Dexcom CGM: How Continuous Glucose Monitoring Works

A continuous glucose monitor, often called a CGM, is a small sensor you wear on your body that checks your blood sugar levels around the clock — no finger pricks required every time. The Dexcom app on your phone receives those readings every five minutes and displays them as a number and a trend arrow so you always know which direction your glucose is heading.

Understanding the trend arrows is one of the most important skills for CGM users. A straight arrow pointing right means your glucose is steady. An arrow pointing up or down means it is rising or falling slowly. Two arrows pointing up or down means it is moving fast — that is your cue to act right away, either by eating something or checking with your doctor about what steps to take.

The Dexcom app also lets you set alerts. You can choose a number that triggers a sound or vibration when your glucose goes too high or too low. Many people start with the default alert levels their doctor recommends and then adjust over time based on experience.

One of the best features of the Dexcom system is data sharing. You can invite family members, caregivers, or your doctor to follow your readings in real time on their own phones using the Dexcom Follow app. This gives your care team and loved ones peace of mind without you having to call anyone.

Your readings are also stored and can be shared with your doctor through Dexcom Clarity, a separate app and website that shows charts and patterns over days, weeks, and months. Bring a Clarity report to your next appointment so your doctor can see the full picture of how your glucose behaves throughout the day.

Always talk to your doctor before making any changes to your diabetes medication or treatment based on CGM readings. The device is a powerful tool, but your care team needs to be part of any major decisions.