If you’ve ever dreamed of having your glucose levels monitored automatically by a tiny implantable sensor that beams the data to a smartphone, the Eversense continuous glucose monitor (CGM) may be the product for you.

Maryland-based Senseonics has made this dream a reality with Eversense, the first long-term continuous glucose sensor the size of a small twig that is implanted under the skin for up to 90 days to monitor your glucose readings in real-time. You don’t have to keep replacing the sensor every week or so, like other CGMs require.

Eversense has been available in the United States since mid-2018 and has been sold by fingerstick meter manufacturer Ascensia Diabetes Care (formerly Bayer) since a 2020 collaboration that saved Senseonics from sales woes as a result of the COVID-19 pandemic.

Traditional CGMs consist of a sensor worn externally on the abdomen or arm that takes glucose readings via a tiny cannula (built-in plastic tube). The sensor is typically worn for 7 to 10 days before you need to replace it, using an autoinserter device that comes with the system.

The Eversense is entirely different. It’s a first-of-its-kind sensor that is implanted under the skin for 3 months. To get readings, you do have to wear an external transmitter over the sensor insertion site with an adhesive backing, but this is something you just slap on like a Band-Aid.

Note that the transmitter is a black square, so not particularly discreet. But the upside is that you can take it off whenever you wish, without wasting anything but a single adhesive backing. The package includes a set of 100 adhesives — 90 regular white and 10 clear ones (that look more attractive but tend not to stick as well).

While Eversense had been available in Europe and more than a dozen other countries since May 2016, it took about 2 years to get through the full Food and Drug Administration (FDA) regulatory process. The agency approved the Eversense CGM in June 2018. It is currently only approved for use in adults ages 18 years and older.

Here are the basics of the system:

Tiny sensor. The sensor is a tiny, transparent rod thinner than a Tylenol tab that’s implanted completely under the skin. It’s FDA-approved to go in the upper arm, though some users internationally have reported having had it inserted on their abdomen. Once inserted, the sensor has a one-time warmup period of 24 hours.

Doctor’s office implantation. Insertion takes place in a doctor’s office in a less than 10-minute implant procedure. All that’s needed is lidocaine and a specially designed tool to insert the sensor in a pocket of skin about twice as deep as a regular CGM cannula would go.

Three-month wear. The United States-approved version currently lasts up to 90 days before needing replacement. You have to return to the doctor’s office to have the sensor removed, and a new one implanted in the other arm for rotation. Training doctors to do this procedure smoothly — especially the removal — has been a huge priority for Senseonics since the moment of FDA approval.

Black transmitter, needs charging. As noted, the rub for some folks may be the need to wear the transmitter on the skin, attached with an adhesive directly above the inserted sensor. The transmitter is a flat black disc, a little thinner than two stacked quarters. It’s smaller than an OmniPod patch pump but bigger than the FreeStyle Libre sensor. It sends data to the companion smartphone app every 5 minutes. The transmitter can be removed and re-attached as often as desired, for a shower or sports, but naturally no data will be transmitted while it is off. It also needs to be recharged daily using a cable provided for 10 to 15 minutes. The transmitter has a hard shutoff at 90 days based on an internal clock, so in case you’re wondering, there is no possibility to restart an expired sensor.

Fingersticks required. Per the FDA, this system still requires two fingerstick calibrations per day. The app will prompt you to add those numbers at two times of day of your choosing.

Light-sensing tech. The device uses novel, proprietary light-based technology to measure glucose levels. The sensor is coated with a fluorescent chemical that, when exposed to blood sugar, produces a small amount of light that is measured by the sensor.

On-body vibration. One very cool feature is that the Eversense transmitter actually vibrates on the body to alert users to highs and lows, varying the amount of vibrations depending on where glucose levels are. This means you can disable all the annoying audio alerts if you so choose.

No receiver, smartphone only. What’s also novel is that this system does not include a separate receiver as an option to smartphone connection. That means to use it, you must have an Android or iOS device (iPhone, Android, iTouch, iPod, or tablet). While the straight-to-phone connectivity is an exciting trend, it’s also a potential roadblock for some people.

Mobile app. The app display a colored bar at the top that shows you plainly in Red, Yellow or Green where you stand in terms of target range. The clear, easy-to-use Menu includes an Alert History, where you can see records of every High Alert, Low Alert, Transmitter Disconnected or Calibrate Now alert received, with exact day and time. This is super useful for going back over your day or week to retrace your steps.

The Event Log is equally clear and easy to navigate, and appears to contain at least a month’s worth of detailed info if you continue to scroll back.

The Reports section shows you a Weekly Modal Summary; a Glucose Pie Chart for 1, 7, 14, 30, or 90 days’ worth of data; and Glucose Stats Report with the same 1- to 90-day options, displaying your average, highest and lowest readings, and standard deviation broken in four sections by time of day (12 a.m. to 6 a.m., 6 a.m. to 12 p.m., 12 p.m. to 6 p.m., and 6 p.m. to 12 a.m.). To email any of these reports to a recipient of your choice, you just click on the Share icon in the upper right of the screen. If you click into the Share My Data area, you can also send email invitations to your doctors or loved ones to be able to view your continuous stream of data, including alerts and events logged.

Predictive alerts. Along with the traditional Low, High, and Rate of Change alerts, the Eversense can predict when you’re going to go Low or High as much as 10 to 30 minutes in advance, providing those predictive alerts either via the on-body vibration feature or via the mobile app, which can give an audible alert or even flash a light to catch attention.

The standard measurement of CGM performance is known as the mean absolute relative difference (MARD). With this measure, the lower the number, the better the accuracy.

Clinical study data shows the Eversense 90-day product has a MARD score of 8.5% to 9.6%, putting it on par or above other CGM technology available in the United States.

In 2018, Eversense won out in a 3-way comparison against Dexcom’s then-G5 model and the original Abbott FreeStyle Libre flash glucose monitor.

You need a doctor’s prescription to get Eversense, and if your diabetes doctor is not yet trained to do the insertion, you work with the company to find an authorized provider to handle that.

Users seem to universally praise the accuracy they get with this system — including lack of dropped connection that is common with other CGMs. They’re also very enthusiastic about the vibrating alerts, that offer freedom from all those annoying beeps, and the flexibility that the removable transmitter provides.

For example, Megan Casey, a diabetes advocate who works at JDRF, told Beyond Type 1: “Before, with my CGMs, they would alert me with a ringtone. And when the audio alert would go off, letting me know my blood sugar was low or high, everybody in the room would know something was going on… Now, it’s really nice because with my Eversense, it vibrates on my arm, and I can turn off the audio alarm. I can discreetly treat a low blood sugar when I’m doing my training, and it doesn’t have to interrupt my life.”

Southern California-based physician assistant Nalani Haviland-Hunsaker shared: “My favorite feature of Eversense is the on-body vibe alerts. I consider myself a very active person and I’ve always been a water girl. The light, low-profile transmitter sits over the sensor on the upper arm and can be submerged in 1 meter of water for up to 30 minutes.”

“I also struggled with catching my CGM on my pants or swimsuit, and especially on my sports bra. All you ladies out there know what I mean. I’ll never forget the first time I got my Eversense caught on my shirt and it fell off. I had a short freak-out until I realized that all I needed to do was stick it back on. It was so easy!” she added.

Our own Amy Tenderich, founder and editor of DiabetesMine, wore the Eversense for over a year and recorded her experiences.

“The app does not often disconnect or lose signal, and if it does, it’s easy to fix. Just go to the Menu, and click ‘Connect,'” she reported. “The few times when that didn’t work, I simply exited the app altogether and then re-opened it, and it reconnected immediately.”

On the downside, she wrote: “As noted, the Eversense transmitter needs to be charged every single day for about 15 minutes, and then re-attached to your arm with a fresh adhesive. Yes, this is something you kind of need to plan your day around, otherwise you can easily forget and the system will run out of juice.” The other downside for Tenderich was small scars on both shoulders after repeated insertions and removals.

Respected Pennsylvania-based diabetes care and education specialist Gary Scheiner praised the accuracy and ease of use of the Eversense system, but wrote:

“Personally, I found the glucose trend graph displays on the app to be visually awkward. They could have taken a lesson from the other CGM manufacturers in designing their display screens. While the reports are simple to generate, there is no ‘overlay’ report for quick detection of patterns and establishing cause/effect relationships. I also found the app to drain my cellphone battery faster than the apps for other CGM systems. And for some reason, the app does not allow the user to set their high/low alerts within their target glucose range — something the software engineers need to fix ASAP.”

There is a future version under development of this implantable CGM known as the Eversense XL, which would allow for the same tiny sensor to be implanted for 180 days (or 6 months rather than 3). That version would also reduce the number of fingerstick calibrations needed to one per day, according to the company.

In October 2020, Senseonics asked the FDA to approve the 180-day wear version, and that submission remains pending as of mid-2021.

There are several other CGM systems on the market, none of which are implantable, but all essentially do the same thing in continuously monitoring glucose data:

  • Dexcom G6. This is the market-leading “traditional” CGM device with a sensor and transmitter design, providing automatic continuous results every several minutes. You insert a small oval-shaped unit onto your body that houses both the sensor and transmitter. Each G6 sensor is labeled to last up to 10 days, while the transmitter portion has a 90-day battery life and is used with each new sensor until it runs empty. The G6 also offers advanced alert and alarm options, like “Urgent Low,” “Urgent Low Soon,” “Rise Rate” and “Fall Rate.” This CGM currently integrates with insulin pumps including the Omnipod and Tandem t:slim X2. Dexcom G6 is approved for use in people with diabetes ages 2 years and up.
  • Medtronic’s Minimed Guardian Connect. This stand-alone CGM sends updates, notifications, and predictions to your smartphone. Like the Dexcom, it can help stabilize glucose levels. But it is only approved for 7-day wear, and many users say the sensor is less comfortable on the body. This device is FDA-approved for people with diabetes ages 17 to 75.
  • Abbott FreeStyle Libre. This is a “flash glucose monitor” that consists of a little white circular sensor worn on your upper arm. You have to manually scan the sensor each time you want a reading, using a handheld receiver or smartphone app. The latest Libre 2 version offers 14-day wear and optional alerts for low and high glucose levels. The FDA has approved this device for kids as young as 4 years old.

Eversense users find the real-world accuracy to be excellent. They also love the flexibility of not having to worry about replacing sensors themselves every week or so, or carry insertion supplies. And Eversense offers the unique ability to take the external unit off and on any time you want without wasting a sensor.

If you don’t mind having to deal with a small surgical procedure every 3 months, and needing to charge this system for 10 to 15 minutes each day, you may find the Eversense extremely useful and freeing for managing your diabetes.