A Dexcom is a small wearable device that continuously tracks your glucose (blood sugar) levels throughout the day and night without fingerstick blood tests. It falls into a category of devices called continuous glucose monitors, or CGMs, and it’s one of the most widely used systems for people managing diabetes. The sensor sits just under the skin, takes a new reading every few minutes, and sends the data wirelessly to your phone or a small handheld receiver.
How the Sensor Works
Traditional glucose meters require you to prick your finger and place a drop of blood on a test strip. A Dexcom works differently. A tiny, flexible sensor filament is inserted just beneath the skin (usually on the back of the upper arm or the abdomen), where it sits in the fluid between your cells, called interstitial fluid. Glucose from your bloodstream naturally diffuses into this fluid, and the sensor measures it there.
Because glucose has to travel from your blood into that interstitial space, there’s a small physiological delay. Your Dexcom reading reflects where your glucose was roughly a few minutes ago, not at that exact instant. In practice, this lag rarely matters for day-to-day decisions, and the system compensates by showing you a trend arrow that indicates whether your glucose is rising, falling, or holding steady. That directional information is something a single fingerstick can never provide, and many users find it more valuable than the number itself.
What’s in the Box
The current flagship model, the Dexcom G7, has a streamlined design compared to earlier versions. The system requires a disposable sensor (which includes the transmitter built in), an adhesive overpatch to keep it secure, and a compatible display device. Most people use the Dexcom G7 app on their smartphone, though an optional standalone receiver is available for those who prefer not to use a phone.
The sensor is roughly the size of a quarter and sticks to your skin with an adhesive patch. You apply it yourself using a one-touch inserter, and the process takes a few seconds. The G7 has a 30-minute warm-up period after insertion before it starts displaying readings. Each sensor lasts 10 days, with an additional 12-hour grace period before you need to swap in a new one. The older G6 model, still in use, has a longer 2-hour warm-up but the same 10-day sensor life.
No Fingersticks Required
The Dexcom G7 is factory-calibrated, meaning it does not require routine fingerstick calibrations. You can apply the sensor and start getting readings without ever using a traditional blood glucose meter. If you want, you can still enter a fingerstick value into the app to fine-tune accuracy, but it’s entirely optional. This applies to both the standard G7 and the newer G7 15-Day version.
In clinical testing, G7 sensors placed on the arm had an overall accuracy error of about 8.2%, and sensors on the abdomen came in at roughly 9.1%. To put that in perspective, if your actual glucose is 150 mg/dL, the Dexcom reading would typically fall between about 138 and 162. For the vast majority of daily decisions, like whether to eat a snack or take a walk, that level of precision is more than sufficient.
Alerts That Warn You Before Problems Hit
One of the most important features for people with diabetes is the alert system. You can set customizable high and low glucose alarms so your phone buzzes when you drift outside your target range. The G7 also includes a predictive “Urgent Low Soon” alert: when the system estimates your glucose will drop to 55 mg/dL or below within the next 20 minutes, it warns you before you actually reach that dangerous level. This gives you time to eat or drink something to prevent a serious low.
These alerts are especially valuable overnight, when you’re asleep and wouldn’t otherwise notice a glucose drop. Parents of children with Type 1 diabetes often rely on the sharing feature, which lets up to 10 followers monitor glucose data remotely on their own phones.
Who It’s Designed For
The Dexcom G7 is FDA-cleared for people aged 2 and older with Type 1 or Type 2 diabetes. It requires a prescription. The device is not currently indicated for pregnant women, people on dialysis, or critically ill patients.
Medicare covers Dexcom CGMs for people with diabetes who take insulin or who have a history of problematic low blood sugar, provided a healthcare provider prescribes the device and confirms the user has been trained on it. Private insurance coverage varies, but most major plans now cover CGMs for insulin-dependent patients.
Integration With Insulin Pumps
For people who use an insulin pump, a Dexcom sensor can do more than just display numbers. It can communicate directly with certain pumps to create what’s called an automated insulin delivery system. The Dexcom feeds real-time glucose data to the pump, and the pump’s algorithm automatically adjusts insulin delivery, increasing it when glucose is rising and reducing or suspending it when glucose is dropping.
The Dexcom G6 currently integrates with the Omnipod 5 (a tubeless pod-based pump), the Tandem t:slim X2 with Control-IQ technology, and the CamAPS FX system used with Dana pumps. These closed-loop systems significantly reduce the burden of manual insulin dosing and help keep glucose in range more of the time, particularly overnight.
The Over-the-Counter Option: Dexcom Stelo
In addition to its prescription CGMs, Dexcom now sells a product called the Stelo, which is available without a prescription directly from the company’s website and in pharmacies. The Stelo is designed for a different audience: adults 18 and older who have prediabetes or Type 2 diabetes but don’t use insulin, as well as people without diabetes who simply want to understand how food, exercise, and stress affect their glucose.
The Stelo shares the same basic sensor technology but differs from the G7 in several important ways. It lasts 15 days per sensor instead of 10. It reads glucose between 70 and 250 mg/dL, displaying “below 70” or “above 250” for anything outside that window, while the G7 covers a wider 40 to 400 mg/dL range. Most notably, the Stelo does not have real-time high or low glucose alerts, which makes it unsuitable for anyone at risk of dangerous lows. It also cannot connect to insulin pumps or connected insulin pens.
What the Stelo does well is educate. Its app highlights glucose spikes and helps you connect them to what you were doing beforehand, whether that was eating a particular meal, sitting at your desk for hours, or going for a run. It’s positioned as a learning tool rather than a medical management device.
What Daily Life With a Dexcom Looks Like
Wearing a Dexcom is relatively unobtrusive. The sensor patch is water-resistant, so you can shower, swim, and exercise with it on. Most people forget it’s there after the first day or two. You glance at your phone whenever you want a reading, and the app stores your data in graphs that show patterns over hours, days, or weeks. Many users share these reports with their healthcare provider at appointments.
The biggest adjustment is information. Before CGM, someone with diabetes might check their glucose four to six times a day with fingersticks and fill in the gaps with guesswork. With a Dexcom, you see every rise and fall in real time. That can be empowering, but it can also feel overwhelming at first. The trend arrows and pattern reports help you learn what spikes your glucose (a bowl of rice, a stressful meeting) and what brings it down (a brisk walk, a good night’s sleep), turning abstract numbers into actionable habits.