How do I fix a Dexcom G7 sensor that loses connection overnight with a Tandem t:slim X2?
Answer
A red X on a Tandem t:slim X2 usually means the pump lost valid Dexcom CGM data. This often happens when a newly placed sensor starts lifting or loses contact overnight.
Before you start: stop right away if…
- CGM and insulin pump issues can affect diabetes management. Follow your healthcare provider’s guidance and use backup glucose testing when CGM data is missing.
Follow these steps
Identify what failed overnight
Check the Tandem t:slim X2 and Dexcom app history for a red X, CGM communication loss, or sensor alert around the time the issue started.
You should see: You know whether the pump lost CGM data, the sensor reported an error, or both.
Inspect the current sensor site
Look at the Dexcom G7 adhesive and edges. Note any lifting, rubbing from clothing, or placement on a crease or bony area.
You should see: You can tell whether adhesion or placement is likely causing the overnight disconnect.
Choose a flatter upper-arm site next time
For the next sensor, use the back of the upper arm on a flatter spot with enough soft tissue, away from skin folds, waistbands, and areas you tend to lie on while sleeping.
You should see: The planned site looks flat, secure, and less likely to peel or press during sleep.
Re-check pump CGM status after replacement
After inserting and warming up a new sensor per Dexcom instructions, confirm the Tandem t:slim X2 is receiving Dexcom data again and the red X is gone.
You should see: The pump shows active CGM values, or a clearer pairing or sensor message remains if communication is still blocked.
Contact official support if data stays lost
If a new well-placed sensor still will not send data to the pump, use Dexcom and Tandem official support channels with the exact alert text and sensor start time.
You should see: You have the device messages and timing needed for manufacturer troubleshooting.
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Extra tips
What to look for: A red X on the Tandem t:slim X2, any Dexcom app alarm or error at night, and whether the sensor edge is lifting from the skin.
Before you change anything: Note the exact pump or Dexcom message you saw around 2 a.m. Check whether the current sensor adhesive is lifting before removing it. Follow your clinician and Dexcom or Tandem guidance for sensor replacement timing. Do not share account passwords or codes with unexpected callers.