The Dexcom G7 is a continuous glucose monitor (CGM) that measures your glucose levels every five minutes through a tiny sensor just beneath your skin. It converts glucose in your body’s fluid into an electrical signal, translates that signal into a number, and sends it wirelessly to your phone or smartwatch. The entire system runs without fingerstick calibrations.
The Sensor Chemistry
The G7 works by reading glucose not from your blood, but from interstitial fluid, the thin layer of fluid that surrounds your cells just below the skin’s surface. A hair-thin sensor filament sits in this fluid and is coated with an enzyme called glucose oxidase. When glucose molecules in the fluid contact this enzyme, a chemical reaction breaks them down and produces hydrogen peroxide as a byproduct. That hydrogen peroxide generates a tiny electrical current, and the strength of the current is directly proportional to how much glucose is present. More glucose means a stronger signal.
This is why CGM readings can lag a few minutes behind a traditional fingerstick meter. Your blood glucose changes first, and the interstitial fluid follows shortly after. The delay is typically around five minutes, which is close enough for real-time decision-making but explains why the two numbers won’t always match if you compare them side by side.
What You Wear on Your Body
Previous Dexcom models required you to attach a separate transmitter to a disposable sensor pod. The G7 combines both into a single unit. You apply it once, and the whole thing comes off together when the session ends. The integrated design is about 60% smaller than the G6, measuring roughly 1.1 by 0.9 by 0.2 inches. It’s about the size of a small coin and thin enough that most clothing covers it completely.
You apply the sensor using a one-press applicator that inserts the filament automatically. For adults, the approved placement sites are the back of the upper arm and the abdomen. For children ages 2 and up, the upper buttocks is also an option. The adhesive patch holds the sensor in place for the full wear period, and the sensor is waterproof. You can shower, swim, or bathe with it on. It can be submerged in up to 8 feet of water for as long as 24 hours.
Warm-Up, Wear Time, and Grace Period
After you apply a new sensor, there’s a 30-minute warm-up period before readings start. During this time, the sensor is calibrating itself against your body’s chemistry. Once warm-up is complete, it begins sending glucose readings automatically every five minutes.
Each sensor lasts 10 days. When the session ends, you get a 12-hour grace period before the sensor fully shuts off. This gives you a window to apply a new one without losing coverage, which is especially helpful if your sensor expires in the middle of the night or while you’re away from home.
No Fingersticks Required
The G7 is factory calibrated, meaning the sensor comes pre-set from the manufacturer and does not require fingerstick blood samples to stay accurate. Older CGM systems needed you to prick your finger once or twice a day and enter the value to keep the sensor readings on track. With the G7, that step is eliminated entirely. You can still enter a fingerstick value if you want to fine-tune accuracy, but Dexcom does not require it.
Alerts and Predictive Warnings
Beyond showing your current glucose level, the G7 actively watches for dangerous trends. You can set custom high and low alerts at whatever thresholds matter to you. If your glucose crosses those lines, your phone or watch vibrates or sounds an alarm.
The most notable alert is the Urgent Low Soon warning. The system analyzes the speed and direction of your glucose trend and predicts whether you’re heading toward 55 mg/dL within the next 20 minutes. If it determines you are, it alerts you before you actually reach that dangerously low level. This predictive window gives you time to eat fast-acting carbs or take other steps before a severe low hits, which is particularly valuable overnight when you might not notice symptoms while asleep.
There’s also a fixed Urgent Low alert at 55 mg/dL that cannot be turned off, serving as a safety net regardless of your other settings.
Where Your Data Goes
The sensor transmits readings via Bluetooth to your smartphone or directly to a compatible Apple Watch. The Direct to Watch feature works without needing your phone nearby, which is convenient during exercise or any time you’d rather leave your phone behind. Compatible models include the Apple Watch Series 6 and newer, the SE (2nd generation), and both Ultra models, all running watchOS 10 or later. Android users receive data through their phone’s Dexcom app.
The app displays your current reading along with a trend arrow showing the direction and speed of change. A graph shows your glucose history over the past several hours, making it easy to spot patterns after meals, exercise, or sleep. You can also share your data in real time with up to ten followers through the Dexcom Follow app, letting a partner, parent, or caregiver see your numbers and receive alerts on their own phone.
Integration With Insulin Pumps
For people who use an insulin pump, the G7 can communicate directly with several automated insulin delivery systems. These pumps read the G7’s glucose data and automatically adjust insulin dosing in real time, creating a partially closed loop that reduces the number of manual decisions you need to make throughout the day.
Currently compatible systems include the Omnipod 5 (a tubeless, pod-based pump), the iLet Bionic Pancreas, and Tandem’s Mobi and t:slim X2 pumps. Each system uses the G7’s glucose readings differently, but the core idea is the same: the pump increases or decreases insulin delivery based on where your glucose is and where it’s heading, keeping you in range more of the time without constant manual input.
How Accurate It Is
CGM accuracy is measured using a metric called MARD, or mean absolute relative difference. It represents the average gap between the sensor’s reading and a laboratory blood glucose measurement. A lower number means higher accuracy. In general outpatient use, the G7 consistently performs in the single digits for MARD among adults, placing it among the most accurate consumer CGMs available. Even in more challenging clinical settings like critically ill hospital patients, a study published through the American Diabetes Association found the G7 achieved a MARD of 12.5%, outperforming the G6’s 15.2% in the same population.
Accuracy tends to be strongest in the middle glucose ranges and can be slightly less precise at very high or very low extremes. Factors like pressure on the sensor (sleeping on it), rapid glucose changes, or a sensor nearing the end of its 10-day life can also affect individual readings. If a number doesn’t match how you feel, a fingerstick can serve as a helpful cross-check.