Should a CGM be used for dosing insulin? Would you use a Dexcom output, instead of your glucometer, to dose for a meal.or to correct for a high blood sugar? I know a few Dexcom users who do this, but I cannot do that. Scar tissue can cause inaccuracies on my Dexcom, so I test before meals, and when correcting highs.
Dexcom Seeks Approval for Dosing Insulin
FDA to hold July 21 meeting. Why is an insulin-dosing claim important?
My daughter does fingersticks as little as twice daily, and that’s only to calibrate her Dexcom. I wouldn’t be comfortable with this if her Dexcom weren’t so consistently in line with her Freestyle meter. Even if the numbers are 5 to 10 points off, who’s to say the meter was the more accurate of the two? There, unfortunately, is a degree of error in the accuracy of meters (a lot more than any of us are comfortable with, I’d bet) that is allowed while still meeting accuracy “standards.”
I do the same as @rgcainmd. Dexcom is consistently accurate. I will not–however-- correct if there are suddenly abnormal changes in readings (high or low). I have found delta values +25 will quickly level out or sudden lows to be the cause of pressure on the sensor. Look at trends in general and we will double check with a finger-stick if we think something seems strange.
For my son Dexcom is very accurate. Except for the 1st 24hrs, we usually dose off Dexcom. I agree there are times a finger stick should be done but that is really no different than times when a finger stick is questionable and a second one is needed to verify.
We do it, but only when the Dexcom reading is within a reasonable range and there are no recent big swings.
I’ve been routinely dosing based on Dexcom readings. I have not found any good reasons not to do so (with common-sense exceptions of course - it is not too difficult to see when readings may be off). While at the moment this makes no difference to me, an official FDA approval is going to be a very important step in the right direction for a number of reasons: Medicare coverage, wider use in general, use with artificial pancreas technology.
I dose off of mine sometimes and sometimes not. I’d call it about half and half.
Like others, I will dose off of my Dex number when my CGM tracks my fingersticks well. If it’s a micro-dose of insulin or glucose, I’ll often make the move without 100% confidence in the reading since the treatment correction is small. Small inputs = small mistakes.
On the other hand, if the Dex number suggests a more aggressive correction, I’ll do the fingerstick since I don’t want to over-correct.
I find I am now mostly bolusing (MDIs) off the Dex. Over the last few months I’ve learned a lot about how my body responds to insulin and different foods, for example, I need to wait 45 - 50 minutes after bolusing to eat breakfast but also that I need to have my meal ready before that point so I catch the downturn in my BG. Generally, the trending information is more helpful to me than the single-point-in-time in figuring out when to bolus, too. But when the Dex data doesn’t make sense, I will definitely do a finger-stick (on occasion, more than one) to figure out the timing of my bolus.
I have been bolusing off my Dex when my sensor is a good one, and there has been good accuracy. My last two sensors have been duds and I have been doing a lot of fingersticks. The places I choose to place my sensors can make a lot of difference. If I was more agile, and without arthritis, I could use the backs of my arms, and other suitable places.
I treat lows based on Dexcom readings all the time but fingerstick gefore treating a high.
Also, be careful not to overdo a low correction–as it is a longer delay in Dex when coming up from a low. 
I’m a person who cringes whenever I read that someone uses their CGM, any type, to Dose their insulin. My Dexcom receuver and T:slim G4 are rarely in agreement with any of my 3 meters. Nor are they in agreement with the meter used at my endo’s office. So I would never agree with anyone in doing this.
The differences between my meter, the meter I use to calibrate my CGM can be up to 80% +/- from my meter. Not good. And I do not use anything that can alter my blood sugar levels. I do not calibrate the Dexcom receiver or the T:slim CGM when there are arrows.
So I always have to check to see if the CGM is correct. Thankfully I don’t often see the raising or falling arrows. I only got the CGM because my husband goes out of town for overnighter trips and I have never been able to tell I’m low while I’m sleeping, never since diagnosis in 1965. So my endo suggested I get one. Well it’s not so live saving when the CGM says I’m 132 and my meter says I’m 72. Yes this happened, not at night but during the day. My body signal told me I was getting low so I checked.
Clearly, it seems there’s some people for whom the Dexcom just won’t work. For others, like myself, I’ve found it to be very trustworthy. Outside of the first 24 hour startup period, and the day it starts to go wonky (I wear mine well past the FDA approved 7-day period by restarting the sensor, so have to keep an eye on it starting around day 12-14 or so, I’ve found), my Dexcom is generally within 10 points of my meter if:
But the thing is, I KNOW in all these circumstances that it is going to be different from my meter. By observing multiple finger sticks, I’ve even actually gotten fairly good at guessing how far off my Dexcom is going to be off from my meter based upon the rise/fall rate.
I have the same problem with some sensors, but then I do have sensors that are very accurate, and it would be appropriate to bolus from the CGM. I have decided that proper placement of a sensor on my body is crucial. I cannot use a body part where there is going to be pressure against the sensor + transmitter combo. My wide, heavy laptop pressing against my sensor causes problems, so I cannot use the tops of my upper legs. I can’t use the outsides of my legs because I sleep on my sides, and there is too much pressing against the mattress. I cannot use the part of my abdomen close to my belt since there is pressure there. I am experimenting with the inside sides of my calves, my upper ab, and chest areas, There should not be any pressure against my sensors there.
If I have a steady arrow and my Dexcom has been accurate lately and I have no reason to suspect it’s off (such as a super rapid change or a reading that doesn’t match symptoms or just doesn’t make any sense) then I do dose off my Dexcom.
It definitely seems that there are some people for whom the Dexcom just isn’t accurate. But that’s not the case for everyone. My sensor is on day 35 (longest ever) and the readings match closely (within 20%)—and I just restarted the sensor today, so this is technically the first 24 hours, which tend to be more inaccurate than the other days.
I dose off of my Dex G5. I find it to be extremely accurate and have gotten very comfortable with the readings. I also understand I’m the minority and that completely makes sense.
Question : do you regularly use 3 meters? If so, why?
I’ve noticed this too, Bradford1.
No, I don’t regularly use 3 meters. I generally use 2, one at the house then one is in my purse for when I’m gone, the 3rd is kept in my overnight bag. When I first started wearing the Dexcom and noticed how far off it was from the calibrating meter, I decided to check my readingS on all my meters.
Also on page 84 of the Dexcom G4 Platinum User’s Guide, at the top of the page is a WARNING box telling you not to use the readings from the Dexcom to decide how much insulin you should have. I’m sure if my readings were more accurate I’d use the CGM too.
No doubt Dex can be a bit wonky sometimes but I find by following the advice below directly from Dexcom the numbers are very accurate. Again, this is just my experience, I’m not generalizing here.
“You should calibrate when the system requires it or if the CGM reading is inaccurate. You can calibrate when you are asked for the two start-up blood sugars, and whenever the sensor is inaccurate. Inaccuracy is defined as when the difference between your sensor glucose reading and blood glucose value is greater than 20% of the blood glucose reading and blood glucose value is greater than 20% of the blood glucose value for sensor readings > 80mg/dL or greater than 20 points for sensor readings < 80 mg/dL”
I’m not suggesting everyone or even anyone dose off of Dex but as with sensor length they have to put that in there because it’s not FDA approved at this point. The User guide also says to use the sensor for 7 days and I regularly get (as many do) over 20 days out of each.
As always YDMV
