A Dexcom is a small wearable device that continuously tracks your blood sugar levels throughout the day and night without fingerstick blood tests. Made by Dexcom, Inc., it falls into a category called continuous glucose monitors (CGMs) and is primarily used by people with diabetes. The sensor sits just under the skin and sends real-time glucose readings to your phone or smartwatch every five minutes, giving you a running picture of where your blood sugar is and where it’s heading.
How the Sensor Works
Unlike a traditional fingerstick meter that measures glucose from a drop of blood, a Dexcom sensor measures glucose in the fluid just beneath your skin, called interstitial fluid. A tiny, flexible filament sits in this fluid and continuously detects glucose levels, converting those readings into a number on your screen. Because interstitial fluid trails behind blood by a few minutes, your Dexcom reading can lag slightly behind what a fingerstick would show, especially when your blood sugar is rising or falling quickly. In steady conditions, the two readings are very close.
The sensor is inserted with an applicator that pushes the filament under the skin in about a second. Most people describe it as a brief pinch. Once placed, you wear it continuously and can shower, swim, and exercise with it on. The approved placement sites are the back of the upper arm for anyone age 2 and older, and the upper buttocks for children ages 2 to 6.
What You See on Your Phone
Every five minutes, the sensor sends a new glucose reading to the Dexcom app on your smartphone. You see a number (your current glucose) and a trend arrow showing the direction and speed of change. A flat arrow means stable. An arrow pointing steeply up or down means your glucose is moving fast. The app also displays a graph of your readings over the past several hours, so you can spot patterns after meals, exercise, or sleep.
One of the most valuable features is the alert system. You can set custom high and low thresholds, and the device will vibrate or sound an alarm when your glucose crosses those lines. There’s also a predictive alert called “Urgent Low Soon” that warns you when your reading is expected to drop to 55 mg/dL within the next 20 minutes. That early warning gives you time to eat or drink something before a dangerous low actually happens, which is especially important overnight when you wouldn’t otherwise notice the drop.
Sharing Data With Others
Dexcom includes a built-in sharing feature that lets up to 10 people, such as a spouse, parent, school nurse, or close friend, follow your glucose data in real time through a companion app called Dexcom Follow. Each follower can see your current reading, trend arrow, and graph on their own phone. Followers can also customize which notifications they receive, so a parent might opt into urgent low alerts while a friend only checks in occasionally. The person wearing the sensor controls who gets access and can revoke it at any time.
This feature is particularly popular among parents of young children with type 1 diabetes, since it allows them to monitor glucose levels during school or sleepovers without being physically present.
Current Models: G7 and the 15-Day System
Dexcom’s current flagship is the G7, which replaced the G6. The G7 is about 60% smaller than the G6 on the body, roughly the size of a coin at 1.1 by 0.9 by 0.2 inches. It also warms up in 30 minutes compared to the G6’s two-hour startup period, meaning you start getting readings much sooner after placing a new sensor. Each G7 sensor lasts 10 days, with an additional 12-hour grace period so you have some flexibility before you need to swap it.
Dexcom also offers a G7 15 Day system, which extends sensor wear to 15 days and reduces the number of sensor changes per month. Both versions connect directly to compatible Apple Watches (Series 6 and newer, running watchOS 10 or later), letting you check your glucose with a glance at your wrist without needing your phone nearby.
Who Uses a Dexcom
Dexcom CGMs are FDA-cleared for people with type 1 diabetes, type 2 diabetes, and gestational diabetes, ages 2 and up. They’re most common among people who take insulin, but they can also be useful for anyone whose doctor wants a more complete picture of their glucose patterns than occasional fingersticks provide.
Medicare covers a Dexcom CGM if you take insulin or have a history of problematic low blood sugar episodes, and if you or your caregiver have been trained to use the device as directed. Most private insurance plans also cover CGMs, though specific requirements vary. Without insurance, the out-of-pocket cost for sensors and transmitters can run several hundred dollars a month, so checking your coverage before starting is worthwhile.
What Daily Life Looks Like With One
In practice, wearing a Dexcom means you replace your sensor roughly every 10 to 15 days depending on the model, and otherwise just go about your routine. The adhesive patch holds the sensor in place through workouts, showers, and sleep. Some people find the adhesive irritates their skin over time, and Dexcom sells overpatches (as do third-party companies) that help keep the sensor secure and reduce irritation.
The real shift is informational. Instead of checking your glucose a few times a day, you have a continuous stream of data that reveals how specific foods, activities, stress, and sleep affect your levels. Many people find they make better decisions about eating and insulin dosing because they can see the impact in real time rather than guessing between fingersticks. The trend arrows alone change behavior: seeing a sharp upward arrow after a meal tells you something a single number an hour later never could.