Anybody using 505 software update yet? Is it that much more accurate?

I'm curious how this compares to the current software version. My daughter, who is 6, has been using Dex since October 2013, so she has the adult receiver. Technically I could download the 505 software and use it, even though it's meant for adults only (since that's what the trials were on and what was FDA approved).

The one problem we have with the Dex is when she goes low, as in 40s or 50s. If the Dex goes that low, it takes FOREVER to catch up to her actual BGs as measured by a finger prick (can be up to an hour to catch up). Dex has been nice to have to see trends and sleep through the night, but it hasn't been as accurate as I was hoping. So the 505 software upgrade, with its improved accuracy, is naturally appealing to me.

There is a whole thread on this, located here, with people's experiences:

I ran the old and new at the same time on 2 receivers and made the spreadsheet
posted here:

As you can see, it was slightly more accurate and within about 9% of the fingerstick on average, as they claim.

The first day sometimes has larger errors.

What I do when the Dexcom is slow to catch up as you describe (after a low) is enter the new fingerstick value to recalibrate. That catches it up faster.

Yes I am using the 505 version and have been since it was introduced. It is more accurate and seems to recover more quickly from lows. I was reticent to switch and had 2 receivers so I updated one and left the other one using the old version. The newer software was far more accurate so it didn't take long before I updated the other receiver as well.

Thanks for pointing me to this discussion. I just read all 8 pages! It seems all over the place, with half the people saying the update is worse and the other half say it's better. I didn't realize 505 has been available since last November - I missed the memo, literally! That's about the time my daughter started having terrible skin reactions to the Dex and we haven't used it much since then.

What's disheartening is that this is supposed to be the AP algorithm, and I would expect more consistency in terms of personal experiences. Your spreadsheet was only for a few days - how has it been for you in the long term now?

Thanks Clare. If we go ahead and get a new receiver, maybe we will experiment as well. Since my daughter started on Dex before it was approved for peds, she has an adult receiver that can be updated with 505. A new one would be a ped receiver and not eligible for the update.

I am quite happy with it, and like Clare says below, I stopped using the old g4 version. While I am no longer keeping the spreadsheet, it seems to be more consistently close to the fingerstick values than the old version.

These things will never be perfect as they don't measure blood glucose, they measure interstitial glucose ( the "juices" surrounding the cells). But it is getting pretty good. Dexcom will try to get FDA certification for insulin dosing at some point...whether it is this version or the g5 or g6, I don't know.

Canada's accuracy for the dexcom seems to be 13-18% accuracy. sigh. but still is valuable to me. I have asked when we will receive an update or the bluetooth receiver. always get the same answer they have no idea when that would be. sigh. I want to be able to use my phone with it. sigh again. Just be lucky with your accuracy American's. they seems more accurate right now then here in Canada, I am however not really complaining as it is a vital source for my diabetic needs. I do have a question though, what is your high alert set at?

The new MARD score for Dex with the 505 update is 9% it is the only single digit MARD for any CGM. Many of the D parents in my Dexcom group fall into the same category as you. Their kids started on Dex well before it was approved for peds. They have updated their adult receivers and found if they're running both the adult receiver is closer to fingersticks. I'm fairly certain though that since this software update has probably been in the pipeline for at least a year or two much of it is already incorporated into the peds receiver since it was only approved just last year.

Dishers, my high alert is set to 150 or 8.3 mmol. I have my snooze set for 60 minutes so once I know I have reached my high I don't get constantly buzzed while bringing it down. It helps to keep me sane and not panicking. My low is set at 70 or 3.9

ok, that is about what mine is, same for low but my high is 8.9 wanting to bring it down a bit. so was curious to what others had it at. Thanks clare

Thanks Clare... I am currently using 2 receivers (for the weekly overlaps, thanks to your suggestion last year :-) and plan to do the same when my insurance okays my new receiver (since both my current ones are now out of warranty).

That way I can see if the 505 works better for me, or not.

bort269 I've been using the system continuously since November 2012 and I have regained some hypo awareness and now have a really good sense of where my blood sugar is even without looking at the receiver. It's always on my belt in a tallygear case but I have long gotten past the need to continually consult it. I rarely use the 2 receivers anymore because the 2 hour calibration time is not fraught with the omnipresent threat of hypos. This is credit not only to Dexcom but also to Omnipod for making D a whole lot easier for me to manage. My insurance has okayed my new receiver which this time will be pink, but both my previous receivers are still working. My sensor is on day 33 and until 2 hours ago was still giving consistent, accurate readings, but it has gone to ??? so I'll probably change it out. I did get 286 readings yesterday.

Have you tried Flonase spray underneath the sensor ? Apparently this has worked for multiple people who were having Dexcom adhesive allergy. I believe Nasacourt is the same stuff as well.

I had the old software and got the new 505 software the day that it came out. It really is a lot more accurate and responds much more quickly to changing glucose levels than the old one did.

wish Canada had it, and the bluetooth, think I have said that already. lol

My CDE updated mine for me 2 weeks ago. I think it’s a bit more accurate but I still have tons of number 10-20 points off. And much worse 50 or more. I also have trouble whenever my glucose moves etc and with low recovery. It shows me going down after a low. Also things like it says 107 and I’m really heading up at 130- it’s really a pain because at that point I would be stopping a high possibly. So I still have to do tons of testing.

10-20 points away from 107 is still well within the standard for accuracy. Dexcom is for trends only. It is extremely rare that my Dexcom and my meter are absolutely the same, and that is most often after an 8 hour flatline or and uneventful night. There is always going to be a time lag between Dex readings and BG meter readings because they're not reading the same fluid. With only calibrating when it asks or when it's more than 20% off I have managed to shorten the lag to about 5 minutes, but it is still there.


Also, people forget that the test strips are only required to be +/- 20% of the true value 95% of the time (i.e. 5% of the time it can be even more off). So if your blood glucose is 100 as measured by a laboratory standard meter, your test strip could read anywhere from 80 to 120 and still be OK by the FDA standards.

For some reason people tend to think the test strip is magically spot on - it isn't - it is an approximation too. And this is what is used to calibrate the DexCom!


I have no issues with 10 to 20 points different from a meter reading, I can do two back to back fingerstick readings and get even more variance than that. Always have. I concur with previous comments.

When I do get greater variance where readings are are more than 20% off I’ve also learned the hard way that more often than not Dexcom is correct and the fingerstick was the error. Now I do a second fingerstick before assuming Dexcom is wrong.

I agree that is the accepted discrepancy and I understand it's reading off a different basis of course. But for me it doesn't matter if it is off 20 points or even 10 points sometimes although that is usually ok most of the time, and this goes for fingersticks too, that is too much because it makes a big difference to what I will do, especially if I'm dropping and it doesn't show that.

Unfortunately as I said I get tons of numbers worse than that... dex just had me going straight arrow in the 90's while eating when I was already climbing to 117- I could tell from my symptoms something was happening and I was worried I was dropping. I had a bad low last night it didn't pick up on, I was only 70 in finger sticks but I could tell from symptoms I was about to pass out, dex totally missed that one. That one came on suddenly with auditory symptoms while I was reading/typing, no real warning.

I'm beginning to wonder if there is something about my body chemistry or if this is just a good as it will get for some of us. If you're not unstable and cruise along with no problems it is ok but if you tend to drop or go up quickly it's not that great, but still, it's better than not having it at all of course imo, most of the time.

I know my test strips aren't spot on, I tend to do at least 2 sometimes 3 to see what is going on lately because of all the problems I've been having with vertigo and not knowing for sure if I'm going up or down.