Continuous glucose monitor

The first CGM system was approved by the FDA in 1999. Continued development has extended the length of time sensors can be worn, options for receiving and reading data, and settings for alerting users of high and low glucose levels.

The first iteration of the Medtronic MiniMed took glucose readings every ten seconds with average readings reported every five minutes. Sensors could be worn for up to 72 hours.[11]

A second system, developed by Dexcom, was approved in 2006. The sensor was approved for use for up to 72 hours, and the receiver needed to be within five feet for transmission of data.

In 2008, the third model was approved, Abbott Laboratories' Freestyle Navigator. Sensors could be worn for up to five days.[11]

In 2012, Dexcom released a new device that allowed for the sensor to be worn for seven days and had a transmission distance of 20 feet. Dexcom later introduced an app allowing data from the sensor to be transmitted to an iPhone. This system was approved for paediatric use in 2015.[11]

In September 2017, the FDA approved the first CGM that does not require calibration with fingerstick measurement, the FreeStyle Libre. The Libre is considered a "flash monitoring" system (FGM), and thus not a true ("real-time") CGM system.[12] This device could be worn for up to ten days, but required 12 hours to start readings.[13] and was followed by an updated device that could be worn for up to 14 days, and needed only one hour to start a new sensor.[14][15][16] The FreeStyle Libre 2 was approved in Europe in October 2018, and enabled configuration of alerts when glucose is out of range.

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. This is the first FDA-approved CGM to include a fully implantable sensor to detect glucose, which can be worn for up to 90 days.[17][18] The Eversense XL, a 180-day version of the system, was approved in Europe in October 2017.[19]

China develops and produces CGM systems. The first CGM system to be approved for the European Union is manufactured by Medtrum Technologies. The sensor's intended use is up to 14 days and measures glucose levels every 2 minutes via a smartphone application.[20] Medtrum was founded in 2008 and is based in Shanghai, China.

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. The TouchCare system comes with mobile applications, including a remote view application.[21] The TouchCare system has glucose alerts and requires calibration every 24 hours.[22]

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 customisable glucose alerts.[23]

Medtrum makes both CGM and insulin pumps, both controlled by a single smartphone application which enables the user to monitor glucose levels and trigger insulin delivery in a closed-loop system.

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 hypoglycaemia, have impaired hypoglycaemia awareness, or cannot monitor their own blood sugar levels but they or a carer could use a scanning device. Details differ in Scotland and Northern Ireland.[24]

Multiple invasive CGM solutions have been under development since the early 2000s.[31]

Senseonics has commercialized its 180-day Eversense XL sensing systems in both the U.S. and European markets. In June 2023, it announced what it deemed favorable safety and accuracy data for its 365-day sensor, suggesting it may be commercializable in the future.[32]

A solution built by U.S. firm GlySens, aimed to remove the need for an external reader by creating a sensor that could be implanted under the skin, that directly transmitted glucose values to an external app. As of August 2023, this undertaking has stalled and the system has not been approved anywhere and the company is defunct.[33]

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.[34] This technology is composed of a hydrogel microsensor that is placed under the skin subcutaneously in a non-surgical procedure. In a 2020 literature review several biomedical engineers supported Profusa’s claims that the non-surgical insertion procedure differentiates it favorably from Senseonics’ Eversense system,[35] as the latter requires a surgical procedure to insert and remove the sensor. The Profusa sensor allegedly also does not need to be removed because it overcomes the foreign body response. A reader is placed on the skin on top of where the sensor is, with the sensor transmitting a light signal to it. The sensor is claimed to last for three to six months. The is information then passed on to a smartphone where it can be tracked through an app.[36] 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.[37] Profusa has filed to go public via SPAC transaction.[38]

A similar approach was under development by another California-based company called Metronom Health.[39] This company has not released news releases, nor has any news covered any progress in terms of its research and development.

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.

Noninvasive approaches can be divided into interstitial fluid-based, radio frequency-based or breath-based. Interstitial fluid-analyzing sensors either use a device to analyze fluid on the skin or under the skin by sending infrared lasers to detect glucose levels in fluid. Radio frequency devices go through the skin and may derive glucose level information from blood directly.

Apple has reportedly been working on a noninvasive CGM that it seeks to integrate into its Apple Watch. In March 2023 it was reported to have established proof-of-concept of a noninvasive CGM.[40] Another company working on noninvasive CGM is Masimo, which sued Apple for patent infringement in this area in 2020.[41] 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.[42]

Samsung announced that it would be incorporating glucose monitoring with its smartwatch with a targeted release year of 2025. As of October 2023 the last update was in December 2022. It is not clear whether the watch will integrate readings from an external CGM such as Dexcom's or Abbott's, or work standalone.[43] 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.[44] The company has filed patents related to this technology.[45]

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. The patch can be used for 24 hours. Electronic currents are used to draw interstitial fluid to the surface to analyse the glucose level. SugarBeat has achieved regulatory approval in Saudi Arabia[46] and Europe,[47] though market penetration rates remain very low. The company declared US$503,906 in revenue for the fiscal year ending March 2022,[48] which compares to Dexcom's more than $3 billion.[49] As of August 2023 it had submitted a US FDA premarket approval application for sugarBEAT.[50]

Another noninvasive system is built by US company Movano Health. It uses a small ring placed on the arm. 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.[51] Movano is listed as MOVE on NASDAQ. By August 2023 Movano had shifted to building sensor rings for other parameters, such as heart rate, blood oxygen levels, respiration rate, skin temperature variability, and menstrual symptom tracking.[52]

DiaMonTech AG is a Berlin, Germany-based privately-held company working on DTech, a CGM that uses infrared laser technology to scan the tissue fluid in the skin and detect glucose molecules. Short pulses of infrared light are sent to the skin, which are absorbed by the glucose molecules. This generates heat waves that are detected using its patented IRE-PTD method.[53] The company claims a high selectivity of its method, but no evidence has been published.

BOYDsense, based in Toulouse, France, is developing a sensor that measures glucose in the breath through the detection of volatile organic compounds (VOCs), a large group of carbon-based molecules that are gaseous at room temperature.[54] The system is in its preclinical development stage and has not received regulatory approval.

The BioXensor developed by British company BioRX uses patented radio frequency technology, alongside a multiple sensor (also capturing blood oxygen levels, ECG, respiration rate, heart rate and body temperature) approach.[55] The company claims this enables the measurement of blood glucose levels every minute reliably, accurately, and non-invasively. BioXensor had not received regulatory approval as of June 2023.

Israeli company HAGAR completed a study of its GWave non-invasive CGM, reporting high accuracy. This sensor uses radiofrequency waves to measure glucose levels in the blood.[56] The device had not received regulatory approval anywhere as of August 2023. One of the criticisms of radiofrequency technology as a way of measuring glucose is that studies in 2019 found that glucose can only be detected in the far infrared (nanometer wavelengths), rather than radiofrequencies even in the centimeter and millimeter wavelength range, putting into question the viability of radio frequencies for measuring glucose.[57]

Glucomodicum is based in Helsinki, Finland. Their attempted solution uses interstitial fluid to non-invasively measure glucose levels continuously. It does not have regulatory approval.[58]

KnowLabs is a U.S company building a CGM called the Bio-RFID sensor, which works by sending radio waves through the skin to measure molecular signatures in the blood, which Know Labs' machine learning algorithms use to compute the user's blood sugar levels. The company reported that it had built a prototype, but had not attained regulatory approval as of August 2023.[59]