Tandem and g6 connection

ok so i have been diabetic for about a year now and i started using the tandem x2 back in February. i use control iq as i have frequent lows. i am also a very active person so i use exercise mode daily. im just curious as to if anyone else has this problem: when i do any kind of activity (dance, biking, running etc) i lose connection between my pump and my dexcom. i dont know if it’s because i move around a lot when im active or what. it pretty much defeats the whole purpose of having the exercise mode and it cause me to have unnecessary lows. i just want to know if anybody else has this problem.

Hi @synthea0 and welcome to the forum. I haven’t had that specific problem but here’s a thought - I admit it’s a longshot but you never know: the one thing that caused me to have regular connection issues was denim, and specifically and only if I had my sensor on my thigh and my infusion set on the opposite side of my body (left thigh/right abdomen for instance). Cotton? No problem. Polyester? Worked just fine. There was just something about denim that was problematic for me. Denim probably isn’t part of your workout wardrobe but you never know. And while I confess science was not my strong suit, maybe a different fabric is problematic for somebody else.
I use a shield and Simpatch to make sure my sensor stays in place - the patches are stretch fabric and I find they hold much better than the ones you can get from Dexcom. If your sensor is shifting as you work out, they could help. I find both in Amazon - PM me if you would like me to send a patch. They work best with the shield but you could try before you buy.

@synthea0 welcome to the forum and Type One Nation. I do not have a tandem pump but a lot of participants complain about the pump disconnecting from the CGM. My phone stays connected to my Dexcom unless I am very far (3 rooms or if I leave my phone and go outside) away. I have heard you need to keep the Tandem pump screen side away from your body for the strongest connection.

Why would the CGM connection cause low blood sugar? I totally see why activity can cause lows, I need to have zero insulin on board, and I need to cut basal by 50% or even 100% 40 minutes before activity in order to not crash. Anyway hope you are ok!

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Welcome @synthea0 to the JDRF TypeOneNation Community Forum!

I have been using Control IQ [CIQ] since the month it was released to the public - almost three years ago, and have not experienced the “Signal Loss” issue that you are seeing; and I’m quite active, for an octogenarian, and exercise regularly. CIQ has kept me well in-range [above 90% of the time on the standard scale] and thankfully has kept me from lows; I have my Dexcom “anticipated low warning” set at 80 daytime and 85 night time. I do have six Profiles programmed in my pump and activate the appropriate one depending on the anticipated activity level.

What I have learned while living actively with diabetes for over six decades is that “frequent lows” are more often the result of too much insulin delivered rather than by exercise - I’m not a medical professional, but rather an observer. May I offer two thoughts:

  1. Sensor Error” message is not when your pump looses connection with your CGM, but rather the result of either too fast a change in readings or a “pinched” sensor wire which can be the result of compression as the result of body position - example racing bike handlebars set way low.
  2. The “too much insulin” delivered before, during or several hours after exercise. The CIQ algorithm uses IOB from only bolus - you could have a Profile that would deliver you significantly less basal during at least 3-4 hours prior to beginning planned exercise even before you switch on “Exercise Mode”. Exercise mode attempts to keep us at 140 mg/dl and if I’m at 120 when I switch over I eat a medium duration snack, without insulin, to push up my BG to the 140 mark. For me, on evenings [ 8 - 9 PM] after a 20 - 30 mile bike ride my BGL will suddenly drop even after I’ve eaten a good supper - delayed action from exercise.

I wish you well - as you probably realize, each of us is different and what works for me may not fit you. And, the one constant I found about T1D is “Change” - what works today may not be true [for me] a month from now. Best advice is to stay aware of your body - but NEVER let diabetes rule your life - live fully!

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The pump has an aluminum shell, which blocks radio signals. The signal from the G6 sensor can enter the pump only through the glass front.

Be sure nothing is blocking the front of the pump while you are exercising, and that you don’t have anything metal covering the sensor. The pump and sensor communicate by Bluetooth, which is a very low-power protocol (so that they don’t drain the pump and sensor batteries too quickly). Thus, it does not take much shielding to block the proper communication between the two.


I was medtronic user for decades and i was originally taught that the abdomen was the only place to wear sensors. When i first started with the dexcom g6 i was constantly battling signal loss. I have since switched to the back of my arms and no longer have
nearly as much trouble. Any time you get any piece of your body or equipment covering the sensor you will lose connection. As previously stated by someone else I also cannot exercise with any insulin onboard and i start the exercise mode about 45 minutes prior to beginning activities. Hopefully this helps, it is a learning experience and a constantly changing scenario for many people.

This. I do have a Tandem pump and it absolutely disconnects randomly. The MAJOR thing is that you keep your phone on you. Let me know if your phone’s model is too “new” for the Dexcom app because there is a workaround. I put “new” in quotes because Dexcom is SUPER SLOW to connect to newer OS versions and phone models. It’s maddening.

Linda @Juggernautical , I use both a t-Slim pump - as my Primary Receiver, and a Galaxy S-10 as a pump Secondary Receiver for t;Connect functions and as Primary for Dexcom.

The phone when acting as Dexcom Receiver connects directly with the G6 transmitter. For the Tandem t:connect application the phone “pairs” with the pump. So technically, you could experience two different “signal loss” events when a Dexcom transmitter fails. If your Dexcom app is is displaying a glucose reading, with or without an arrow present you know the Dexcom is acting properly and when glucose readings do not appear on the pump the issue is with pump configuration or placement.

When glucose readings are missing, do not confuse “Signal Loss” with “Sensor Error” Although glucose readings are not displayed, they are entirely different; look at figures 25.16 and 25.15 on your Tandem User Guide. Causes and instructions for action are provided.

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oh my gosh, thank you all so much! someone mentioned the aluminum shell which i didnt even think about, someone else mentioned making sure that there is absolutely no insulin on board before exercise, amongst other things. i really appreciate your help!