Dexcome G6 randomly inaccurate

I’ve been on the Dexcom G6/Tandem TSlim combo for several months, and I love it! I’ve loved not having to calibrate my Dex (ever!) and I love that I can trust it to be accurate. Now with the Control IQ tech, I’m feeling pretty good about my sugars most of the time.

However, in the last month or two, I’ve had a new occurrence. (I believe this has happened four times.) My Dex suddenly tells me my bg is dropping crazy fast, and then, of course, it starts alarming at me because my sugar is 50 . . . 40 . . . LOW! Well, I don’t feel low, so I use my finger-stick meter, and what do you know? I’m sitting in the 90’s just fine. I calibrate my Dex, and it takes anywhere from half an hour to several hours to figure itself out, and then it works fine.

Has anyone else had this? This used to happen sometimes with the older versions of Dexcom, but I guess I’ve gotten used to the accuracy of the the G6. Just curious if anyone else has had flukes where it’s suddenly inaccurate.

Hi Abigail @AbigailL , I too really like the Control IQ, staying in-range using the “hands-off method” - other than counting and entering carbs.

I never had to calibrate a sensor until two weeks ago and in retrospect, I blame those false-lows on my activity. What happened, I work outside in the Florida heat doing construction/reconstruction on weekends, and two weekends in a row I was doing much bending, digging, lifting and straining. I examined the sensors that I was replacing a few days later and found that the very delicate platinum wire looked “crinkly”. Interesting that one of those sensors fixed itself and went on to last the full 10 days.

Hi Abigail,

The last 48 hours, I have experienced inaccurate readings, sensor errors, after starting the sensor, says change sensor. Also, found out my Apple software hasn’t been tested for iOS 14.4, however, they are compatible to Apple IPhone 11, I don’t get it. Not sure what to do.

Hi @AbigailL . There are some discussions on compression lows you might find helpful.
Search results for 'Compression low' - JDRF TypeOneNation Community Forum.
Essentially if you’re pressing on your sensor - typically from lying down on it - something about the interstitial fluid causes a low reading, which returns to normal once the pressure is released. That’s a very simplified version of my understanding - please check out the search results I shared for explanations from people with a much better grasp.
Another possibility could be placement of the sensor combined with exercise. If I wear my sensor on my thigh and do a lot of walking, bike riding, or leg lifts, I’ll show a quick drop, or it might show sooner than if on my abdomen. Likewise if it’s on my arm and I lift weights.
Occasionally I hit a bleeder when I insert my sensor. A little bit of blood may not cause a problem but sometimes it actually bleeds through the tape😱 (I don’t know until I remove it, because I place a cover and patch over it for extra protection). I don’t get a “change sensor” message but after the warmup I get multiple requests to enter readings, at which point I call Dexcom.
They will replace sensors that give you issues so be sure to call each time.

@Nadia575 Hello Nadia, and welcome to the JDRF TypeOneNation Forum! Note that this Topic string is rather old, inactive for a year, and you may not receive many replies.

How do you know that your G6 readings are inaccurate? Are you comparing them to BG Meter readings, and if so, are you doing the comparisons properly - taking into the differences between CGM interstitial readings, BGM blood readings, time-lag, designed meter inaccuracies, CGM arrows, etc. Also, you didn’t say for how long you have been using this sensor.

As you probably know, a Dexcom sensor may not deliver accurate readings during the first 24 hours. And as Dorie @wadawabbit mentioned, sensor placement can make a difference in how well the thing will work.

More importantly, like most manufactured devices, not everything works well at all times - Dexcom isv aware of this and will assist you. If you haven’t already spoken with someone at Dexcom, I urge you to call soon; the tech will take you through a list of check questions, and if the sensor is continuing to miss-perform, send you replacements.

Hi Dennis,

Yes, I compare with my BG meter. I have been using DexcomG6 and sensors for 45 days. The sensors have not lasted the full 10 days typically last about 5 days, received replacements from Dexcom. Right, now I’m out of sensors had sensors errors asking me to change sensor each day since Fri Eve 3/12. Used 3 already too soon to be changing. The pump has been working.

Thanks, Nadia

Hi @Nadia575 . I’m so sorry to hear about your frustrations. This may be a longshot but I wonder if am issue with your transmitter may be causing the sensor errors? Granted the transmitter has its own alerts (such as a low battery) but maybe something else is going on. A couple more thoughts: here is info from Dexcom re medications that may interfere with the device. I hope Hydroxyurea does not apply to you and you can skip it. Earlier systems said to use painkillers without acetaminophen. Some of us were happy to hear you can G6 use it with the G6 - but that’s true only up to a point.

Interfering Substance Risks
• Hydroxyurea Precaution
Hydroxyurea is a medication used in the treatment of diseases including cancer and sickle cell anemia; it is known to interfere with readings from your sensor. If you are taking hydroxyurea, your sensor glucose readings will be higher than your actual glucose, which could result in missed hypoglycemia alerts or errors in diabetes management, such as giving yourself a higher dose of insulin due to falsely high sensor glucose values. The level of inaccuracy depends on the amount of hydroxyurea in your body. Do not use your Dexcom CGM System
for diabetes treatment decisions if you are taking hydroxyurea. Talk to your physician about alternative glucose monitoring approaches.
• Acetaminophen Precaution
In previous generations of Dexcom CGM systems (G4/G5), acetaminophen could affect your sensor readings, making them look higher than they really were. However, with the G6, you can take a standard or maximum acetaminophen dose of 1 gram (1,000 mg) every 6 hours and still use the G6 readings to make treatment decisions. Taking higher than the maximum dose of acetaminophen (e.g. > 1 gram every 6 hours in adults) may affect the G6 readings and make them look higher than they really are.
Follow G6 instructions. If you don’t, you could have a severe low or high glucose event.

[Bold is mine]
And at the risk of stating the obvious (please forgive me!), do you doublecheck to make sure the sensor is snapped in completely? When I upgraded to the G6 I wasted a couple because I only pressed the round end. Now I do the narrow one as well.

Nadia @Nadia575 , did the Dexcom Rep provide you with any insight as to what might be causing erratic G6 readings?

When calibrating [very rarely do I do this], or vcomparing my BGM and CGM readings, I never use only the displayed number on the CGM, but rather look at the preceding 4 CGM readings and more especially the arrows displayed; this takes into consideration the “lag factor”. For instance, if my G6 is reading 120 mg/dl with two arrows pointing up, I expect my meter to read at least 165 mg/dl - two “up arrows” indicate BGL is increasing at a rate of 3 mg/dl/m or faster. A G6 lags behind a meter by about 15 minutes.

45 days is a good test for you to know if the Dexcom CVGM is suitable for your body. Unfortunately, it appears as if [just my thought, your doctor will help you decide] your body is not suitable for use of this device. But fortunately, there are other CGM devices you might successfully use.

My dexcom G6 can drop rapidly especially after I exercise. I can find I’m in the 40s and 50s without realizing it except for the pump alarms/vibration. I use my BG meter to calibrate and treat with glucose tablets/OJ. My BG meter shows when my BG starting to rise in 15-30 minutes. The sensor lags behind significantly. I calibrate it frequently to stop the alarms until I reach 110. I’ve been decreasing my I:CHO ratio, limiting the length and intensity of exercise, but I’m concerned about going too low! Any suggestions when one isn’t that aware of going low and if needed how to gain emergency care if out and about alone? Is it reversible? Might anyone be willing to share similar experiences and solutions? Thanks!

@Janine83965 Welcome Janine to the JDRF TypeOneNation Forum! Happy to have you here and joining in these conversations. For the most part, members on this Forum are not medical professionals and offer “tips & suggestions” based upon lived experience with diabetes. You brought forward a couple of concerns with which I’ve had experience and will comment:

Exercise: This is a concern to many as exercise can have many effects on diabetes. Aerobic exercise, even very mild, will often drop BGL [Body Glucose Level] and is often difficult to notice while being active. A key to help minimize BGL drop is to plan ahead, either by assuring that Glucose is “higher” before beginning, or to take less insulin before hand - sometimes by doing both. If you use an insulin infusion pump, it is advisable to either suspend basal insulin for a period before beginning exercise and continuing into exercise. I use a pump Profile that provides me with both less basal insulin on days of exercise in addition to using a less intense I:C ratio [such as, 1:18 in place of 1:15]. Anaerobic exercise can elevate BGL during and shortly after exercise, and then cause a severe BGL drop 4 to 8 hours later [my experience]. Always have a good source of glucose with you while exercising, and take periodic breaks to check and treat.

Hypo Unawareness: This can be scary, and the best path to take is training yourself to be aware - difficult but possible. It is always important to have carbs with you - 60 years+ ago, I always walked about with a pocket full of wrapped hard candies. You could try using “bio-feedback” methods to help train your brain to alert you; this is what we did in the “olden days” - I had diabetes and managed insulin for 30 years before the invention of digital glucose meters. Be aware that your symptoms of low glucose can differ from what is written in the books, so it is for you to get to notice your symptoms - If uncertain, my thought is to eat something if I “think” I’m low because it is much easier to bring a high back in line than having to rely on yourself, or someone else, to get you up from a low.

Good luck!