How do I start and stop a Dexcom G6 CGM sensor session?

View the following tutorial to learn how to start and end a CGM session with Dexcom G6 CGM:

Tutorial: Starting and Ending a CGM Sensor Session >

Download a PDF of this process here >

To start a CGM session, follow the steps below. If you want to continue an existing sensor session after receiving a replacement pump, or after starting a sensor session on the Dexcom mobile app, these same steps apply. If you just ended a sensor session, wait 10-15 minutes before starting a new sensor session.

1. From the Home Screen, tap OPTIONS.

2. Tap My CGM.

3. Make sure the Dexcom transmitter is linked with your t:slim X2 pump.



4a. If your screen displays STOP SENSOR, this means a sensor session is already in progress. If this is because your pump is still connected with your old sensor, you may press STOP SENSOR to end the current session, then START SENSOR to begin your new session.


✓ Once you start a sensor session, the START SENSOR option is replaced with STOP SENSOR.

The following prompt displays prompting you to either enter the sensor code, or to skip this step. If you choose to enter the sensor code, you will not be prompted to calibrate for the duration of the sensor session. For information about Dexcom G6 CGM sensor codes, refer to the manufacturer’s website for applicable user guides.



If you don't have a code, you can tap skip. If you don't enter a code into either the t:slim X2 or a Mobile App, you will be prompted to calibrate your sensor every 24 hours.

5. Tap mceclip6.png to confirm.


✓ The “SENSOR STARTED” screen will appear to let you know your sensor startup has begun.

✓ Your t:slim X2 will return to the CGM Home Screen with the 3 hour trend graph displayed.


6. Check your t:slim X2 Pump CGM Home Screen 10 minutes after starting your sensor session to make sure your pump and transmitter are communicating. The antenna symbol should be to the right of the battery indicator and should be white.



Out of range

If you see the out of range symbol below the insulin level indicator, and the antenna symbol is grayed out, follow these troubleshooting tips:


  • Make sure your t:slim X2 Pump and transmitter are within 20 feet of each other without obstruction. Re-check in 10 minutes to see if the out of range symbol is still active.
  • If the pump and transmitter are still not communicating, check the CGM Info screen to make sure the correct transmitter ID is entered. 
  • If the correct transmitter ID is entered and the pump and transmitter are still not communicating, contact Tandem Diabetes Care Customer Technical Support at (877) 801-6901.

Sensor session ended (clock icon)

If you see the sensor session ended (clock icon) symbol below the insulin level indicator, follow these troubleshooting tips:


  1. Make sure the Sensor Code was entered correctly. You can check to see what code was entered by navigating to Options > History > CGM History > Sessions and Calibrations.mceclip11.png

Sensor startup period

As an example, the Dexcom G6 Sensor needs a 2-hour startup period to adjust to being under your skin. You will not get sensor glucose readings or alerts until the 2-hour startup period ends and you complete your first calibrations. For information about Dexcom G6 CGM sensor startup periods, refer to the manufacturer’s website for applicable user guides.

During the startup period, the CGM Home Screen on your t:slim X2 Pump shows a 2-hour countdown symbol in the upper right portion of the screen. The countdown symbol fills in over time to show that you are getting closer to the end of the startup period.

NOTE: End Current Session Before Starting a New Session

Once your sensor session has completed, you must end the current session before you can start a new session.


For example, if you started your sensor session 20 minutes ago, you would see this countdown symbol on the CGM Home Screen.

If you started your sensor session 90 minutes ago, you would see this countdown symbol on the CGM Home Screen.

At the end of the 2-hour startup period, if you have not entered the sensor code, then you will be prompted to enter 2 calibration values. 2 blood drops will appear in the place where the countdown symbol was. If you entered a sensor code, the countdown symbol will be replaced with the current CGM reading.

If you did not enter a sensor code, then follow the instructions in the next section to calibrate your sensor. Skip the calibration instructions if you entered a sensor code.

Important note about Dexcom support:

Dexcom and Tandem have agreed which system issues are best handled by each company, including which company is responsible for reporting those events to the appropriate regulatory authority. To help ensure that the required reporting takes place in a timely fashion, customers may need to contact Dexcom for some issues and Tandem for others.

Tandem handles issues such as loss of connection (on pump only) and the invalid transmitter (Alert 29) on pump only.

For all other CGM issues, including would not accept calibration, the sensor failure during the 2-hour warmup, “no restarts” alert or physical problems with your sensor or transmitter, such as bleeding, bruising, skin reaction, adhesive issues, applicator issues, or broken wires, you should contact Dexcom using one of the options at


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