Non-Invasive Glucose Sensing Technologies

Non-Invasive Glucose Sensing Technologies

Non-invasive glucose sensing (NIGS) means reading glucose without pricking a finger and without placing a sensor filament under the skin. As of October 2026, it remains a research goal rather than something you can buy in the US. The FDA says it has not authorized any smartwatch or smart ring that measures glucose on its own [6], and a 2022 review of products in development found that no noninvasive optical monitor had FDA clearance [1].

Categories of NIGS

A 2022 review splits the non-invasive approaches into optical methods and fluid sampling, which covers both pulling fluid through the skin and testing fluids the body releases [1]:

• Optical techniques: light goes into the skin and the returning signal is analyzed. Examples include Raman spectroscopy and optical coherence tomography (OCT) [2], as well as near-infrared spectroscopy [5].
• Transdermal extraction: reverse iontophoresis passes a small electrical current through the skin to pull out interstitial fluid, the fluid that surrounds skin cells, so a sensor can measure its glucose [1].
• Biofluid analysis: sensors test fluids the body releases on its own, such as tears and sweat [1].

History of NIGS

One attempt did reach the market: the GlucoWatch Biographer from Cygnus, Inc. [1]. The FDA approved it on March 22, 2001, for adults with diabetes, as an add-on to standard fingerstick meters rather than a replacement [3]. It used reverse iontophoresis, and that low-level current is where the trouble started: users complained of a burning sensation, the readings lacked enough clinical accuracy, and the product was discontinued [1][2]. A 2005 trial in 200 children with type 1 diabetes shows how that played out. Use of the GlucoWatch G2 Biographer dropped over six months. Skin irritation was the most common reason (76%), followed by skipped readings, excessive alarms and inaccurate readings [10].

Challenges in NIGS

Large technology companies have tried, and the hurdles held. Google's life-sciences company Verily, working with Novartis, built a contact lens to read glucose in tears, then halted that work in 2018 because its tear readings did not track blood glucose consistently enough for a medical device [4]. The 2022 review also listed an Apple Watch glucose add-on among the optical projects it found; it had no FDA clearance [1]. Two problems come up again and again:

• Physiological lag: glucose takes time to diffuse from blood into interstitial fluid, sweat or tears. When blood glucose is changing, those fluids trail behind, and the size of the delay differs from person to person [1].
• Low signal-to-noise ratio: glucose gives off a weak optical signal [1]. In near-infrared light it is often masked by water and hemoglobin [5], and skin pigmentation, skin thickness, body movement and room temperature add more noise [1].

Current State of NIGS

Two companies that drew attention in recent years show where commercial efforts stand:

• Know Labs developed a radio-frequency sensor and, in February 2024, said it planned to submit it to the FDA for clearance as part of a wearable non-invasive glucose monitor [11]. In August 2025 the company renamed itself USBC, Inc. and pivoted to financial technology [12], and in March 2026 it sold its legacy sensor business to a company controlled by its former chairman and CEO [13].
• Rockley Photonics builds infrared optical sensors and in 2021 listed glucose trends among the measurements its wearable sensor module was meant to track [14]. It filed for Chapter 11 bankruptcy protection in early 2023 to restructure and emerged that June [15].

ISO 15197 is the international accuracy standard for blood glucose meters. Its 2013 edition sets minimum accuracy criteria for results compared against a laboratory method [7]. It isn't the rule a US device has to meet, though. The FDA reviews home meters against its own September 2020 guidance, which asks over-the-counter meters to put 95% of results within ±15% and 99% within ±20% of the reference [8] (see ISO 15197:2013 and Regulatory Standards). A CGM built to feed data to automated insulin dosing systems must meet the iCGM special controls written into federal regulation. Among other criteria, the lower bound of a 95% confidence interval for the share of readings within ±20% of the reference must exceed 87%, and there is no MARD cutoff [9] (see iCGM Regulatory Standards). For now, the FDA tells people to measure glucose only with FDA-authorized devices, such as CGMs that pierce the skin [6]. Which device fits your diabetes care is a decision for you and your care team.