CGM Alarms and Alert Settings

What Alerts Are For

CGM alerts are meant to draw attention to glucose values that may need action. Most systems let users set a low threshold and a high threshold. A common starting point is a low alert near 70 mg/dL and a high alert somewhere around 180 to 250 mg/dL, but the right settings depend on age, hypoglycemia risk, pregnancy, insulin use, work, driving, and clinician guidance.

Urgent and Predictive Alerts

Urgent Low

Major systems include a fixed urgent low alert near 55 mg/dL. Dexcom describes Urgent Low Soon as a warning that glucose is predicted to reach 55 mg/dL within 20 minutes. Abbott describes an Urgent Low Glucose Alarm set at 55 mg/dL. These alerts are intentionally harder to miss.

Predictive and Rate Alerts

Some alerts trigger before glucose crosses the set limit. Guardian Connect can alert before a low when sensor glucose is predicted to go below the user's low limit. Dexcom also offers predictive low warnings and rate-of-change alerts. These can give useful warning time, but they may increase notifications if set too tightly.

Managing Alarm Fatigue

Alarm fatigue happens when frequent alarms make people less likely to respond. A practical alert plan usually starts broad, then tightens only after the user understands their patterns.

• Keep urgent low alerts active.
• Avoid setting high alerts so low that routine meals trigger constant alarms.
• Use repeat or snooze settings thoughtfully.
• Create different daytime and nighttime profiles when the app supports it.
• Review patterns with a clinician instead of reacting to every single spike.

Phone Modes and Sleep

Do-not-disturb behavior varies by platform. Dexcom G7 uses Critical Alerts on iOS for Urgent Low and Sensor Fail, and Quiet Modes can silence or vibrate alerts for limited periods. Libre apps allow Silent Mode for up to 6 hours, including urgent low sound, while visual and vibration notifications may still appear depending on phone settings. Guardian Connect warns that notifications must stay enabled and the app must run in the background for alerts to arrive.

Followers and Escalation

Remote followers can receive high and low notifications, but they need their own alert plan. Set expectations: who calls first, how long to wait, when to contact emergency help, and when not to comment. Escalation alerts are most useful when they support safety without turning every glucose change into a family crisis.