CGM mixed reviews

I used Dexcom CGM for about a year. Overall its pretty easy to use. The results however were not so accurate. If you are using CGM systems, please make sure to check you CGM results against a blood glucose meter. Also, BEWARE of how DEXCOM bills you and your insurance. My initial order of DEXCOM went through CareCentrix, a durable equipment supplier for DEXCOM. Total cost was over $1100 of which I was responsible for approximately $550. My next order was processed through the DEXCOM Pharmacy and my out of pocket costs dropped dramatically to around $130/order. Even after many letters and telephone conversations, customer service at DEXCOM was unresponsive to trying to resolve the different billings. Because of this POOR customer service incident with DEXCOM, I have stopped using it (I prefer to deal with companies that are helpful & responsible to their paying customers, not solely to the almighty dollar). Others have followed suit.


Really sorry to read about your issues with Dexcom. Can’t say that we’ve had problems with billing. However, we have noticed that it can be off greater than 20% in either direction. So we definitely have our daughter check her bg often. Dexcom does give us peace of mind in the evening and while she is in school as we can see when she’s dropping or going high. Just curious if you found a replacement CGM since taking off your Dexcom.

What amazes me the most is that the sensor is in touch with actual blood (or very close), so why is a regular blood glucose monitor so much more accurate than the DEXCOM? On another note, the fact that you are monitoring blood sugar spikes for someone else make the DEXCOM useful, but it was just not worth it for me. My readings were about 25-30% off at times and I just didn’t feel comfortable spending extra money on something with results like that. I am sticking to the old school meter until something better comes around.


Certainly sounds like you have not had a good education training on how the CGM product works. Your are NOT to use the CGM as a BG Meter testing replacement for insulin dosing. All the safety/product information for all the CGM products very clearly state this. When you talk with support (I use a Dexcom) they always tell you to NOT use the readings from a CGM device for dosing.

The CGM products give you excellent “trending” information so that you can then follow up (as needed) with a BG test to verify and then take steps necessary if you you need to correct for lows or highs.

I’m not aware of any CGM company providing assurances that their trending results with ‘match’ a CGM reading.

Also the readings between CGM and BG Meters are NOT using the same source of fluids for the results provided. The CGM sensors are not using blood for their readings. BG meters are using a blood droplet for their readings.

Have you taken blood readings from your forearm and compared that to sticks from from fingers (multiple fingers?) … you will find they vary a fair amount. The same blood droplet providing tests on two strips to the same meter at the same time will provide different results and if you start comparing BG meters you can really get confused. The accuracy of BG meters is miserable and is very slow to get better by the meter manufacturers as they are going on the specifications set forth by the FDA (I’m pretty sure that is the government group) which sets the allowable deviation limits.

I started wearing CGM products with the Navigator many years ago before they stopped providing product here in the USA and I’ve worn the Dexcom starting with the System Seven over 5 years ago. I’m awaiting delivery of my G5 system now.

Many of your comments are uninformed about what the CGM does and your understanding of how it truly works. It just seems to me that your medical support team that prescribed the CGM for you has not helped provide a good education for you with the CGM.

Do some study and research and you should be able to better understand the CGM and its capabilities and uses.

I wear mine 24/7, I’m on Medicare (insurance does not cover CGM under Medicare) and my wife and I do all we can to afford the CGM as it has saved my life more times than I can recall since wearing it.

One thing I found to greatly improve the accuracy of my Dex was to switch test strips. Up until last spring, when my CDE happen to mention that test strip accuracy varies greatly I decided to switch. I switched from One Touch Ultra to One Touch Verio. The verio strips are much more accurate & therefore when I calibrate my Dex it too is more accurate. You can do a search on test strip accuracy to see where your strips fall. Good luck.

I find the Dexcom amazingly accurate. I do bolus according to the readidngs. I think it depends on where you insert the Dexcom. It did not work well on my upper waist or on my stomach as they recommend. I use it in my thighs, slightly toward the inside. I have more flesh there. I can wear it for two weeks. Some people go longer but my insurance covers them so I change at two weeks. I now have the G5 but the G4 was just as accurate.

I agree with Nolan. I think there is a lot of misinformation or uninformed statements being made above. If you know what CGM technology is, how you use it, and what it is reading, the data makes a lot more sense. I’d urge you to do some more research, you may even decide to give it another shot, and if not, that’s not a big deal either, I’d just hate for someone to see the post above and decide not to use CGM based on the misinformation above.

Dexcom’s and other CGMS do work well for some people, and some people do dose off them despite the warnings.
However if you find your Dexcom is out by 20% or if you only use it for trending, then try the PredictBGL App. It is a dose calculator that also predicts future blood sugar levels. In many ways it is like a pump + cgm combination. Obviously it does not inject.

CGMS do not measure blood glucose - they measure the glucose in the interstitual fluid (between your fat cells baby!).
Since they measure something totally different, we shouldn’t expect the results to be the same as a fingerstick BG.
The CGM justs gets re-calibrated periodically to your fingerstick BG so that the results look the same as your BG.
The results do tend to drift away from the actual BG value over time, and of course there is lag - it is 5-8 minutes behind the actual BG.

I’m curious about how the commenter here determine accuracy in BG readings, whether that’s using CGM or a meter.