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Get familiar with how to use your Dexcom G5 Mobile CGM and Dexcom G6 CGM systems.

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Frequently Asked Questions


Can I still use the Dexcom Share feature with my t:slim X2 pump?
Yes. It is the Dexcom transmitter that talks to your compatible mobile device, not the pump. The Dexcom transmitter can be paired with one medical device and one non-medical device at the same time. (e.g. A transmitter can connect to your t:slim X2 Pump and a mobile device running the Dexcom Share app, or to a Dexcom receiver and a mobile device running the Dexcom Share app.)

When I pair my t:slim X2 insulin pump to CGM during an active sensor session (being viewed on a Dexcom receiver and/or phone), will I lose any data during the pump’s two-hour CGM warm up period?
No. Although the pump will appear as if it is starting the two-hour warmup period, within a few minutes you should start seeing readings on your t:slim X2 insulin pump. However, the Dexcom transmitter can only be paired with one medical device and one non-medical device at the same time. (e.g. A transmitter can connect to your t:slim X2 Pump and a mobile device running the Dexcom Share app, or to a Dexcom receiver and a mobile device running the Dexcom Share app.) If your Dexcom receiver isn’t properly disconnected prior to pairing your transmitter to your pump, you will see connection issues. Here’s the link to directions for properly disconnecting your receiver.

How do I change a transmitter or sensor when using the Tandem pump and the Dexcom Mobile App?
Learn more about how to change your transmitter or sensor when using both devices here.

Can I use a separate Dexcom receiver to view my data, in addition to the pump?
No. A single transmitter cannot be connected to both your insulin pump and a Dexcom receiver at the same time. Dexcom CGM transmitters can only be paired with one medical device (either a Dexcom receiver or t:slim X2™ insulin pump) and one consumer device (phone or tablet) at the same time.

I can’t get my t:slim X2 pump to stay connected to my Dexcom transmitter. What should I do?
If you are having difficulty pairing your Dexcom CGM with your t:slim X2 insulin pump, it may be because:

  • Your Dexcom transmitter is linked with your Dexcom receiver instead of your t:slim X2 pump. A single transmitter cannot be connected to your insulin pump and a Dexcom receiver at the same time.
  • Your phone with the Dexcom app is in a different room. Your Dexcom transmitter makes communication with the Dexcom app a priority; therefore, if you walk away from your phone while connected to both the Dexcom app and the t:slim X2 pump, the pump can become disconnected. If you wish to remain connected to both devices, please keep your phone near both devices to maintain the connection.
  • Your transmitter and pump can’t “see” each other. Your pump and transmitter should be within line-of-sight without any obstruction (including any body parts). Ensure that your pump and transmitter are on the same side of your body and that your pump screen is facing away from your body.
  • Your transmitter is outside of warranty. Your transmitter is in warranty for three months, but may last up to 112 days. If your transmitter has been in use longer than 90 days, Dexcom does not guarantee results, and you will need to get a new transmitter.

How do I disconnect my Dexcom transmitter from my Dexcom receiver?
Learn more about disconnecting your transmitter from your receiver here.

If a Dexcom G5 Mobile CGM sensor session in progress using my phone as the receiver, do I have to re-calibrate when I pair it with my t:slim X2 pump?
No. An additional calibration will not be required. All sensor session information, including the calibration information, is stored on the Dexcom transmitter, not on the devices connected to it. (This is different from the Dexcom G4 CGM, where each connected device had to be calibrated separately.)

Do I have to calibrate on both my phone and the pump?

  • For the Dexcom G6 CGM system: After entering the sensor code, you do not have to calibrate.
  • For the Dexcom G5 Mobile CGM system: You must enter two calibrations (aka “double blood drop” or DBD) after the two-hour warm-up period. Both of these calibrations should be on the same device. After the initial DBD, you will need to calibrate once every 12 hours for the full lifespan of the sensor session (seven days) and this can be done on either device.

What do I do if I have lost or forgotten my sensor code?
You must enter your first two sensor calibrations on the same device, either the pump or the phone. After that, calibrations can be performed from either device for the remaining life of that sensor. NOTE: It may take up to 15 minutes for the secondary device to register that a calibration was entered but it is not necessary to enter it on both devices.

How do I disconnect my CGM from my t:slim X2 pump?
Navigate to Options > My CGM > Stop Sensor.

NOTE: It will take up to 24 hours for the graph to disappear. A user may also reboot the pump and that will remove the graph and stop all communication with the transmitter immediately. During this 24 hour period, the pump will be searching for the transmitter and can partially or fully deplete the pump battery. It is important to carefully watch the battery during this time if you choose not to reboot your pump.

If the battery on my pump runs out, do I need to restart my sensor session or calibrate when the pump powers on again?
No. The sensor session information is stored on the Dexcom CGM transmitter. You may need to re-enter your transmitter ID on the pump, but you will not be asked to calibrate when you reset.

The battery on my t:slim X2 pump is significantly less with CGM. Is this expected?
Yes, this is expected. A single battery charge on a t:slim X2 pump can last for up to seven days during normal use without CGM and up to five days with CGM. The best thing you can do for battery health is to charge your pump each day for 10-15 minutes or until it is fully charged. Just like with a cell phone, the more often a display is turned on, the greater the impact on battery life. Things you can do to help minimize this on your pump include:

  • Clear alerts, alarms and reminders as soon as they appear
  • Set your Screen Timeout setting to 30 seconds (default). Options > My Pump > Pump Settings > Screen Options > Screen Timeout

Where can I upload and view my combined pump and CGM data?
Combined pump and CGM data can be viewed in our t:connect® application. Tandem pumps and Dexcom CGM systems can also be uploaded to Diasend and Tidepool.

Can you use the Dexcom G6 sensor beyond the recommended 10 days?
No. Unlike with a Dexcom G5 Mobile sensor, a Dexcom G6 sensor has a mandatory shutoff at 10 days, after which it cannot be used.

Can I start a CGM session immediately after my pump is out of storage mode?
No. Please wait at least 20 minutes from the time that you turn off storage mode before starting a CGM session. If you do not wait 20 minutes, a CGM error may occur. If this occurs, please call Tandem Diabetes Care® Technical Support at (877) 801-6901.



Still have questions?

24/7 live support is here. Read the list to contact the appropriate support specialist to get the answers you need.


Dexcom Technical Support

  • Insertion issues
  • Site-related problems (discomfort, bleeding, adhesive)
  • Damaged CGM component

Contact Dexcom


Tandem Technical Support

  • Signal issues
  • Error messages
  • Other events communicated by your t:slim X2 insulin pump

Contact Tandem