Dexcom makes continuous glucose monitors (CGMs) that track your blood sugar levels around the clock. These small, wearable sensors are primarily used for managing diabetes in people age 2 and older, giving you a real-time glucose reading every five minutes without fingerstick blood tests. Dexcom also offers an over-the-counter option for adults who don’t use insulin but want to understand how their blood sugar responds to food, exercise, and stress.
How a Dexcom Sensor Works
A Dexcom CGM consists of a tiny flexible wire inserted just beneath the skin and a small transmitter attached on top. The wire measures glucose levels in the fluid between your cells, and the transmitter converts those measurements into a glucose reading that gets sent to your phone or a compatible receiver every five minutes. The system is factory-calibrated, so you don’t need to prick your finger to set it up or keep it accurate.
The sensor sticks to your skin with an adhesive patch. For the G7, the FDA-cleared placement site is the back of the upper arm for anyone age 2 and older, with the upper buttocks as an additional option for children ages 2 to 6. Once applied, you wear it continuously, including during showers, exercise, and sleep. The device is not cleared for use during pregnancy, dialysis, or critical illness.
Who Dexcom Is Designed For
Dexcom’s prescription CGMs are cleared for anyone with diabetes age 2 and older, covering both type 1 and type 2 diabetes. The G6 and G7 systems are specifically intended to replace fingerstick testing for making treatment decisions, meaning you can adjust insulin doses based on what the sensor reads without confirming with a finger prick. That’s a meaningful distinction from earlier CGM technology, which required fingerstick confirmation before acting on the data.
People with type 2 diabetes who don’t use insulin also benefit. In a study of 909 CGM users with type 2 diabetes not on insulin, those using real-time CGMs like Dexcom reduced their A1c by an average of 1.01 percentage points. More than half achieved an A1c below 7% during follow-up. The continuous feedback loop helps people see exactly which meals spike their blood sugar and how physical activity brings it down, turning abstract lab numbers into daily, visible patterns.
The Over-the-Counter Option: Dexcom Stelo
Dexcom Stelo is a separate product available without a prescription, designed for adults 18 and older who do not take insulin. Each Stelo sensor lasts up to 15 days. Unlike the prescription models, Stelo displays glucose values on a narrower range (70 to 250 mg/dL) and does not send urgent glucose alerts. Instead, it provides an “Insights” feature that shows your time in range and offers suggestions for improvement.
Stelo updates the glucose value on screen every 15 minutes rather than every 5, and the displayed reading may be up to 15 minutes old. It’s built more as a wellness and awareness tool than a medical decision-making device. If you’re curious about how your body handles carbohydrates, or you have prediabetes and want real data to guide lifestyle changes, Stelo fills that role without requiring a doctor’s visit.
Dexcom G6 vs. G7: Key Differences
The G7 is the newer model and improves on the G6 in several practical ways. The most noticeable change is size: the G7’s on-body sensor is 60% smaller, measuring roughly 1.1 by 0.9 by 0.2 inches compared to the G6’s 1.8 by 1.2 by 0.6 inches. Warm-up time dropped from 2 hours on the G6 to 30 minutes on the G7, which means less downtime when you swap sensors.
Both sensors last 10 days, though the G7 adds a 12-hour grace period at the end so you don’t lose coverage if you can’t change it right away. A newer version, the Dexcom G7 15 Day, extends wear time to 15 days with the same grace period, though it’s currently cleared only for adults 18 and older.
Accuracy You Can Rely On
CGM accuracy is measured by something called MARD, which represents the average difference between what the sensor reads and an actual blood glucose measurement. Lower is better. The current G7 has a MARD of 8.2%, and the upcoming 15-day G7 improves slightly to 8%. For context, more than 80% of individual sensors tested in clinical evaluation had a MARD below 10%, meaning the vast majority of readings are close to a lab-quality blood draw.
Accuracy holds across different glucose ranges. In the low blood sugar zone (54 to 69 mg/dL), MARD was 8.2%. In the high zone (181 to 250 mg/dL), it was 7.8%. That consistency matters because accurate readings in the low range can prevent dangerous hypoglycemia, while accuracy in the high range helps you dose insulin correctly after meals.
Alerts That Warn You Before Problems Hit
One of the most valuable features of Dexcom’s prescription sensors is the alert system. You can set custom high and low glucose thresholds, and the device will notify you with a sound or vibration when your levels cross those lines. More importantly, the G7 includes a predictive alert that estimates whether your glucose will drop to a dangerous level within the next 10 to 30 minutes. This “Urgent Low Soon” warning gives you time to eat something and prevent a hypoglycemic episode before it happens, rather than reacting after the fact.
You can customize which alerts are active and adjust the thresholds. Some people silence the high alerts overnight and keep only the low alerts active. Others want every notification. That flexibility lets you balance safety with avoiding alert fatigue.
Integration With Insulin Pumps
Dexcom sensors connect directly to automated insulin delivery (AID) systems, creating a closed loop where your pump adjusts insulin doses based on real-time glucose data. The Omnipod 5 system communicates directly with the Dexcom G6 transmitter to automatically increase or decrease insulin delivery. The Tandem t:slim X2 with Control-IQ also integrates with Dexcom G6, predicting glucose levels 30 minutes ahead and adjusting basal rates accordingly.
Other compatible systems include CamAPS FX (used with Dana or YpsoPump insulin pumps) and the upcoming Tidepool Loop. For people with type 1 diabetes, this integration is transformative. Instead of manually calculating doses and reacting to glucose swings, the pump and sensor work together to keep blood sugar in range with far less effort. Many users report better overnight control especially, since the system adjusts insulin while they sleep.
What Daily Life With Dexcom Looks Like
Applying a new sensor takes about a minute. You peel the backing off the adhesive, press the applicator against your arm, and push a button. A spring-loaded mechanism inserts the thin wire under your skin. Most people describe the sensation as a brief pinch, less painful than a typical fingerstick. After the 30-minute warm-up (for the G7), readings start flowing to your phone automatically.
Throughout the day, you can glance at your phone to see your current glucose level along with a trend arrow showing whether it’s rising, falling, or stable. That trend arrow is often more useful than the number itself. A reading of 140 mg/dL with a flat arrow means something very different from 140 mg/dL with a double arrow pointing up. You can also share your data in real time with family members or caregivers through Dexcom’s Follow app, which is particularly useful for parents monitoring a child’s glucose at school.
At the end of the sensor’s life, the app notifies you, and you peel off the old sensor and apply a new one. The adhesive generally holds well through daily showers and exercise, though some people with sensitive skin use additional adhesive patches or skin-prep wipes to prevent irritation over the 10- or 15-day wear period.