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.
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 with the connection between your Dexcom transmitter and t:slim X2 pump, questions about calibration, the “---” display, and sensor failures after the 2-hour warmup period.
For all other CGM issues, including 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 dexcom.com/contact.