When the sensor and app are in range, the FreeStyle Libre 2 system automatically communicates to give you Low and High Glucose Alarms if they are turned on. The Low Glucose Alarm notifies you if your glucose drops below the level you set. The alarm does not include your glucose reading, so you need to scan your sensor to check your glucose. The High Glucose Alarm notifies you if your glucose rises above the level you set. The alarm does not include your glucose reading, so you need to scan your sensor to check your glucose reading.