Can Anyone Explain this G5 Phenomenon?

Type 1 and LADA
21

I don’t notice any difference in the life of my G5 sensors from now to several years ago. I used to routinely go 16-21 days as I was trying to hoard sensors in anticipation of Medicare which didn’t cover CGM at that point. Another reason for extending sensors is the cr*p first day performance. If you use a sensor for 1 week, you have 1 bad out of 7 days. If you use a sensor for 2 weeks, you only have 1 bad out of 14 days. (I sometimes pre-insert sensors and it makes a difference but not always a huge difference.)

Now that I am on Medicare with no out-of-pocket cost due to Basic Medicare and my Supplement, I usually use my sensors 13 days. The reason for the odd number is that I like to restart my new sensor on my schedule and not get reminder alerts during the middle of the night. If I don’t wait until Day 14, I can insert a new sensor anytime on Day 13 with no reminders.

When I pull a sensor, it is usually working just fine. But I have an obscene number of extra sensors. The last couple of Medicare orders, I have indicated that I need only 3 sensors and despite the order saying 3 sensors, they still send me 5! There are rumors that Dexcom is trying to unload G5 sensors on Medicare people and sometimes I wonder since they send me more than I want or need.

One Medicare beneficiary on Facebook indicated that she didn’t order sensors every month from Dexcom because she used her sensors for 2-3 weeks. Then when she went to place an order the Dexcom rep indicated that if she didn’t use sensors according to Dexcom guidelines, they would cancel her Medicare coverage! So I am careful to order every month and indicate that I need sensors.

I plan to keep using G5 for a couple of months once I start getting G6 in order to build up a stash of sensors and transmitter life. I don’t ever want to be in the position of having to stop using CGM because a sensor failed or they don’t send a transmitter on time. I am anxious to start using Basal IQ on my Tandem pump and I hope that I have the will power to delay using G6.

2 Likes
22

It is a tough balancing act to keep A1C low and stay at 70 or above without going high too often either. Hopefully this problem will be fixed with the G6/G7. I have not heard this issue with the G6 users.

That is why keeping the GMI indicator in the clarity reports (near equivalent to A1C) below 6, critical focus will be on the Standard Deviation. An ideal standard deviation is 20 or less but life happens and not always possible to do that. Fine-tuning comes with time and a lot of patience is required with both the Dexcom system and the company to achieve the results of a non-diabetic individual while still making life about more than diabetes management.

2 Likes
23

Month 1 is a heck of a learning curve, but each baby step makes you that much more confident in shortly not wanting to go 1 day without Dexcom

1 Like
24

OMG, those arrows are your very best friend! For example, lets say a half an hour ago you were 250, then 15 minutes later you were 230, but now you have a reading of 175 and two down arrows. That means you are not anywhere near 175 but likely below 130 and dropping fast. Watch the arrows! Double arrows are not to be ignored. A slight up or down arrow generally is no cause for concern unless you are near being hypo.

25

Those of us who work hard to keep our BG in a normal or semi-normal range are going to run into more false lows with Dexcom than people who run higher. If Dexcom reads 10 points low when your meter says 150, big deal that your Dex says 140. But if your actual BG is 80, 75, or 70, then a Dex reading of 70, 65, or 60 can be problematic for endos looking at your Dex reports. Fortunately my endo understands that about 1/3 of my sub-70 numbers are probably not real lows.

Plus the nature of interstitial fluid is that it recovers from lows slower than blood. Thus the phenomenon of Dex screaming that you are still sub-55 and your meter says 96. Sometimes I’ll calibrate but it never fixes the problem. During the daytime I might just keep dismissing alarms until the difference resolves. And (bad girl!!!) I have been known in the middle of the night to turn off my phone (receiver) if I know I’ve treated a low and want to sleep.

Dexcom is not perfect but it is hugely better than no CGM or the first generation of Medtronic SofSensors. There is a learning curve to being successful with it and understanding the strengths and weaknesses. And sometimes just admitting that it was hugely wrong, calibrating and moving on.

Also, Dexcom techs sometimes advise the 3 by 15 minute calibration fix. Calibrate once, set a timer for 15 minutes and calibrate again. Then repeat. My understanding is that the last 3 calibrations affect your Dex readings and this allows you to reset the algorithm.

26

Oh Dave, I do watch the arrows, but not when calibrating.

I have never seen two arrows and hope not to!

2 Likes
27

Sorry, I should have read more carefully.

28

I suppose your right, Laddie. Thanks for putting that into perspective.

29

I’ve used the G4 since 2012, then the G5 for a year, and the G6 for the past 14 months.

I love them all, but with every single one of them, they falsely report lows in the early morning before I wake up.

I have tried everything, but Dexcom thinks I’m dying whenever I sleep (even though every single time I tested I was in the 90-120 range)
Because of this I resorted to turning off Low Alerts at night so it would only go off at (what it thinks is) 55.
The only problems this ever caused me was that I would sometimes forget to turn my Alerts back on in the morning!

With my G6, it’s still the same issue, but I can use the different alert time settings so it’s no longer a problem.

I know this isn’t your exact problem, but just wanted to let you know that CGMs aren’t perfect… but I wouldn’t ever give them up!

30

Thank you for confirming that you are also receiving false lows early in the morning. For a while I will continue to test until I am confident they are all false lows. I wouldn’t give up my G5 CGM. It is the best tool since the insulin pump.

31

@bort269 @rcarli I’ve also had this problem since my early days with Dexcom (G4s initially, G5 now).

I don’t place sensor where it’s impacted by compression lows, and have concluded that my CGM was 1.0 mmol/L low (18 mg/dl) due to morning dehydration. I’m on a diuretic at night.

32

Jim, I got through the night, but had a 5:30 am alarm low of 45. Finger stick showed 152 because I had to eat so much before bed in order not to have low alarms at night. I usually never have a reading of 152 in the morning. I assume this was a compression low. My control at night is worse using the Dexcom G5. I love it in the daytime, but not in the night. I need my sleep!

May I ask where you place your device so that you don’t get compression lows?

33

It really depends how you sleep. I am a side sleeper so can only place between belly button and xiphoid process (no more than about 1/2 inch either side of this direct line) to totally avoid compression lows. Also note cuddling a partner can totally stop signal between transmitter and receiver if transmitter buried in partner, or if partial can also occasionally create a compression low.

Getting nighttime to work properly is always more of a challenge than daytime.

34

@Marilyn
I’m a side sleeper, however CGM sensors on my chest or abdomen have proven unreliable.

My favoured location is the outer part of upper arm, usually the right arm. I don’t have a lot of meat on me so I find inserting the sensor with the probe (filament) directed up towards shoulder rather than crook in elbow is best.

If you’re a side sleeper like me, location must be well out of the mattress contact point on upper arm.

i.e.: Approximately 30 degrees outward from the antecubital vein or fossa.

G5%20antecubital%20location

35

Just read, “What to Eat for Breakfast with Type 1 Diabetes”. Knew a lot, but also learned a lot particularly The Somogyi Effect which causes a drop on BG while sleeping which us important to almost all of us.

36

I have used the G5 for years without issues, so am somewhat perplexed by the complaint of false lows. I virtually never take aspirin, so cannot relate to that accuracy interference issue. I also realize that every T1D is different, so my observations may not apply to others. But here’s my 2 cents…

Generally, my G5 has been more reliable than my BG meter, and so I trust it more than any one individual BG meter reading.

Compression lows are the most common thing that I have seen that can cause my G5 to read low. I get compression lows either by sleeping on it, or resting my arm on it.

Water in the sensor can also cause wild readings. For me, this occurs when I take a shower and 1) I have not snapped the transmitter into the clips on both sides, or 2) have scratched the bottom of the transmitter such that water can seep inside.

I don’t think sensor age is an issue in this case. Loss of sensor sensitivity is related to duration of use, and NOT the time of day (aka, mornings). My G5 sensors would almost always last 14 days before the output would sag or become erratic. (My G6 sensors may last 7-12 days before they exhibit age issues.) But NOTE: the algorithm for day 1 expects the sensor to drift significantly, and thus restarting either the G5 or G6 sensor will give inaccurate readings for the first 2 days after the restart.

The BG level in the interstitial fluid significantly lags the BG level in blood. It also can be much lower due to muscles in the area burning fuel. So, if someone has a sharp dawn phenomenon, the G5 will read low due to the fact it is “a day late and a dollar short.” Also, if someone does sit-ups in the morning (or vomits!) the G5 will be low compared to a BG meter, but actually correct as the BG level where it is measuring it.

I am skeptical that calibrating the G5 too often is a big problem, per se. I think the real problem is that frequent calibrations typically occur during changes in BG level, and the normal lag in a CGM reading then causes the calibration to introduce error rather than reduce error. (If you really do have to calibrate during changing BG levels, fudge the number you enter to compensate for the CGM lag.) The other factor here is that BG meters have occasional wild test strips. Thus, I found it wise to take a 2nd BG meter reading if the first one disagreed significantly from the G5. Also, I found my G5 stayed accurate with only one calibration per day after day 2 (or after day 9 in the case of a restart). (My G6 never was accurate after a restart! So 10 days is the max for it.)

Hopes this helps…

3 Likes
37

SOMETIMES when I get out of the shower, I pop the xmitter off the G5 sensor and blot the terminals dry as well as the area around the sensor base,between the inner edge of the free overpatches from Dexcom, and the base itself. A Kleenex does a good job of blotting up the water. I also dry the bottom of the xmitter.

38

@rcarli

As other mentioned, the shower give me fake lows almost every single day. This is the only erratic behavior I’ve seen so far with both G4 and G5.

1 Like
39

This week has been probably the second time ever I have restarted a sensor and used it for more than a day (I have previously restarted and used it for a day or 2 just until I received my supplies…why they think it makes sense to make you wait until you are out of sensors to be able to order more I have no idea). It has been working fine for the last 10 days, but this is day 11 and it has been going crazy. Lots of false lows, and it will request calibration, jump up to what the level actually is, and then randomly fall down later.

I was really hoping I could get more time out of it, because for whatever reason my amount of supplies doesn’t match the warranty period and I am trying to get the G6 instead of ordering more G5 stuff. The warranty is up this week, so it should be this week or next for me to receive the G6.

40

I’ve had G5 sensors that lasted for 6 weeks and some for 7 days I find most sensors work best as they get older so I never change until they start to become erratic. And I always soak new sensors for 24 hours so generally avoid bad readings on the first day.