Dexcom G5 User Manual page 194

Warning
Disconnect headphones from your smart device when not in use.
Do:
Why: If headphones are connected while not being used, you won't hear
an Alarm or Alert.
Consequences: Missing severe low or high glucose Alarm or Alerts.
Precaution
Never prevent communication between transmitter and display
Don't:
devices.
Keep smart device and receiver within 20 feet of transmitter and away
Do:
from obstructions.
Why: If your transmitter and display device(s) are more than 20 feet apart
or are separated by an obstruction, they might not communicate.
Types of obstruction differ and not all types have been tested. Obstructions
can include water, walls, metal, etc.
Water (for example, when swimming, surfing, bathing, etc.) can severely
limit communication range.
Consequences: Missing severe low or high glucose Alarm or Alerts.
Precaution
Set smart device and receiver settings separately.
Do:
Why: Settings are specific to each display device and don't carry over to
other devices. If you set up one device and then use another, you won't get
an Alarm or Alert.
Consequences: Missing severe low or high glucose Alarm or Alerts.
Dexcom G5 Mobile System User Guide
Sensor Glucose Alarm and Alerts
194