With the Dexcom G6 app version 1.4 and later, you can ask Siri to recite your Dexcom glucose readings out loud and display your graph directly on the lock screen. 

The Dexcom G6 app has to be downloaded and is different from the Dexcom G5 Mobile app. (Please note: The Dexcom G6 CGM System will not work with the Dexcom G5 Mobile app.) It is available for free from the Apple App or Google Play stores. The app is named “Dexcom G6”. Only one app can be used at a time on any particular device. Attempting to run or keep both apps on a device can result in either app not working properly. 

Getting Started and Setting Up the App