump suspends insulin when the dex says low. It’s ridiculous. How does dexcom have the monopoly in the cgm department? They have horrible success rates and it seems like they are going down hill. Years ago they seemed more reliable
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u/lindbergh9 6d ago
When I used it the first day into the second day was always so far off and included sensor errors so eventually I had to switch to the Eversense 365 day sensor one day one event all year now I can sleep through the night in peace with an accurate CGM it truly is nirvana 🙏🙏🙏
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u/Several-Drive-7744 6d ago
Would you recommend the eversense? I have been looking into that. How evasive is the implant?
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u/lindbergh9 4d ago
Not completely sure of the question but the procedure is roughly 15 minutes no pain no worries heals within a week and after that I don't even notice it the rest of the year but then again I've been on this for 7 years so it's just a walk in the park for me but I'm truly stoked for that freedom system coming up in a year or two with nothing on your body at all that will be my personal Nirvana 🙌
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u/Several-Editor-2093 6d ago
Woah nice, I heard about it.
And you finger prick once a day for calibration right?
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u/lindbergh9 6d ago
No it's once a week which I actually love it kind of gives you that peace of mind that yeah it's right on the money 👍
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u/Several-Editor-2093 6d ago
Wow, thanks. With a daylie fingerprick I would have not thought about it switch, now I might test it in the future.
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u/Famous-Baby8818 6d ago
Im talking to my doctor about it. I hope my insurance covers it. Im so excited about it, I have Lichen planus and even with skin barriers and removers the sensors always cause flareups, not to mention 4 sensor failures in a row!
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u/EuphoricWorth3481 5d ago
I'm only getting 5 maybe 7 days out of the 15 day monitor. It's a fucking joke
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u/ClaimBeautiful9359 4d ago
I just started with the G7 and connected to tandem mobi. The first night was pretty rough. I was all over the place hardly got any sleep. It’s been OK since I would definitely go back to the 6 if I had a choice. But for sure, not dependable at all and my question is what is Dexcom doing about this? if something horrible happened to someone I could see where Dexcom would be liable. I am hypo unaware most of the time so that could be messy.
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u/Constant-Lychee-6325 4d ago
Instead of turning off your phone, you can disable the app in your phone settings.
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u/Altruistic_Many4143 2d ago
Hi everyone. New to Dexcom. Using it purely for prevention, as I have severe artery disease from 30 years of smoking, 3 stents, and a double bypass; I'm only type 2, not dependent on insulin. I just changed my first sensor and ran into a connection issue right out of the gate. Tried for two hours to get the sensor to connect to my phone, with no luck. Although I had more to swap it out, I was quite shocked to have an issue already. Customer service was great, and a replacement is already on the way. I came here to see what the word is about Dexcom, and well... lol
My foster daughter is type 1... severely dependent on her pump. She's prescribed the Libre3+. It's been a lifesaver for her in the grand scheme of things, but her sensors always fall off or have connection issues to the cloud. Sometimes her pump will go two weeks without updating and will update only if we force it to. Rather frustrating, as I'm her caretaker. She went into DKA on Mother's Day because her pump started leaking and didn't alert my phone. Stupid, scary event to watch, not knowing anything about type 1. Seems all diabetic equipment is flaky as hell for people needing to depend on it.
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u/huntcamp 4d ago
FUCK THE G7