Ordered my first CGM

Well I put in my first sensor last night. Seems to be going fairly smoothly. I know the inital day can sometimes be a bit off, so I’m not really that concerned with the discrepancies I’ve seen now.

I’m really unclear though whether I should pay attention to my monitor or my CGM. The rep I spoke to seemed to really be pushing the fact you can dose of the G5. However, this morning when I woke up my CGm was reading 7.1 mmol/ml where as my fingerstick was reading 4.9. It’s not a huge difference but for me, it actually makes a difference in my dosing enough that if I followed the 7.1 I would have gone low.

How often do people on G5 find they still do proper fingerstick tests, versus just using the CGM? I can already see the value in the trending of the data though. It’s really interesting to see exactly when it’s peaking.

I had a few instances over night where my low alarm went off, I woke up, checked my BGL via my glucometer and it was fine.

Donman, give it one more day and you will see that you will wake up with 0.1-0.2 difference. First day is usually the most unstable one. The longer you have the sensor, the better it gets. I see the best values on the third week actually. Try to calibrate at 7am and 7pm, that should give you good values throughout the day. I ONLY use G5 to dose and it works perfectly fine.

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In the US, the FDA advisory group has recommended the approval of dosing insulin based on the Dexcom. But the FDA has not approved it. This means that in the US, the Dexcom reps will still tell you to dose from your meter. That being said, any long-time CGM user will tell you that they have a pretty good idea about what sort of confidence you should have in your CGM. And you need to apply due diligence to the CGM readings, just like your meter. I can’t tell you how many times I have taken meter readings that were absurdly high or low and then upon carefully checking found that the reading was off. Apply the same caution to the CGM. As @BK1112 says, the sensor warmup in the first day or so can cause wonky readings. And when a sensor fails, again strange things. And for me, if I sleep on my sensor I will get pressure fails, usually a sudden dramatic drop to fire engine red lows. But upon checking with my meter, I am fine.


Well, as per everyone’s advice today’s readings have been far closer. It’s a weird experience for me still, after 17 years of diabetes being able to watch my glucose levels move. Although it’s probably not entirely reflective of the actual level in my blood it’s informative none the less.


10 days into my first Sensor and I found I had to change over today. I had been hoping to get at least 14, ideally closer to 20, days out of each sensor but perhaps this was just not to be on this occasion.

I’m interested how other people decide when they do actually need to replace the sensor?

The last two days I found to be extremely unpredictable. The CGM would constantly be making random jumps when my actual meter was stable. To the point that I just turned if off whilst I was out today as I constantly kept going from 5 mmol/ml down to 2.6 where I was getting low blood sugar warnings.

I’ve only been using the Dexcom since June. I’ve noticed that the readings start to get noise, jumping up and down every 5 minutes when I know I am stable. I would occaisonally get large jumps and alerts, but what most typically follows are actual dropouts with the dreaded “???.” And while the Dexcom would usually sync up after an hour or so the dropout would increase in frequency and I have loss for more than three hours. I’ll then change the sensor. I get more than a week out of sensor as long as there is no “operator error.”


I also had quite a few of the ??? icons for the past two days. They often went away within perhaps 30 minutes but the readings were always crazy following that.

What would you refer to as operator error?

Like ripping off the sensor on a door frame. I can be a bit clumsy.

I reliably get a 14-day average duration of my sensors. Some only last 10 days and others into the third week. When I see the ??? for extended periods, I will often just cut my losses and insert a new sensor. (I have good insurance help with financing these sensors and that influences the amount of time I will give a sensor to start behaving well again.) Like @Brian_BSC, I will often see the appearance of noise in the 5 minute updates. It will look like this series: 95, 99, 95, 95, 95, 99, 95, 99, 95.

One thing you might experiment with to increase sensor longevity is to stay well-hydrated. Sometimes I think my coffee habit dehydrates me and causes the “noise signature” as I listed above.

The three biggest signs that a sensor is dying for me are ???, erratic readings (more than 2-3 mmol/L off what my actual reading is), and as you experienced repeated false lows. Before changing out a sensor I always restart it once, and usually two or three times. Often a sensor that is not behaving will start behaving when it’s restarted. I get three weeks on average out of my sensors, sometimes significantly more and occasionally only two weeks.

@Terry4 Interesting comment on the ‘noise’. I actually never would have thought it much of an issue if I saw each 5 minute reading changing small amounts, like from 95 to 99 back to 95. But maybe I should keep an eye out for it.

I know if I do a fingerstick reading, chances are if I did one in 5 minutes on the same finger and nothing else had changed that it would be slightly different also.

While that amount of noise wobble doesn’t hurt the overall realtime precision, it tells me that my sensor is moving on to “middle age,” a sort of early notice of decline. I’m sorry I can’t view my data on shorter time slices down to three hours, except on Dex receiver.

Blood glucose doesn’t naturally and rapidly fluctuate for 5-10 mg/dL. It moves in a smoother fashion. It’s amazing how smooth a relatively flatline curve is when the sensor is working well.

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On another Tu site, someone suggested dealing with the ??? by tapping on the transmitter a few times, guessing that contact had been lost between sensor and transmitter (from bumping/sleeping on it, etc). Seems to work for me!

Well, I thought I’d share an update with my experiences with the CGM over the past few months.

Initially, I must say that I do love the CGM, it’s been a great asset to my diabetes control. I’ve managed to prevent going above my desired BGL range before it happens, prevent lows, and also watch some of the trends after eating and also whilst sleeping.

I generally found it to be quite accurate within the first week of use. Usually for me it was within .1-.4 mmol/ml of my finger stick readings.

The only exception to this is it always seemed to be at least 1 mmol/ml difference in the mornings. With the CGM often being lower. The only conclusion I could make here was that as I started to wake up, my blood sugar would rise a few mmol and the CGm just had not caught up yet.

I already had pretty tight control, so in some ways it was really just a personal confidence booster, as it showed me that my blood glucose actually stays pretty stable after eating. It also meant I could sleep without worrying about hypoglycaemia, as I could just set alarms. One of the most valuable experiences was wearing it during exercise. I go rock climbing 2-3 times a week, and usually bolus before this to prevent a post high BGL. I’ve never really known what my blood sugar looks like during the hour I’m climbing so it was great to see this.

I also found it really useful overnight as I would set an alarm for if I went over 6.5 mmol/ml and then could correct in that instance, rather than waking up with my BGL being like 8 or 9.

Having said all that, I have unfortunately decided to not continue funding the device. A number of things have lead to that, but predominately it was the fact the sensors simply did not seem to last anywhere near as long as I had hoped.

The three sensors I have currently used (I have one left that I will be waiting to use in a few weeks for the week off I have over Christmas), have only lasted around 10-12 days on average. Typically I get a week of very accurate readings, then it seemd almost on the 10 day mark the readings would start to become a bit less accurate and a few more days after this they would start randomly jumping around, giving me warnings when I wasn’t low and showing the dreaded ??? symbol.

Whilst 10-12 days might be fine if you have insurance that covers the sensors, having to fund this myself, I would be looking at something in the vicinity of $5000 a year.

I’m also going back to university in the middle of next year, and subsequently moving from full time to part time work. It’s been a great insight for me, and I’m sad I won’t be able to keep using it, but hopefully in the not too distant future some form of subsidies or insurance coverage comes into Australia for these awesome bits of tech.

It makes me sad that anyone using insulin should have to live without a CGM. But, then I lived for 25 years without it. It would be hard for me to give it up. Have you thought about cutting back to one sensor/month? Or one every other month? It might be nice to use it during periods you’d find it an advantage.

Good luck!

I’d start selling all of my earthly possessions on eBay before I’d have my daughter go without her Dexcom. Even with “great” (read “sucks less than others”) health insurance, the copays are killing me. But her quality of life (and hence my own) are so much better with her Dexcom that I will sell my very soul to the devil before I give up my daughter’s Dexcom.

And I agree with Terry4: No PWD should be expected to manage without a [Dexcom] CGM.

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I certainly have thought about only using it for specific instances, I doubt I’d go one a month as I don’t really see the advantage of just having one week every month on the CGM, unless something special is occurring during that week.

I can foresee me potentially buying some more sensors and a transmitter for when I next go travelling, as I said I’ve saved one sensor for the week off I have at Christmas where I won’t be following my normal schedule.

Whilst I found it awesome, and informative, I can’t say that it really improved my control greatly, it just made things easier. The thing is though, even if I started pinching all my pennies, once I stop my current job it would mean I’d actually have to cut back on things that I think would have a greater impact on my health and control, such as some of the foods I buy. I’d rather be ale to buy the types of food I currently do than have the CGM at this point in time.

I do get the feeling that I really have not properly understood the complete advantage of using it within the one or two months I’ve had it though, as I thought I’d have a much more stable 3 months of use but due to some

The problem I have with just using it occasionally though is you can’t just buy one sensor, so for when I next want to buy it I have pretty much to pay $900 straight up for four new sensors and a transmitter. I’m also unclear on how the transmitter works in regards to it’s three month life span. Is that three months of active use? For instance if I put a sensor in for a week, and then didn’t for another 6 months would that transmitter still work?

Unfortunately, the G5 transmitter starts a 90-day clock on the receiver with first use and you will lose the function of that transmitter when it times out. It’s set for 90 days + 22 day grace period. It won’t let you start another sensor if the transmitter has less than 7 days left of the 112 day period (90 + 22).

That makes intermittent use less economical. I use the G4 Share and it’s transmitter guarantee is 6 months and may last one year. There is no time clock working with it and battery life determines longevity.

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Yeah, I suspected as much. It’s a rather strange choice by Dexcom, I’m not really sure of the technical side behind it but you must assume if the transmitter isn’t actively being used it’s battery can’t be in use either so it’s unclear why it actually still ticks over unless it’s in use.

I more and more regret my decision to get the G5 vs the G4. It seems there are a number of things with the G5 that I can only explain through the view that Dexcom are after money. I’ve noticed this has recently changed in the last few weeks, which angers me, but when I got my Dexcom they would not sell the system to you without also selling you a receiver.

The result of this is I spent $500 on something I literally do not use. Why would I when I get the exact same information on my phone, which I have with me all the times!

One G4 sensor costs you $85?? Mine are $200 each!