- βSenseonics 365-day Eversense demonstrated ~8-9% MARD accuracy maintained across the full year in the PROMISE trial
- βCE Mark already granted in Europe, providing real-world validation ahead of anticipated U.S. FDA clearance
- βFluorescence-based optical technology resists biological degradation that limits conventional electrochemical sensors
The Problem With Current CGMs
Continuous glucose monitors have transformed diabetes management, but they come with a persistent frustration: you have to replace them every 7 to 15 days. That means dozens of insertions per year, ongoing supply costs, and a steady stream of alerts reminding you to swap out your sensor. For millions of people living with Type 1 and Type 2 diabetes, the inconvenience is real.
That's why the race to develop a fully implantable, long-duration CGM β one that works for an entire year on a single insertion β has become one of the most closely watched frontiers in diabetes technology.
How Implantable CGMs Work Differently
Traditional CGMs sit just under the skin and measure glucose in the interstitial fluid using an electrochemical sensor. Because these sensors degrade quickly due to the body's immune response and sensor fouling, they must be replaced frequently.
Long-term implantable sensors take a different engineering approach. They are designed to sit deeper in the subcutaneous tissue and use materials and coatings specifically engineered to resist the foreign body response β the biological process that causes the body to wall off and degrade implanted devices over time. Some designs also incorporate glucose-sensing chemistry that is more stable over months rather than days.
Senseonics Eversense: The Only FDA-Approved Implantable CGM
The furthest along in clinical reality is Senseonics and its Eversense platform. The Eversense E3 system received FDA approval in 2022 for 180-day wear, and Senseonics has been actively developing the next generation β a 365-day sensor β which represents the clearest path to a true year-long device.
The 365-day Eversense system uses a fluorescence-based optical sensing technology rather than the electrochemical approach used by wearable CGMs like Dexcom and Abbott. A small capsule roughly the size of a small pill is implanted by a clinician under the skin of the upper arm. An external smart transmitter worn over the implant site reads glucose levels every five minutes, vibrates to alert the user of highs and lows, and transmits data to a smartphone app.
The optical fluorescence approach is central to why the sensor can last longer β the chemistry involved is more resistant to the biological degradation that limits electrochemical sensors.
Clinical Trial Data: What the Science Shows
Senseonics completed the PROMISE trial, which was the pivotal U.S. study supporting the 365-day sensor submission to the FDA. The PROMISE trial enrolled adults with diabetes and evaluated accuracy, safety, and sensor longevity over a full year of wear.
Published results showed that the 365-day sensor achieved a mean absolute relative difference (MARD) β the standard accuracy metric for CGMs β in the range of approximately 8 to 9 percent across the full year. For context, leading wearable CGMs typically report MARDs of around 8 to 10 percent. Critically, the sensor maintained consistent accuracy across the entire 365-day period without a significant decline in performance in the later months, which was a key concern entering the trial.
Safety data showed the insertion and removal procedures were well-tolerated. The most common adverse events were related to the implantation site, including minor bruising and discomfort, which are consistent with any minor surgical procedure.
Current Status
As of 2025, Senseonics submitted the 365-day Eversense system to the FDA for regulatory review. The FDA granted the device Breakthrough Device Designation, which is designed to expedite review for technologies that address unmet medical needs in serious conditions. Senseonics has indicated that the 365-day system is its primary commercial priority, with the expectation of bringing the product to U.S. patients following regulatory clearance.
The 365-day Eversense system has already received CE Mark approval in Europe, meaning it is available to patients in several European markets. This is a meaningful signal β regulatory approval in a major market provides real-world performance data and builds confidence in the technology ahead of U.S. clearance.
Outside of Senseonics, other companies β including efforts by larger CGM players exploring next-generation implantable platforms β remain in earlier research and development stages. No competing 365-day implantable CGM product is currently in late-stage pivotal trials in the United States.
What This Means for Patients
If the 365-day Eversense receives FDA clearance as expected in 2025, it would represent a genuine shift in what's possible for diabetes management. Instead of inserting a new sensor every week or two, a patient would visit a clinician once a year for a quick, minor outpatient procedure. Day to day, the experience involves wearing a small external transmitter β no repeated skin punctures.
However, there are honest trade-offs to understand. The external transmitter must still be worn and charged. The transmitter can be removed briefly for activities like swimming or showering depending on the model version. The implantation and removal do require a trained healthcare provider, meaning this is not a self-managed process the way current CGMs are. And cost and insurance coverage remain open questions that will depend heavily on payer decisions following FDA approval.
For patients who are highly motivated by reducing the burden of frequent sensor changes β particularly those with sensor fatigue, skin reactions to adhesives, or difficulty with self-insertion β the 365-day implantable CGM represents the most compelling near-term advancement in glucose monitoring technology available.