Start new sensor before bed

Being new to CGM (using a Dexcom G6) was wondering everyone’s thoughts about starting a new sensor session before going to sleep.

I use Basaglar 10U Qpm along with Humalog and have not experienced any overnight lows.

Seems like a good consistent time to start the sessions, but I defer to the experts out there


Welcome to the CGM community. I am always so thrilled to see someone give it try! I will say, it is my favorite tool in my very big diabetes toolbox!
And this like so many things relating to diabetes, is a personal choice.
So many things were said to never do before bed but many have gone by the wayside. Like no infusion set changes before bed but with a CGM, I never worry about (and using metal infusion sets-no kinking). Or never ever before bed-CGM again, no worries. Or no major drinking before bed-CGM again, no worries.
I think the only thing that might be a problem for some is compression issues, which I have never had, but many people have. Mine is set for 2:30 in the afternoon. That way I don’t get the end of session warnings while sleeping. And I find that I just insert it even at work when I’m on a break and it fires up after 2 hours. This is really whatever works for you!
I hope you find the information you will get from it very helpful.


Thanks for the reply and welcome ! I don’t have compression issues overnight, also with the G6 seems to vary the day and (possibly the time) for changes since it’s on a 10 day schedule. I’m set to expire midday tomorrow (inconvenient time to swap) so I thought I’d end early and place tonight.

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Like Sally noted, an afternoon or convenient time is the best for me too. I like to know it is reading correctly before going to bed. I check my BG to compare to the Dexcom before going to bed. I do have low BGs and count on my Dexcom to tell my Tandem pump to suspend delivery. I no longer feel moderately low BGs - feel them once they are at 30 mg/dl or lower. It all depends on your risks and comfort level. I wear sandals all the time and many diabetics are told not to but, I have no neuropathy or circulatory issues and love my summer sandals :slight_smile: Be safe and use tailor the technology to your needs.


I don’t like starting sensors before bed. In fact, I “soak” my sensors for 1 day prior to installing the transmitter, so that I get accurate first-day numbers.

I also won’t start a sensor too early in the morning because then I’ll run up against the “sensor expires now” problem earlier than I’d like 7 days hence. I don’t want to be forced to get up early to deal with an expired sensor. So starting after about 8 AM works well for me.

I often experience faulty readings the first 24 hours following insertion of new sensor. For this reason, I don’t like to start a new sensor at night because chances are I’ll be woken by false alarms.


It’s the same for me. As long as I ‘soak’ the sensor for 12 hours or so before starting the session, the initial readings are accurate. I can start the session anytime I like, including bedtime.

Before I did this the numbers were inaccurate for the first 12-24 hours. When I started at bedtime I invariably had false alarms during the night. Sometimes I had to shut down my phone so I could get some sleep!


That is one of the nice things about G6 is, if needed, you can start it at bed time and not worry about needing to calibrate in the middle of the night. I have done it a few times and it has worked out just fine.

For me G6 is much more accurate Day One than G5.

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Most G6 sensors are good for us. But not all. We sometimes get a bad one. Bad for who knows what reason and frankly I don’t care. User error, bad site selection, pressed the button wrong, manufacture error, shipping damage, I don’t care.

Until a meter check confirms a good sensor then I am not going to trust it.

Sometimes we do start a sensor at night.
Which means I will set a few alarms on my phone and get up during the night and do a few meter checks.
With the Basal-IQ, we run MUCH lower at night then we previously did. It is not uncommon to be mostly straight and level (with small waves) about at 80 throughout the night as the Basal-IQ kicks in and out and maintains the BG. Obviously, this requires a good data signal.
Point being there is much less room for error as opposed to when we might be running 140~160 at nighttime specifically to allow for a very wide range of BG movement.

So, I prefer not to start a sensor at night.

If it seems the most practical based on what else is going on (life still happens) then I will wake up a few times during the night to check that everything is OK.


I like doing them when I am sleeping, then I just wake up and calibrate. But I seem to be doing them at about 10-11 fridays now, which is ok but not great because I don’t want 2 hrs of no readings after I eat and I am up doing stuff.

I pretty much have to do nothing for 2-3hrs after eating or I will crash frequently. The first day is usually not great but I have very off numbers anyway.

I used to wear the Dexcom G5 and I am now on the Libre 14-day. I’d hardly consider myself an expert. But I will say that I’ve always started my new sensors at night, simply for the start-up timing. I’ve never really worried about my overnight numbers because I eat a late dinner and always wind up rising overnight. Even with increased basals I typically wake up higher than I’d like to be. So in knowing my patterns with rises in BG, I’ve always done nighttime sensor changes.

Thanks everyone for your thoughts and replies, I did start a new sensor last night and it seems to running as expected. I covered myself with fingersticks (as I do the first 24 hrs).

Again THANKS !

I would just chime in that a few times with a new G6 sensor I’ve had false lows in the first 6 or 12 hours. My blood sugar might be dropping to say 75, but my G6 will show that I’m at 54 and dropping rapidly. It doesn’t seem to happen after 12 hours of using a sensor, so maybe I should start “soaking”
For what it’s worth, I’ve never had a false high, only false lows with the g6 and only early in the life of the sensor.
Of course, if the g6 is accurate from the get go for you then it is one of the great things about it that you won’t have to wake up and do a calibration.
(Before the G6, I thought that calibrations were no big deal and I didn’t mind doing them. I thought “no calibration” CGMs were unnecessary but now that I’m used to the G6 I have to say that not having to calibrate is an unexpected luxury.)


Hi Dave,
What does “soak” mean in this context?

Means inserting a new (second) sensor before the current sensor has expired, usually about 24 hours or so in advance. That allows for the new sensor wire to “soak” in your interstitial fluid for a period of time which helps stabilize and give more accurate readings as soon as the new sensor goes active. You leave your old sensor going until it expires and then move the transmitter from the expired sensor to your new sensor that has been “soaking”.

I have a ghost writer!

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Ya, when I didn’t see you answer promptly, thought I would just pitch in as Sally was new to the community and wanted to get some info to her right away. Feel free to modify my response.

I have a question for all of you who soak - can you get the sensor wet the way we do with the transmitter attached?


I don’t know as I take an 8 AM shower every morning and soak sensor day before it needs replacement so insert sensor after shower and then transition from old sensor to new sensor before 8 AM shower next day. For the 24 hour period I leave new sensor fully exposed and never gives me any problems, however have not taken shower or gone swimming with exposed sensor. There is nothing to really get damaged by water that I can see, but since it is an electrical contact, who knows. If mine got wet, I would certainly dry it with hair dryer before inserting transmitter.

I put mine in to soak the night before, preferably Saturday night.
I have showered with it open and not had any problems.