Your Most Accurate Dexcom Sensor Site


how long did it take you to figure this out for yourself? months? repeated locations?

also, if you were finding funky readings that did NOT match your finger sticks, would you pull off the sensor and try another location? try try again?

also, do you find that there is a “warm up” period before the sensor reads accurately? like the first 24 hours dont read well, but it settles in after about the second day?


For me, it is night and day difference or if it’s working well or not. So that might help you in your assessment.

My low back is my most accurate, and it gets dialed in pretty darn quickly. It might be off a little bit for amplitude the first day, but it tends to be pretty close to the money after day 1.

After joining FUD, I tried my thighs for a month. I tried my arms for a few weeks (and I had used them exclusively during my pregnancy in 2013 on a previous generation Dexcom with good results), and I tried my abdomen for a few weeks. I initially thought my legs were okay but just needed to calibrate more…but I never really saw better than vaguely-sort of-not really-accurate results. It might show the general correct direction, but it lied to me a lot (on numbers and on direction and speed). I wonder if the Dexcom was getting into muscle and it confused things. My arms weren’t great either…but I want them for my pods anyhow. My abdomen was a hot mess. Those sites bled more easily and that’s probably the problem there.

If I knew the site had bled a significant amount and the readings didn’t get more accurate after three days, I pulled it and tried somewhere else. The others I let ride for the sake of science and just went back to testing my fingers 8-15x a day.

When they work for me, they work like a dream. The ones that didn’t work after a day or two just probably weren’t going to pull it together, based on my observations of the ones that I let ride.


currently i test upwards of 20+ times each day. but it works. i really hope that the dexcom helps me, though. i would love to spare my delicate but very callused finger tips any more pain than i am already putting them through.

also, i am very very curious about results from the G6 model coming out. i want to hear what FUD members have to report on it. accurate or not?



i placed it on the outside of my upper left thigh. it has been close to accurate and then not even close to accurate. it tends to run low compared to my finger sticks. it woke me up all night with lows of 40s when in fact i was in my 60s. i have set it on the softest alarm sound that it has, and i still find it loud and somewhat annoying. made for a bad night’s sleep.

but it is comfortable and i dont notice or feel it. it was easy to insert. the sensor warmup session was a breeze. calibration is easy. i guess i am just going to roll with it on this site and wear it for a week to see if it becomes more accurate or if i should find a different site.

some of you have mentioned that sometimes the 1st 24 hours it can be wonky till it settles in, so i will be patient. i plan to swim tomorrow, so i am excited about wearing it in the pool and to see if it is comfortable.

my husband and my mother both want me to hang in there and make it work for me. they are both extremely encouraging, supportive and enthusiastic. ironically, my brother-in-law works in endocrinology soft/hard wear and is up on all of the tech stuff that we all talk about.

when i was at my endo yesterday, we discussed the 90 day implantable sensor. unfortunately, as soon as he said that insurance wouldnt cover it and that i would have to pay OOP, i opted out. is anyone here on FUD familiar with this implantable sensor?

looking fwd to hearing back from everyone for feedback, etc.



Way to go, @daisymae! I do try to start new sensors early in the day so that they hopefully are dialed in by bedtime. Sometimes it works, sometimes not. Looking forward to your updates!


i dont want to jinx myself, but it seems that the sensor is more aligned today than it was yesterday. hopefully yes, b/c i like the location of this sensor site. its very comfortable and is not disrupted or restricted by my clothing/sleep positions and will not be pressed in by my bathing suit. wouldnt that be just wonderful!!!


Here is link to discussion on implantable sensor. It was just approved, so not sure if in use yet in US.


thanks for this. i found it very insightful. i was actually at my endo this past friday, and it was one of the topics that we discussed. however, medicare is not covering it (yet) so i would have to pay OOP. the minute he mentioned that i decided to stick with my decom. :wink:


I find that sometimes if it is still wonky at 8-12 hrs in, it may pay to stop and restart it. It seems better at that point with a fresh start (bypassing the variations in the first 12 hrs). Sounds great that you’re getting it to work for you!!


you are the very first to make this suggestion to me. was this something that you came upon on your own, or was it passed forward? do you find that you need to do this frequently?

also, i have noticed that although sometimes today the dexcom matched up within a few points with my finger sticks, but at other times there was about a 15 to 20 point difference; is this “normal?”


I don’t restart it early that often, but occasionally. I think I got the idea from something posted either here or on TuD, but not sure. 15-20 may be “normal” (depending on where in the range), but the other possibilities include:

  1. variation in your finger stick meter, unless it’s one of the best (eg. Contour Next)
  2. lag between blood and interstitial fluid bg levels
  3. skewed errors between meter and cgm

usually it does continue to get in more consistent agreement as time goes by.


Another personal perspective and context if it is of any use. I am very lean and do lots of exercise; MTB, weights, running and pretty much anything active. I’ve been using the Dexcom since the G4 first came out and my responses have been consistent for both the G4 and G5, some of the things I have found:

  1. I can’t use lean active areas. I have tried dozens of sensors in calves etc and either can’t get readings at all or they die quickly, on removal, the sensor tip looks damaged / bent. This happens even if bunching tissue on insertion.
  2. Abdomen works, fairly accurate, but doesn’t last long. Sometimes only a few days, I guess this is due to activity. The best abdominal site for me is lateral abdominal / superficial to the obliques which lasts a bit longer with a generally good accuracy, although not as good as arm sites.
  3. I have tried numerous arm sites and the key sites for me are the posterior lateral arm (not the posterior arm). For the best results I press my arm to my side and rotate slightly to “bunch” the tissue in the area I am going to use and do a very quick insertion. These sites are incredibly accurate for me and even pick up fast drops when I’m out mountain biking, they last 14 days plus, I usually change at 14 before there are any issues with the sensor. The only negative for me with these sites is that it interferes with my sleeping position, so I tend to avoid sleeping on the side its on to avoid compression lows at night. I use liquid skin tack which I apply directly to the sensor adhesive, so no issues with it not sticking.
  4. Low back and gluteal region - I have only tried a few sensors in each of these areas, for some reason neither worked which I didn’t expect. Probably not the best areas for me as they will get some compression during my daily activities so I haven’t tried more. Yet.
  5. You probably have heard this too, but calibration tends to be a lot more effective for me if BG is not only level but also straight lining around my normal BGs, so 5 - 6 mmol.

As an additional note, I should be trialing the implantable Eversense in the next month or so, it will be implanted for 6-9 months. I will obviously give it a review when I get it! :grinning:


I’ve read some people will “soak” their new sensor for 24-48 hours before starting it, and while still using the existing sensor. That way when they remove the existing one, the new sensor will have already acclimated to their body and will give accurate BGs right off the bat. Something to do with the sensor’s enzymes adjusting to the body. I haven’t tried that but am thinking to as the last couple of new sensors needed 2-3 days before giving accurate BGs :frowning:


I’ve read several postings where people say they do something like this to good effect. But Medtronic clearly says not to do this, because it causes hydrogen peroxide to build up in the tissue around the sensor, and that’s bad for the sensor accuracy. They say put a transmitter on the sensor within 5 minutes:

“However, you’ll want to connect your MiniLink transmitter as quickly as possible (within five minutes) after inserting the sensor to ensure optimal sensor performance. If the sensor sits under your skin longer than five minutes without the transmitter attached, a chemical reaction can occur and hydrogen peroxide can build up around the sensor site, causing performance issues. So avoid letting too much time go by between inserting your sensor and connecting your transmitter.”


Wow, thanks, never saw this before. I was only referring to Dexcom when referring to “soaking”. Best to research a further as to whether Dexcom sensors would have the same negative effect due to “soaking” as Medtronic has!


what is all this business about “soaking?” what is it and what do you mean by it???


i cant wait to hear about your experience with it and how accurate it is and how painful the procedure is. i just happened to be discussing this with my Endo on this friday, but the moment he told me that insurance doesnt cover it, i opted out.

are you doing this as part of a trial? or are you paying OOP?

dying to know everything about it!!!

good luck!!! :smile:


“Soaking” just refers to the practice of inserting a new Dexcom sensor a couple of 24-48 hours BEFORE your current Dexcom sensor dies (or expires). You insert the new one but do NOT start it. You continue to use your existing sensor 'til it dies, then stop and remove it. Finally, start the new one which is already inserted. This technique is supposed to acclimate the new sensor to your body so that you don’t have the 1-2 day inaccurate readings when starting a newly inserted sensor, as so many experience. As I said though, I haven’t tried it. A lot of DIY OpenAPS / Loop users do this because they cannot have the inaccuracies that come with a newly inserted sensor (since they are bolusing directly off the readings!). I may try it with my next sensor.


The creation of hydrogen peroxide is a byproduct of any sensor that uses the enzyme glucose oxidase, which all sensors currently do. The reaction is:


As to the issue this may cause with the sensor, that is a question for each manufacturer. There are many variables that could be effected.

In practice the first generation glucose sensors measure that Hydrogen peroxide to determine how much glucose is in a sample.


i may try this, too. i had the 24+ hour inaccuracies as well. it was very frustrating. i had the darn out-of-range alarms going off right and left. i didnt even bother trying to calibrate it b/c the direction arrows were always going either up or down; i knew better than to mess with it.

if the “soaking” doesnt end up working, i think i will just shut off the alarms until 24 hours have passed. they kept me up all night, and, as well, they drove my poor husband crazy. so it kind of ruined our w/end together 'cause we were both so cranky :wink:.