The sensor measures the glucose level of interstitial fluids (as a proxy for blood sugar levels) continuously; up to eight hours of these readings, averaged over each 15-minute period, are stored in the sensor unit, unlike most other CGM systems, which use a wireless link (typically Bluetooth) to an external device for each reading.

Continued development has extended the length of time sensors can be worn, options for receiving and reading data, and settings for alerting users to high and low glucose levels.

In June 2018, the FDA approved the Eversense CGM system (manufactured by Senseonics Inc) for use in people 18 years of age and older with diabetes.

[citation needed] At the end of 2017, Medtrum introduced the TouchCare A6 CGM (later A7 or Slim in some countries) which measures glucose levels in the interstitial fluid up to 14 days.

[25] At the end of 2021 the Medtrum Nano was announced, a very slim device not requiring calibration, approved for up to 14 days use, with customizable glucose alerts.

UK NICE guidelines introduced for the NHS in March 2022 in England and Wales advise that all Type 1 diabetic patients should be offered either flash glucose monitoring or CGM.

People with Type 2 diabetes should be offered flash glucose monitoring or CGM if they use insulin twice daily or more, are otherwise advised to finger-prick eight times a day, have recurrent or severe hypoglycemia, have impaired hypoglycemia awareness, or cannot monitor their own blood sugar levels but they or a caretaker could use a scanning device.

[30] The continuous glucose monitoring space remains subject to extensive research and development in building lower cost, more accurate and more easy-to-use sensing solutions, some of which aim to be noninvasive.

[31] A noninvasive CGM has been defined as a medical device that can measure glucose levels in the body without puncturing the skin, drawing blood or causing any pain.

[32] There have been regulatory approvals of noninvasive sensing systems in Europe,[33] though market adoption has been low, not affecting the Abbott-Dexcom dominance.

[37] Another invasive CGM technology under development by Profusa Inc, based in Emeryville, California, builds on sensing research projects previously undertaken by the company under DARPA grants.

[40] As of August 2023, this sensor has not attained regulatory approval in any jurisdiction, though a similar Profusa system measuring oxygen levels under the skin, has CE certification in Europe.

[45] The ease of use many CGM users expect would be provided by a safe and accurate noninvasive device has led to significant innovation and research.

[47] Masimo has also filed new patents through its subsidiary Cercacor (pending as of September 2023) covering a joint continuous glucose monitoring and pump-closed loop delivery system.

[49] The company in 2020 published literature regarding a non-invasive method it had developed with MIT scientists to engage in continuous glucose monitoring using spectroscopy.

[51] SugarBeat, built by Nemaura Medical, is a wireless non-invasive blood glucose monitoring system using a disposable skin patch.

The patch connects to a rechargeable transmitter which detects blood sugar and transfers the data to a mobile app every five minutes.

SugarBeat has achieved regulatory approval in Saudi Arabia[52] and Europe,[53] though market penetration rates remain very low.

Movano said in 2021 that it was building the smallest ever custom radio frequency (RF)-enabled sensor designed for simultaneous blood pressure and glucose monitoring.

[60] The company claims a high selectivity of its method, results of a first study have been published in the Journal of Diabetes Science and Technology.

[61] DiaMonTech has announced that its envisioned follow-up product D-Sensor, will feature continuous measurements, making it a CGM though no release date has been given.

Haifa, Israel-based company HAGAR completed a study of its GWave non-invasive CGM, reporting high accuracy.

In January of 2024, Liom (then called Spiden) declared it had developed a prototype, with a claimed MARD (Mean Absolute Relative Difference) value to a reference glucose measurement of approximately 9%.

[70] Occuity, a Reading, UK-based startup is taking a different approach to noninvasive glucose monitoring, by using the eye.

[71] The company is developing the Occuity Indigo,[72] which will measure the change in refractive index of the eye to determine the concentration of glucose in the blood.