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A Critical Review & Comparison of the Dexcom G7

article by gary scheiner

Gary tries the G7

Gary tries the G7

Seven is usually considered a lucky number.  Rolling a 7 in craps is a win.  There are 7 Wonders of the World.  And it’s no coincidence that Snow White had exactly 7 dwarfs to watch over her.

The trend continues with the Dexcom G7 – the latest CGM (continuous glucose monitor) to enter the marketplace.

For those who have been in a coma for the past ten years, a CGM is a device that measures glucose concentrations in real-time every few minutes. A tiny metallic sensor, placed below the skin with a spring loaded insertion device, generates a tiny electric current based on the glucose concentration.  The electrical signal is transmitted to a receiver, which interprets the signal and displays the data in numeric and graphic format.  The receiver, which can take the form of a smartphone, insulin pump, or handheld device provided by the manufacturer, can alert the user of high or low glucose levels.  The glucose and trend can be viewed on a smartwatch, but at present still requires the use of a smartphone to receive the transmission from the sensor and allow it to sync and display on the watch face.

the dexcom g7

Dexcom G7 Pros


Dexcom G7 will replace the Dexcom G6, which has been the market leader among those on intensive insulin therapy for several years.  G7 does many of the same things as G6: data updates every 5 minutes for 10 days per sensor, direction arrows, customizable high/low and rate-of-change alerts, predictive “urgent low” alerts, no calibration required (but calibration by way of fingerstick is still allowed), and the option of using a Dexcom handheld receiver or smart device for displaying data.


So what is “new and improved” with G7, other than it being “1” better?  Plenty.  Here are the top 7:

1. Accuracy has improved.  The MARD value (Mean Absolute Relative Difference – the average discrepancy between the sensor value and a lab value) is down to 8.2% for adults, 8.1% for kids aged 7-17, and 9.3% for kids under age 7.  This sets the standard in the CGM market, and is about 10% better than the G6’s MARD (which was around 9% overall).  Nearly 90% of the glucose values generated by G7 are within 15% of lab values (or within 15 mg/dl if the reading is below 100).

2. The sensor itself is about 60% smaller, and much flatter.  There is no need to attach a transmitter to the sensor; the transmitter is built right into the sensor.  The sensor filament is about 50% shorter. It inserts perpendicular to the skin (not at an angle), which may lead to a reduction in erroneous “compression lows”.

3. The warmup time is considerably shorter – only 30 minutes (actually closer to 27 minutes).  And for those who want to take the warmup time down to zero minutes, it is possible by placing the new sensor on the skin 30 minutes before the old one expires.

4. There is a “grace period” after the 10-day sensor session has ended.  The system will continue to work for up to 12 additional hours.

5. There are a number of new ways to customize the high/low alerts that make them more actionable and less of a nuisance.  For starters, the user can set thresholds at which rise/fall alerts take place.  For example, if the glucose is falling fast, the user can set an alarm to occur only if this takes place when the glucose is below 130 mg/dl.  It is also possible to set high alerts to only occur if the glucose is above the high threshold for a specified period of time. That way, temporary highs that occur after soon meals won’t trigger meaningless alerts.  The US version of G7 offers a “quiet mode” feature that sets all alerts to vibrate, except for unconfirmed urgent low alerts, for up to six hours.

6. Clarity features are built right into the Dexcom G7 app. Just scroll down the screen to see important data such as recent average and time-in-range.

7. Events (food, insulin, exercise) can be logged more easily. There is an icon right on the G7 home screen for event entries.

dexcom-g7 review

Dexcom G7 Cons


There are a few relatively minor downsides to the G7 compared to G6.  Because the adhesive patch is smaller and the company recommends wearing it on the arm, there is more likelihood of the sensor coming off before 10 days of use.  Dexcom provides an “overpatch” with each sensor to help with adhesion and stability.

Dexcom is clearly the CGM market leader when it comes to connectivity with other devices and software. However, connectivity requires an agreeable partner. Users of DIY Loop can already utilize Dexcom G7 when upgrading to version 3.0, but users of Tandem’s Control IQ and OmniPod5 will have to wait until the companies update their device firmware to be compatible with G7. In the case of Tandem, that should take place within a few months since a simple software patch is all that’s needed. In the case of Insulet, it may take considerably longer since each pod has to be rebuilt with new firmware. Users of InPen will also have to wait until Dexcom and Medtronic come to an agreement before G7 data will sync with the InPen app.

How much does the dexcom g7 cost?


The list price for a 3-pack of G7 sensors is similar to the price of G6 sensors – around $200. 

However, keep in mind that there is no additional transmitter to purchase when using G7.  Medicare, most private health insurance plans and many Medicaid plans already cover G7.  For those whose private insurance does not yet cover G7, Dexcom has a special Simple Start program that limits the out-of-pocket cost for a 3-pack (30-day supply) of sensors to $89 at most major pharmacies. Pharmacists should be able to apply this automatically at checkout. For those without any insurance, the free Good Rx program provides about a 10% savings on the cash price.

bottom line


Overall, Dexcom G7 looks like a winner.  I still wish they could figure out a way to cut down on the amount of plastic waste (there is about 20% less plastic with the new inserter compared to G6, but it still seems like too much).  And the Clarity reports, while simple to use, could be re-designed to provide better insight.  But G7 will certainly improve the lives of countless people with diabetes.

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