No smartwatch or wristband that measures blood glucose has received FDA clearance or approval. Despite years of consumer anticipation and active research by major technology companies, no wearable in a watch form factor can legally claim to monitor glucose levels in the United States. The FDA has even issued explicit warnings about unauthorized smartwatches and rings marketed with glucose-monitoring claims, calling them potentially dangerous. What does exist are FDA-cleared continuous glucose monitors that sit under the skin, and an emerging ecosystem of smartwatches that can display data from those separate sensors.
What FDA-Cleared Glucose Monitors Actually Look Like
The glucose-monitoring devices that have earned FDA clearance all share one thing in common: they penetrate the skin. Continuous glucose monitors like the Dexcom G7 and FreeStyle Libre use a tiny filament inserted just below the skin’s surface to measure glucose in interstitial fluid, the liquid that surrounds your cells. This is not a watch you strap on and forget about. It is a small adhesive patch, usually worn on the upper arm or abdomen, with a sensor that stays in place for one to two weeks before replacement.
The FreeStyle Libre system, for instance, uses a sensor inserted under the skin to measure interstitial fluid glucose levels and transmits readings to a reader or smartphone app.1PubMed Central. Freestyle Libre Glucose Monitoring System These systems have been shown to meaningfully improve glucose control. In a trial comparing real-time continuous glucose monitoring against flash glucose monitoring in adults with type 1 diabetes, participants using real-time monitoring spent more time in their target glucose range after six months and had lower average blood sugar levels.2The Lancet. Effect of continuous glucose monitoring on glycemic control in adults with type 1 diabetes using insulin injections: the ALERTT1 trial These are proven, clinically validated devices. But they require a needle insertion, they leave a sensor stuck to your body, and they are medical devices with all the regulatory scrutiny that entails.
The accuracy standards for these devices are well established. Blood glucose monitors are evaluated against ISO 15197:2013 accuracy requirements, while continuous glucose monitors are assessed primarily by a metric called mean absolute relative difference, often supplemented by bias analysis and error grid analysis.3PubMed Central. Measures of Accuracy for Continuous Glucose Monitoring and Blood Glucose Monitoring Devices Any new glucose device, including a hypothetical glucose watch, would need to meet similarly rigorous benchmarks before the FDA would sign off.
Why a True Glucose Watch Does Not Exist Yet
The fundamental problem is physics. Glucose is a small molecule dissolved in your blood, and measuring it accurately without breaking the skin is extraordinarily difficult. Every approach researchers have tried runs into the same core issue: the signal from glucose is tiny compared to the noise from everything else happening in your body, including changes in temperature, hydration, skin thickness, blood flow, and movement.
There is also a physiological bottleneck. Even existing under-the-skin monitors do not measure blood glucose directly. They measure glucose in interstitial fluid, which lags behind blood glucose by about five to six minutes in healthy adults at rest.4PubMed Central. Time lag of glucose from intravascular to interstitial compartment in humans Separate work has estimated the physiological component of this lag at roughly five minutes, with additional delay introduced by the sensor hardware itself.5Diabetes Care. Physiological Differences Between Interstitial Glucose and Blood Glucose Measured in Human Subjects A wrist-worn device trying to read glucose through intact skin faces this same lag problem and then stacks additional technical delays on top of it. When someone’s blood sugar is crashing fast, even a few extra minutes of delay can mean the difference between catching a dangerous low and missing it entirely.
This is the reason that major technology companies, despite years of investment and some of the world’s best engineering talent, have not shipped a glucose-reading watch. The accuracy bar set by existing medical devices is high, and every noninvasive approach so far falls short of it in real-world conditions.
Optical Approaches Under Development
Several research groups are pursuing ways to shine light through the skin and detect glucose based on how the light interacts with tissue. The most prominent of these uses Raman spectroscopy, a technique that identifies molecules by the way they scatter laser light. Glucose has a distinctive molecular fingerprint under Raman scattering, and water interferes less with Raman signals than with some other optical methods, which is useful since human tissue is mostly water.6PubMed Central. Noninvasive Monitoring of Blood Glucose with Raman Spectroscopy
In one study of 111 hospitalized subjects, researchers using a custom Raman spectrometer system achieved noninvasive glucose measurements with average errors as low as 0.9 millimoles per liter. Accuracy varied by sex, with stronger correlations in male subjects than female subjects.7PubMed Central. Raman spectroscopy as a promising tool for noninvasive point-of-care glucose monitoring Those results are promising on paper, but the device was a laboratory instrument, not something you could strap to your wrist.
A persistent challenge with Raman-based glucose monitoring is calibration. The technique typically requires an extended calibration period lasting several weeks for each individual user. Recent work has attempted to shorten this by using a pre-trained calibration model that can be individualized through a brief phase of just ten measurements, which would make it more practical for everyday use.8Scientific Reports. Calibration and performance of a Raman-based device for non-invasive glucose monitoring in type 2 diabetes Even with this improvement, Raman systems remain bulky and power-hungry compared to what you would need in a watch.
Near-infrared spectroscopy is another optical method being explored. One research group developed a noninvasive system designed for the earlobe, taking advantage of that site’s thin skin and lack of bone or muscle. In a small pilot trial of five participants, the system achieved a mean absolute relative difference of about 5% for three subjects under stable conditions, and about 8% across all participants.9PubMed Central. Noninvasive Continuous Glucose Monitoring Using Multimodal Near-Infrared, Temperature, and Pressure Signals on the Earlobe Those accuracy numbers would be competitive with existing subcutaneous monitors if they held up in larger studies, but five people is far too few to draw conclusions, and the earlobe is a much more favorable measurement site than the wrist. The wrist has thicker skin, more variable blood flow, and more movement artifact, all of which degrade optical signals.
The Sweat-Based Approach and Its Problems
A different strategy skips light entirely and instead tries to measure glucose in sweat. Your sweat contains trace amounts of glucose, and if a sensor could reliably convert those concentrations into blood glucose estimates, it could theoretically be built into a watchband or patch. Researchers have developed prototype smartwatches that integrate microfluidic sweat collection with optical glucose sensors, using enzyme-based chemistry to generate signals proportional to sweat glucose concentration. On-body tests of one such system showed a statistically significant correlation with blood glucose levels within the physiological sweat glucose range.10PubMed. Microfluidic tesla valve sweat patch integrated smartwatch for optical continuous monitoring of glucose, oxygen, and heart rate
Another group built a wearable optical sensor watch using surface plasmon resonance technology with a nanostructured substrate designed to capture glucose in sweat and produce an optical signal. The prototype included wireless data transmission to a mobile app.11arXiv. Bridging Optical Sensing and Wearable Health Monitoring: A Functionalized Plasmonic Nanopillar for Non-Invasive Sweat Glucose Detection
The trouble is that the relationship between sweat glucose and blood glucose is not straightforward. During exercise, which is exactly when people tend to sweat enough for these sensors to work, the correlation between sweat and blood glucose concentrations is relatively poor.12PubMed Central. A wireless sweat sensing with a pH-based correlation model for continuous glucose monitoring and diabetes management during exercise Sweat rate varies enormously between individuals and even across different parts of the same person’s body. The amount of glucose in sweat depends on factors beyond blood sugar, including how fast you are sweating, local skin temperature, and how long the sweat sits on the skin before reaching the sensor.13PubMed Central. Comprehensive Review on Wearable Sweat-Glucose Sensors for Continuous Glucose Monitoring At rest, many people simply do not produce enough sweat for continuous monitoring. These limitations mean sweat-based glucose watches remain research prototypes, not clinical tools.
Smartwatches That Display CGM Data
While no watch can measure glucose on its own, several smartwatches can now display glucose readings from a separate continuous glucose monitor worn on the body. The Apple Watch, for example, can show real-time glucose data from a Dexcom CGM through a companion app. Some Android-compatible watches offer similar functionality. This integration has grown steadily as CGM systems have become more widely available, and their increasing connection with insulin pumps, watches, and smartphone applications reflects a broader trend toward connected diabetes management.14Archives of Medical Science. Continuous glucose monitoring (CGM) systems in Poland, Europe, and beyond in 2025: principles, available technologies, and future perspectives
This distinction matters because marketing language can be slippery. A smartwatch that “shows your glucose” is doing something genuinely useful: putting the data from a medical-grade sensor on your wrist where you can glance at it without pulling out your phone. But the watch itself is not measuring anything. The sensor under your skin is doing all the work. If the sensor is removed, the watch has no glucose data to display.
For people who already wear a CGM, having glucose trends visible on a watch face is a practical convenience. You can see your current reading and trend arrow during a meeting or a workout without any extra steps. Some setups also allow the watch to vibrate when glucose goes above or below a threshold, which can catch dangerous highs or lows faster than waiting for a phone notification. But none of this changes the underlying requirement: you still need a sensor stuck to your body.
Products Making Unverified Claims
The consumer desire for a glucose watch is so strong that products have appeared on online marketplaces claiming to offer noninvasive blood glucose monitoring through a smartwatch. The FDA has warned consumers not to use these devices. The agency’s concern is straightforward: if someone with diabetes relies on an inaccurate glucose reading from an unauthorized watch, they could take too much or too little insulin, leading to dangerously high or low blood sugar. These are not edge-case risks. Insulin dosing errors can be life-threatening.
The watches in question typically use photoplethysmography, the same green-light sensor technology that estimates heart rate. Some claim to derive glucose measurements from these optical heart-rate signals using proprietary algorithms. There is no published, peer-reviewed evidence that photoplethysmography at the wrist can reliably determine blood glucose concentration. The signal simply does not contain enough glucose-specific information to produce accurate readings. Independent testing of several of these products has shown that their glucose readings are essentially random relative to actual blood sugar levels.
If you encounter a watch on Amazon, AliExpress, or a similar marketplace that advertises blood glucose monitoring and costs under a few hundred dollars, it almost certainly falls into this category. The presence of glucose numbers on a screen does not mean those numbers are real. This is one area where the gap between what a product claims and what it can actually do has direct health consequences.
What the Big Tech Companies Are Doing
Apple has reportedly been working on noninvasive glucose sensing for over a decade, a project sometimes referred to internally as its most ambitious health initiative. Samsung and Google have also invested in the space. None of these companies have announced a timeline for a glucose-sensing watch, and the history of the field suggests that timelines are unreliable. Companies and startups have been promising noninvasive glucose monitors “within a few years” since the 1990s.
The technical barriers are not trivial engineering problems waiting for a clever solution. They are rooted in the physics of how light interacts with tissue and the biology of how glucose moves through the body. A wrist-worn device contends with variable skin pigmentation, subcutaneous fat thickness, wrist hair, tattoos, sensor-skin contact pressure, temperature changes, and motion artifacts from everyday activity. Each of these factors introduces noise that can swamp the tiny glucose signal. Even if you solved all of them in the lab, a consumer device needs to work reliably across millions of different wrists in every conceivable condition.
The most realistic near-term path may not be a fully noninvasive watch but rather a minimally invasive one. Some companies are working on microneedle arrays that could be built into a watch-like form factor, penetrating only the outermost layer of skin painlessly to reach interstitial fluid. This approach sidesteps the optical measurement problem entirely by directly accessing the fluid where glucose can be measured with proven electrochemical techniques. Whether consumers would consider a microneedle patch on the wrist to be meaningfully different from a CGM patch on the arm remains to be seen.
Insurance and Access Barriers for Existing Technology
While waiting for a glucose watch that may or may not arrive, existing continuous glucose monitors face their own adoption challenges. Coverage and reimbursement remain significant hurdles. Although CGMs are clinically meaningful additions to diabetes care, inadequate reimbursement of the clinicians’ time needed to train patients and interpret data has served as a barrier to broader adoption.15PubMed Central. The role of reimbursement in the adoption of continuous glucose monitors In the United States, CGM coverage varies by insurance plan, and many people with type 2 diabetes who could benefit from continuous monitoring do not have access to it.
This context matters when thinking about the glucose watch question. Part of the reason consumers are so eager for a glucose-sensing smartwatch is that existing CGMs remain expensive and require prescriptions in most countries. A watch that could bypass the medical supply chain and put glucose data on everyone’s wrist would be transformative. But the technical reality is that we are not close to that, and the products currently claiming to fill that gap are unreliable at best and dangerous at worst. For now, the most useful thing a smartwatch can do for glucose monitoring is serve as a convenient display for a real, FDA-cleared sensor doing the actual measurement underneath your skin.
The Earlobe, the Wrist, and Why Measurement Site Matters
One underappreciated factor in the glucose watch discussion is that the wrist is among the worst places on the human body to try noninvasive optical glucose measurement. The skin there is relatively thick and variable. There is significant bone and tendon very close to the surface, creating complex light-scattering patterns. Blood flow in the wrist is highly sensitive to temperature and position, meaning that raising or lowering your arm changes the optical environment the sensor is trying to read.
Researchers exploring other body sites have found markedly better results. The earlobe study mentioned earlier chose that location specifically because of its anatomical advantages: no bone, no muscle, and thin skin that allows better light transmission.9PubMed Central. Noninvasive Continuous Glucose Monitoring Using Multimodal Near-Infrared, Temperature, and Pressure Signals on the Earlobe The fingertip is another relatively favorable site, which is part of why traditional blood glucose meters use it. The lip, the tongue, and the eye have all been studied as potential measurement locations for noninvasive glucose sensing.
The watch form factor is driven by consumer preference, not by optical physics. People want glucose data on their wrist because that is where they already wear a device and glance at it throughout the day. But the body does not care about consumer preferences. If noninvasive glucose monitoring eventually works, it may arrive first as an earlobe clip, a ring, or an adhesive forehead patch before it ever makes its way into a wristwatch. The companies pursuing the watch form factor are essentially playing the game on hard mode because that is where the market demand is.