The FreeStyle Libre system has two main parts: a reader and a disposable Sensor, which is worn on the back of the upper arm. The user wirelessly scans the Sensor with the compatible smartphone or reader to get glucose readings.  The Sensor pack is used with the Sensor applicator to prepare the Sensor for use. The Sensor is applied to the back of the upper arm with the aid of the Sensor applicator.  The small, disposable, 14-day Sensor is worn on the back of the upper arm and continuously measures glucose.  *Based on the Sensor being replaced once every 14 days and scanned once every 8 hours¹.

Reference

1. FreeStyle Libre flash glucose monitoring system User's Manual.