Medical review byElizabeth Gomez, MSN, FNP-BC
You’ve got a continuous glucose monitor (CGM), but where should you stick the sensor onto your body? This is a common question for CGM users.
There are lively debates in the diabetes community over the best place to wear your CGM, with many preferring alternative sites that directly contradict the advice of the manufacturers.
This article will explore both the official word on the subject, scientific evidence of accuracy, and the opinions of Diabetes Daily community members. Let’s find the best CGM location for you!
Image courtesy of Dexcom
In This Section
- 1 Dexcom
- 2 FreeStyle Libre
- 3 Medtronic Guardian Connect
- 4 Where Diabetes Daily Readers Place their CGM Sensors:
- 5 The Bottom Line
The Dexcom G6 is officially approved for use in either one or two locations, depending on the user’s age. All users can place the G6 sensor on the abdomen or back of the upper arm. Children (ages 2-17) are additionally approved to use it on the upper buttocks.
The Dexcom G7 — which has only recently been released, but is not yet available to all customers — can be worn on the upper arm. A clinical trial showed that readings from this site were just as accurate.
In addition, users are warned to place the sensor “at least 3 inches from any insulin pump infusion set or injection site” and “away from waistbands, scarring, tattoos, irritation, and bones.”
Dexcom warns that improper use could result in inaccurate readings and dangerous blood sugar excursions—a warning that many users have found to be overblown. In reality, a very large percentage of Dexcom users prefer to place their sensors on their upper arms, and have few concerns about any loss of accuracy.
Some scientific data suggests that the Dexcom G6 is indeed just as accurate in unapproved locations. For example, this 2020 study of pregnant women found sensors “performed well whether placed on the abdomen, buttock, or posterior upper arm,” and that the back upper arm actually had the best accuracy of the three sites.
Photo by FreeStyleLibre.us
The FreeStyle Libre system — whether the Libre 2 or the newly-released Libre 3 — has only one officially approved area for sensor application. The instructions explain:
Apply Sensors only on the back of your upper arm. If placed in other areas, the Sensor may not function properly and could give inaccurate readings. Avoid areas with scars, moles, stretch marks, or lumps.
While the arm is almost certainly the most popular place to wear a Libre sensor, some Libre users, just like many Dexcom users, do their own thing. Some prefer to use the abdomen, thighs, or chest, although none of those spots are approved by the company or validated by the FDA.
Are alternative sites accurate? Just as we saw with the Dexcom, the science suggests that other sites may also provide reliable glucose measurements. This 2022 study, for example, found that Libre sensors placed on the back and chest were 98% as accurate as sensors on the arm. You can also find many anecdotal reports on Youtube and throughout the diabetes online community comparing sensor accuracy in different sites — and, generally speaking, most people seem to believe that the sensors work well just about everywhere. With that said, a 2018 study of the earlier generation FreeStyle Libre found that “the abdomen performed unacceptably poorly,” so it may be smart to be cautious.
Image source: Medtronic
Medtronic Guardian Connect
Medtronic’s CGM is less popular with our readers than its competitors, but many still rely on it as part of the company’s MiniMed 670Gand the630Ginsulin pump systems.
The Guardian Connect is approved for use in the abdomen or the back of the upper arm at a site “that has an adequate amount of fat.”
If you look deep in the user manual, you’ll find pages of data comparing the accuracy of the abdomen and upper arm in different situations. These suggest that the arm is slightly more accurate than the abdomen, but the differences are probably small enough as to be almost completely unnoticeable. Both sites are also slightly more accurate if they’re calibrated more frequently.
Where Diabetes Daily Readers Place their CGM Sensors:
We’ve conducted an informal poll on our Facebook page and pored over comments in our forum. After reviewing well over a hundred responses, we can report that these are the most popular sensor sites:
No matter the model of CGM, the arm is the most popular choice in our community. Most users choose to apply their CGM sensors to the back of the arm, where the sensor is less likely to swipe against door frames. It’s considered comfortable for sleeping, and it may help the adhesive stick longer because the tricep doesn’t twist and flex as much as the abdomen does.
As discussed above, the arm is approved as a location for the Medtronic Guardian sensor, the Dexcom G6, and the FreeStyle Libre 2 and 3.
The abdomen is clearly the second most popular option.
So many people with diabetes have experience with insulin pumps on their bellies that it can just feel natural to slap a CGM sensor on there too. The abdomen is the one approved spot for adults using the Dexcom G6, and is one of two spots approved for the Guardian Connect. It also keeps the sensor hidden at work (unless, perhaps, you’re a lifeguard).
Moving beyond the arm and the abdomen, we come to the less popular options. It is only a committed minority of mavericks that use the following sensor placement locations:
The thigh is not approved for any of the CGM systems, but it remains a popular alternative choice for those that feel comfortable breaking the rules. Some users find that the outside of the thigh is more out of the way and less obtrusive than the arm, although opinions differ on exactly where it should go, with some choosing the front of the thigh or even the inside. The thigh placement is also more often hidden by clothing, making it a discrete choice for those that find a device on the abdomen uncomfortable. Sensor accuracy cannot be guaranteed at this site, but many find that it works quite well.
Last but perhaps not least, a few of our readers prefer to wear their CGM sensors on the chest. One major benefit is that the sensor may be less likely to get ripped off. And unlike the abdomen, the upper chest does less twisting and contorting, which may improve the durability of the adhesive.
The host of Type One Talks, a diabetes Youtube channel, rates the chest as the best alternative site for the Freestyle Libre. In the following image, the circle represents the area he recommends placing a Libre sensor:
Screengrab from Type One Talks
We found no academic studies evaluating the accuracy of readings from the chest, and none of the devices are intended to be used there. But anecdotal evidence suggests that it may work just as well as any other part of the body.
Some of our community members choose none of the positions named above, and instead put their sensors on their calf, upper buttocks, forearm, and perhaps even other body parts that we haven’t even mentioned in this article. There is a risk that these alternative sites may be inaccurate, as they haven’t been formally tested, let alone formally approved by health regulators.
The Bottom Line
The safest and most reliable sensor placement is the one recommended by the manufacturer. When you use the arm and/or abdomen as recommended, you can be fairly sure that your CGM system is set up to work exactly as intended.
However, while we cannot recommend the practice, some people with diabetes opt for alternative sites for a variety of reasons, including superior comfort, discretion, durability, ease of application, quality of adhesion, and protection from knocks and bumps.
Read more about Abbott FreeStyle Libre, continuous glucose monitor (CGM), Dexcom, sensor.