Tslim drops bluetooth to transmitter and phone

Hi there, hoping for a little help. I have been using the tslim (control IQ) and a G6 together for about 2-3 weeks. I have a huge problem with the tslim dropping the connection to the G6. This happens frequently at night and lasts for several hours. Because this disables the Control IQ, I have had some severe hypoglycemia. It will always eventually reconnect, but in the meantime I am left with very low BS and a lost night of sleep.

Has this happened to you ? Is there a solution ?

My pump also has trouble maintaining a connection to the phone app. (iPhone Xs). This is only a problem when I want to rely on tConnect’s alarms, still it makes me question if my pump has a bad bluetooth controller.

I have spoken to Tandem, but their tech support people are not trained to do real troubleshooting and barely know how their product works.

Any help is much appreciated.

Check info from Tandem site.
My understanding is that the pump is like the receiver, which communicates different from bluetooth. But the link below says the phone app/bluetooth is looked for first, and once linked, then will try link to pump/receiver.
Do you have dexcom app on iPhone, or do you just use T;connect app or pump screen to view cgm trend? The X2 pump uses Bluetooth connection to get T:connect updated, after the other connections are made.

If you have a dexcom G6 receiver, it must be off.

Try turning your pump around, so the screen is facing out rather than into you. The Bluetooth antenna is behind the screen, and Bluetooth does NOT travel through water (or people made up nearly entirely of water) well.

It also helps to try and ensure a clear line of sight between pump and sensor. As in, keep them on the same side of the body and try not to put your sensor anywhere you might sleep on. Since I’m a back/side-sleeper, I keep the front of me open for Dexcom sites, and use the sides and back for infusion sites.

I can actually get away with the screen facing me during the day, but I can’t sleep that way. I can’t have the pump facing my waterbed, or I get no signal. I just set the pump on the bed, though, and no trouble.



I concur completely with @Robyn_H related to communication that has to go through water … whether it is a waterbed or your body.

When I wore my sensor on my abdomen, I found that reading a book would cause my sensor to drop out. Why? My forearms were laying across my abdomen. The end result … no signal, because my sensor (which is transmitting the signal) was enclosed in a “meat sandwich” between my belly and my forearm. I have better luck wearing the sensor on the back of the arm. However, even then, I occasionally lose signal while reading. Why? I wear my pump on my belt … and sometimes my arms are low enough when seated that the pump (AKA the receiver) is blocked.

Depending on where your sensor is relative to your pump, when you are sleeping, it’s fairly easy to roll over so that the radio signal would have to go through a lot of you to get to your pump

Best of luck!


Independent from any pump whatsoever, I loose G6 comm pretty frequently.

BT is a weak signal that is easily disrupted by many, many things.

We have dropped into a cold spell this week in MN and my use of blankets has been blocking signal overnight. Note: this is made a bit worse by the fact that I have been getting overnight lows, which then make me colder, which then cause me to turn on the electric blanket, which then causes more interference with the signal.

Wow, thanks for all the suggestions. I do not use a Dexcom receiver, but do use both the Dexcom App and the tConnect App. I typically wear my dexcom on the underside of my bicepts, leaving my belly for the infusion sets. I keep the tslim in a Flipbelt. I do face the pump outward, all the time.

However, as I toss and turn at night, I might position my body on top of the tslim or perhaps sleep on my side trapping the Dexcom underneath and with my body in between the two devices…

I have worn an OmniPod for the past 10 years, mostly on my belly, so that tissue is pretty well worn, thus my decision to use the Dexcom on my arms. Getting used to sleeping with a tube is a bit challenging…

I suppose I can put my Dexcom back on my belly and shift the tslim in the belt to the same side, that might minimize the flesh that the bluetooth has to go through.

Where do you recommend wearing the pump and the transmitter so as not to run into these troubles ?

Thanks a million for your help.

I tried using the t-slim pump for my insulin delivery as well as my Dexcom data receiver, but the short range of reception irritated the heck out of me. So often losing connection! I get you have to use the pump for control IQ, but why in the world is it so darned short ranged?? Instead I’ve chosen to use the receiver that came with the Dexcom. Good to 20 odd feet from the transmitter. Much easier for me, and I prefer it to control IQ. I check my receiver compulsively all day and do well enough (A1C 5.6-5.9) this way. We need to push Tandem to improve the reception distance of their pump, I think.

So you mean you are using. both the G6 receiver AND X2 ?

The X2 pump is a receiver, and does not use bluetooth to connect transmitter. The transmitter can only have one connection this way, X2 OR G6 receiver. A 2nd connection to transmitter can be to phone via Bluetooth.

If you want the X2 and control IQ, you need to stop using receiver.

Do you use phone with T:connect app?

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Because that’s exactly what Bluetooth is. Bluetooth uses a very weak radio signal that can only travel about 30 feet and is easily blocked, which is precisely why it’s available for open use and not a limited use/licensed frequency. It’s available to use freely for these short-distance communications precisely because there is little practical use for it otherwise and it’s too weak to wreak much damage if someone tries to employ it inappropriately.

The problem isn’t with the pump being more weak or defective. It works exactly like your cell phone and receiver do to communicate with the transmitter (sorry @MM1, but all the talking is done via Bluetooth, even to pump and receiver). The problem is with the close proximity and all the possible interference the signal can face trying to get from one place mounted on your body to another place mounted on your body. There’s a lot of chance for something to disrupt the signal. This is one of those problems that largely goes away once the pump trains you how to place things happily. Moving the pump away from our lumps, bumps, curves, and miscellaneous interfering appendages will actually improve connection. The pump trained me to put it on the bed next to me at night, rather than attaching it to me, or else I get dropped communication alarms. I don’t know why, but I’ve never seen much of a problem with this during the day.

The one thing Tandem could do better is rearrange some internal components so the Bluetooth antenna isn’t behind the screen. But I think that’s one of those, no win situation things. My perfect wear placement requires the screen to be facing me, otherwise I would look like Ironman all the time with a brightly lit chest bulge. But that’s just how I like it, I’m sure it’s a 50/50 split on directional preference.

@MM1 had a great point about not being able to use both the pump and receiver, though The G6 can connect to one primary medical device (pump OR receiver) and one secondary device (smartphone or standalone watch mostly). If you’re trying to use BOTH the receiver and the pump, they’re going to fight one another and the information will only go to the strongest connection.

Hi MM1!
I tried using my t-slim pump to connect with my G6 receiver for awhile. I didn’t like it though, due to how close it has to be to where my sensor/transmitter is on my body to stay connected and show me readings. So I turned off the Dexcom function on my pump and went back to the receiver that came with my G6 kit. I’m a lot happier that way, though you’re right, I can’t use Dexcom Control IQ this way. I read enough about people disliking aspects of that system to decide I wanted to stick with what I’ve been doing that’s working ok for me.

I’m guessing it’s just me with such preferences. I think if I were either younger, or older and in hospital/nursing home care, Control IQ would rock and I’d turn it on. But for now I like the lower A1C that tight attention to stats gives me. I have Addison’s disease and no thyroid gland left as well as T1, and they all mess with each other, so getting on top of bg swings ASAP helps me stay functional, mostly.

I have the t;slim with control IQ also. I have an I-phone 8 with the Dexcom G6 app on it. I wear a t-shirt with a pocket inside out to bed and put the t:slim in the pocket with the screen facing away from my body. The t-shirt pocket ends up being on my right side and my G6 transmitter is on my right side also. My phone is plugged in on my bedside table on my left. I use cotton sheets and cotton blankets. No electric blankets nor bed warmers. I have never had a disconnect during the night, but I do get disconnects from my cell phone at times. I wear my cell phone on my left hip and with the G6 on my right side, if there is metal/ iron near my G6 transmitter either on the left side of my body or behind me, as if I sit in a chair or couch that has metal/iron springs in it, I do get disconnects for 15 to 20 minutes or so. I have noticed that blue tooth seems to work better if wifi is on rather than off. Therefore I believe wifi has some effect on blue tooth operation. I also believe that any nearby radio frequency transmissions/receptions, iron or magnetic metal, or magnets or magnetic lines of force or any other form of non-ionizing radiation affects the wifi and therefore will also affect the blue tooth. If I am incorrect or if there is proof of concept other than my belief please inform me.

If the t:slim x2 & the Dexcom receiver don’t use bluetooth to connect, then what do they use? You appear to be saying that the Dexcom G6 transmits using two different protocols.

That seems unlikely to me if for no other reason than it increases the product cost. Why on earth would Dexcom do that? What benefits would it provide to justify the extra cost & complexity?

I’ve tried a (brief) search for G6 transmitter specs and all I’ve been able to find is a reference to 2.4 GHz Bluetooth Low Energy (BLE). What am I missing?

In a call with Tandem support, they stated there was a different way receiver or pump connected, I didn’t ask for details.

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I think the dexcom on the backs of ur arms is a better choice. I sometimes lose connection to my phone but never my pump to dex. Except when I have a bad sensor.
Also there are stickers you can buy. Yes stickers.

They were old time signal boosters from flip phone days but you can still get them.

And I use one on my pump and it really does increase the ability to receive signals

You can find em on Amazon or eBay etc. search for cell phone boost stickers. I bet you will find them for about a dollar each. They typically last for ever if you put it under the phone clip so it doesn’t get rubbed off. Otherwise maybe it will last a month.

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@irrational_John @MM1

I PROMISE, all the communications are done via Bluetooth (BLE).

Page 326 of the Dexcom G6 user manual specifically states that it will not accept communications any other way:

The G6 System is designed to transmit data between the transmitter and designated
display devices in accordance to the industry standard BLE protocols. It will not accept
radio frequency (RF) communications using any other protocol, including Bluetooth
classic communication protocols.

Page 184 of the X2 user manual:

Bluetooth Low Energy technology is a type of wireless communication used in cell phones and many other devices. Your t:slim X2 pump and a CGM transmitter wirelessly pair together with other devices using Bluetooth wireless technology communication. This allows the pump and transmitter paired devices to communicate securely and only with each other.

Either the Tandem rep was confused, inadequately conveyed something, or you misunderstood something.

I assume what was meant is that the X2 accrually has TWO Bluetooth radios/antennae. When they rolled our Control-IQ (and also updated Basal-IQ at the same time), they added the Bluetooth toggle button to the interface. There was a lot of communication at the time, and again later when they rolled out the T:connect app, because there was confusion about the purpose of the button. Tandem kept assuring people that the toggle was only for future mobile communications and would have no affect on Dexcom Bluetooth communications.

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My signal is stronger with my iphone than with my X2. Often when my X2 has the no signal icon, my phone is still OK. I find that without fail, my pump signal drops while I’m out and about walking for exercise - I don’t know why. It doesn’t happen for the entire walk, the readings come back sporadically. The distance between my pump and my sensor is at most 2 feet away (more like 1 feet) and my pump is facing outwards. I think the pump can us some improvement with the bluetooth signal as it’s not the best.

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Thanks. I did a little more research and found out the Dexcom transmitter does not transmit through my body well. So that if roll on my side and ‘hide’ the transmitter between my body and the bed, my receiver goes blank until I move. I have also noticed that the more “electronics” about me, the more often I get disconnects.