I had a (thankfully) rare episode yesterday and I wonder if it’s happened to anyone else. It was the last day of my Dexcom sensor and I hadn’t done a fingerprick test in a few days.
While I sometimes spot check my dexcom, my experience has been that it needs lots of checking for the first 24-48 hours, but, after that, if it’s a good sensor, I’m all set and the fingerpricks and dexcom readings are reasonably close. (I’m not as much as a stickler as others who have posted. I’m happy if it’s within 5 or 10 points in the sub 100 range and within 20% in the higher ranges.)
Anyway, for a good 24 hours I was flatlining and felt good. In retrospect, I should have realized that my reading were maybe a little too good, but it wasn’t so far out of what I was expecting as to raise any suspicion on my part.
I let my sensor expire and put in a new one. My last reading on the old sensor was 113. Half an hour later, I did a contour fingerstick test and it was 350!!! I think it’s very likely that during that half hour my blood sugar was rising. I had been walking around and Control-IQ had lowered and suspended my delivery a few times. Plus I had eaten without bolusing (mea culpa) – around 25g carb. But, I don’t think it could have rocketed from 113 to 350 in that amount of time . That 113 reading had to have been a good 100 points lower than the real reading. Or did it?
I was pretty alarmed and wondered how long my sensor had been reading lower than my actual readings. I tested for ketones and had none. My blood sugar came back down. All is well.
But my trust is a little damaged. I still love my dexcom, but I guess I have to view all that effortless flatlining with more suspicion next time.
I realize this whole story is a little convoluted (the half an hour gap between my final dexcom reading and my contour fingerstick test means there’s no direct comparison.) And I’ve definitely had many many cases where I tested half an hour into the warm up session and the results made perfect sense given my last dexcom results and many many cases where I’ve spot checked my dexcom during different days of the 10-day session and it’s been pretty much on the nose.
I guess my questions are:
Do you think I’m underestimating the terminal velocity of a blood sugar rise – could it have gone up about 250 points in 30 minutes?
Has anyone else had a case of suspicious flatlining. I.e. a Dexcom sensor that’s not jumpy or new but that just keeps telling you your in a range of 70–120 a little effortlessly?
If it had been off for all of my 24 hour charmed spell, would I have had ketones?
It’s more likely the basal suspend plus carbs w/o bolus caused 350. I often do bolus after CIQ suspend, to avoid highs, even when no food eaten. But with food, bolus for more than just food carbs, basically to replenish basal amount lost during suspension.
Never thought to do that. It is not uncommon for me to go up to the 200s within 15 minutes if I miss bolusing and consume 25 carbs. Basically, I go up into the high 100s and the 200s, sometimes even 300s, right after I eat even if I pre-bolused 30 to 45 minutes before I eat. And that is frequently after CIQ had suspended basal for a time. This even happens on occasion at night when I hadn’t eaten in 6 to 8 hours. I have been puzzled by that. But now it makes perfect sense.
One reason is that there is more insulin resistance when chasing a high BG, fueled by food digestion. And if preceded by a low, liver is triggered to dump more glucose, for additional rise. CIQ can eventually catch up, but I prefer to jump start with bolus. And easy to eat a few more carbs if needed.
If doing low or lower carb eating, many need to bolus insulin for proteins, fats. Search for TAG - Total Available Glucose.
The more I think about it, the more it seems possible I was just at the beginning of a “hockey stick” type upward curve and the last Dexcom reading might have been a slightly lagging indicator that that’s where I was heading. (I had been in the 90s for about an hour before then).
It was alarming, because while I see blood sugars in the 200s regularly, seeing a number starting with a 3 is rare for me.
Thanks for the advice. I have to keep those suspensions and reduced basals in mind when I eat and bolus(or stupidly fail to bolus)
I’m also happy to think that I was really flatlining up until that very high reading.
The accuracy of the glucose source that feeds any automated insulin dosing system is crucial. It doesn’t have to be pin-point accurate but must be dependable and not grossly wrong.
When the Dexcom G6 came out with its “no calibration required” claim, it encouraged people to adopt a personal no finger-sticks needed policy. I sometimes read the pride people take in avoiding all finger-pricks when using a CGM.
I didn’t for a minute buy into that aesthetic. There was a time when I did 10-15 fingersticks each day – that was pre-CGM but that frequency taught me that finger sticks were not that big of an inconvenience.
I now only test on average 5x/day but some days I only test once and other days, like day 1 of a new sensor, I may test 7 or 8 times. I have been burned too many times by an automated system over-dosing insulin based on a sensor feeding the alogorithm an erroneously high value. Or the opposite, when the CGM is reading too low and holding back on giving insulin.
Dexcom does warn us that we need to fingerstick if our symptoms don’t match the CGM number or if we doubt the number displayed for any reason. Seems that advice gets lost in the “no calibration required” marketing hype.
I think I could have been fooled by that wonderful flatline and I certainly understand your wanting to believe it. I fingerstick every morning just to confirm the CGM accuracy and I also use that number to calibrate if it’s off by more than 5 mg/dL.
I believe that current CGM performance is just not good enough to let it run the show without regular (as in every day!) confirming fingersticks. That old adage, trust but verify, certainly rings true in this context.
For those who are stingy with their fingersticks, especially those who use insulin pumps with algorithms, I encourage you to do a few more fingersticks.
I think a lot depends on how tight you want to keep your control. If you are OK, to have a GMI/A1C in the 5.7% to 6.5% which is Nirvana for most diabetics, it is totally acceptable to fly sans fingersticks. I fingerstick once or twice after a new sensor insertion but virtually never beyond that. I don’t do any calibrations but if the sensor is out by 20+ points, I just take that into consideration as the week goes on.
My GMI/A1C runs between 5.5% - 6% on Dexcom and my labs read about .5% lower since being on the G6. With the G5, my labs were running = to .5% higher than my labs.
When retired, I may put more effort into even tighter control, but at this point in life, I am totally comfortable with good, not near-perfect control (= to a non diabetic).
Nope, for me a digital pen that doses in 0.1u is much more convenient so stay on MDI. Only requires 2 endo visits/year to satisfy Medicare instead of 4 with a pump and crisscrossing International date line raises heck on pumps and other automated/semi automated systems.
I’m fortunate that the Dex G6 works incredibly the me. I reliably get 30-40 days of wear, and the accuracy is spot on … until it reaches the end of it’s life and it isn’t anymore. But that’s really obvious. My graph looks like it’s doing acrobatic jumps and twirls at the end of sensor life. I’ve never seen it just read flat and drastically off.
I used to test often while wearing the CGM, but have gradually learned to just trust it, unless I feel otherwise than what it’s showing. After countless numbers of times seeing Dex match right up with my meter, it starts to feel futile questioning it. Now I test 2 or three times after a restart for calibrations, because restarted sensors read dreadfully high. I will usually test once more the next day, just to make sure the calibrations stuck. Aside from that, I rarely ever test anymore, and feel confident trusting Dex
I am amazed at the number of people on Facebook who claim that they never use their meter and criticize those of us who calibrate our sensors. They are adamant that we are doing it “wrong.” I rarely use a meter after the first 24-30 hours of a sensor and that works for me. But it is a rare sensor that I don’t have to calibrate over the first two days. It is quite unusual for me to have a sensor that starts up close to my meter reading. If I don’t presoak the sensor, it usually reads LOW with double arrows down within the first few hours of activation. If I presoak it, it sometimes reads low and sometimes reads high. And once in a blue moon (maybe 1 out of 10 sensors), it actually starts up close to my meter. That being said, all of my sensors make it to 10 days while I have some D-friends whose sensors reliably fail at Day 7-8. Dexcom understands that our body chemistry affects some of these things. Most people on Facebook don’t…. I have my fingers crossed that G7 works better for me than G6. But except for Day 1-2, G6 is mostly good for me. Says she who started her diabetes career peeing on sticks.
I will easily rise to 350 if I didn’t bolus for 25 carbs.
Given that, the first 48 hours I am usually refining my Dexcom sensors, especially if it’s a brand new sensor. But I find they stay pretty stable after that. Since I restart mine it is obvious when they start to go as the readings become way off and it starts to lose connection a lot. If I am not suspicious I will wait to check it until about day 5 again and if it is still staying accurate I have a tendency to not worry about it.
But if I am ever suspicious, for any reason it gets checked and if it’s not within 5 points at the lower numbers it will get checked until I either switch it out or it is calibrated to consistently be right. There’s nothing I just about hate more than finding out I am 140 when I thought I was trending at 100. Or to eat because I thought I was at 80 to find out I was really at 120. So I am not above checking it a lot if I think it’s needed.
It’s absurd not to check them the first 12-48 hours, they can be way off especially when you start a new one, and then never calibrate it??? I remember once going to bed with a new sensor that wasn’t that far off, maybe 20 points, so I left it alone when I went to sleep thinking I would wait to calibrate it in the morning because it would be changing anyways. I woke up to it saying I was 180 and immediately dosed for it as I get DP sometimes…and then remembered new sensor. I checked and sure enough I was around 100…sigh, then I had to eat something.
This is a good example for “it’s different for everyone”. My fingerstick tests are so close every time I test, unless it’s rapidly changing or I’ve been lying on my Dexcom, that I’ve given up on checking /calibrating completely.
I rarely reuse sensors though, and when I do, I find readings aren’t as close after restarting.
When the transmitter is nearing the end of its useful life, the Dexcom does read more erratic, however, which no amount of calibration fixes.
TNYC, a few thoughts on what you talked about, not answering your questions tho)
agree on carb raise as 25 grams of carb to me = 100 points
agree with MM1 on covering some after a basal suspend
if your first 24 hours are off, try putting the sensor in 24 hours EARLY -don’t connect the transmitter until it has warmed up or “wetted” & the current one is done. Has worked for a number of folks.
Happy learning!
