Implantable Fluorescence Sensors (Eversense)

Introduction to Implantable Fluorescence Sensors: Eversense E3

Eversense, made by Senseonics, is a continuous glucose monitor (CGM) whose sensor sits entirely under the skin rather than on a thin wire beneath an adhesive patch. The heading above names the Eversense E3, a 180-day version FDA approved in February 2022 [4]. As of October 2026, Senseonics' newest system is the Eversense 365, which FDA cleared in September 2024 for up to one year of wear in adults [3]. Below, "Eversense" means what the two share, and we name the model wherever they differ.

The chemistry is what sets it apart. Dexcom's G7 15 Day sensor is a typical enzymatic design: glucose oxidase reacts with glucose and the sensor measures the resulting electrical current [6]. Eversense coats a small cylinder, about 3.5 by 18.3 mm, with a hydrogel holding a fluorescent indicator. Glucose binds reversibly to a boronic acid group in that indicator, and the glow gets brighter as more glucose binds [2][3]. The implant has no battery of its own. The external transmitter powers it by radio frequency, reads the fluorescence and converts it into a glucose value every 5 minutes [1][3].

Key Features and Differentiators

• Longevity: The Eversense 365 sensor is cleared for up to one year and the E3 for up to 180 days, compared with up to 15 days for the Dexcom G7 15 Day [3][4][6]. A year of wear doesn't mean a year without fingersticks. After a 24-hour warm-up, the 365 asks for four fingerstick calibrations within 36 hours, then one a day through day 13, then one a week [3].
• Accuracy: The PROMISE Study followed 181 people with diabetes for up to 180 days. It reported a mean absolute relative difference (MARD, the average gap between sensor and lab readings, so lower is better) of 9.1% for the standard sensor and 8.5% for a modified sensor with an added "sacrificial" boronic acid designed to resist oxidation [2]. For the Eversense 365, FDA's decision summary reports that 92.0% of readings fell within 20% of a laboratory analyzer across a year of wear in the 110-person ENHANCE study [3].
• Alerts: The transmitter vibrates on the body for alerts, so a warning still reaches the wearer when the phone is out of reach. FDA described this feature when it approved the first Eversense in 2018 [1].
• Pump connection: The Eversense 365 is cleared as an integrated CGM (iCGM), an FDA device category for sensors designed to send readings to automated insulin delivery (AID) systems [3]. As of October 2026, the twiist AID System lists the Eversense 365 as a compatible sensor [5].

Critical Considerations and Pitfalls

• Interference: The labeling warns about errors in both directions. Mannitol or sorbitol given intravenously, or as part of an irrigation or peritoneal dialysis solution, can cause falsely high readings, while sorbitol from ordinary food doesn't [3]. Tetracycline-class antibiotics, including doxycycline and minocycline, push the other way and can falsely lower readings [3]. Here's what surprised us: that falsely low tetracycline warning isn't new, since it already appeared in the labeling of the first 90-day Eversense in 2018 [1]. How to check glucose during a course of those antibiotics is a question for your care team.
• Procedure: A trained clinician inserts the sensor through a small incision, which Senseonics says is usually closed with adhesive strips rather than stitches [7]. Removal is also a clinic procedure [1]. A silicone collar on the sensor releases 1.75 mg of the steroid dexamethasone acetate to calm inflammation around it, which is why the system is contraindicated for people who shouldn't receive dexamethasone [1][3].
• Form Factor: The implant can't be seen, but the transmitter can. It sits on the skin over the sensor, held by an adhesive patch, and needs a charge every day [1][3]. FDA labels the smart transmitter MR Unsafe, so it has to come off before any MRI scan [3].

Conclusion

Eversense swaps the sensor change every week or two for a clinic visit about once a year, and the Eversense 365 now feeds an AID pump as well [3][5]. The open question is real-world accuracy over a full year. FDA's figures for the 365 come from 110 adults measured during scheduled clinic visits [3]. Whether that trade makes sense, especially for anyone who takes tetracycline-class antibiotics or can't receive dexamethasone, is a decision to make with a care team.