Dexcom G6 User Manual page 26

If you're new to the Dexcom app, these screens go over your alarm/alerts.
After reading each screen, tap Next to move forward.
App: Setup
8
New users only:
Set your Low Alert. You'll get an alert if your glucose dips below the number you set. Default is 80 mg/dL.
Scroll to select your level.
Tap Save.
App: Setup
9
New users only:
Set your High Alert. You'll get an alert if your glucose rises above the number you set. Default is 200 mg/dL.
Scroll to select your level.
Tap Save.
App: Setup
LBL014003 Rev 001 Dexcom G6 User Guide 25