No Apple Watch, smartwatch or smart ring can measure blood sugar on its own, but a watch can show readings from a CGM sensor worn under the skin. Here is what the FDA and Health Canada say, how a CGM measures glucose, why needle-free sensing is so hard, and what a watch can do for diabetes.
No. No Apple Watch, and no other smartwatch or smart ring, can measure blood sugar on its own. The US Food and Drug Administration (FDA) says it has not authorized, cleared or approved any smartwatch or smart ring intended to measure or estimate blood glucose values on its own, and Health Canada says it has not authorized any smartwatch that can independently monitor blood glucose levels 1, 2. What a watch can do is display readings from a continuous glucose monitor (CGM), a device with a small sensor that pierces the skin 1.
Watches and rings that claim to read glucose without a needle are still widely advertised. The FDA says they are made by dozens of companies, sold under multiple brand names and offered through online marketplaces or directly by sellers 1. Health Canada says social media and online retail platforms are promoting unauthorized glucose-reading smartwatches 2.
This article covers what the FDA and Health Canada have said and when, how a CGM actually measures glucose and why its readings run a few minutes behind your blood, what an Apple Watch can usefully do for people with diabetes, and why measuring glucose through the skin is so hard.
No smartwatch or smart ring is authorized to measure blood sugar on its own in the United States or Canada. On February 21, 2024, the FDA warned consumers, patients, caregivers and health care providers about smartwatches and smart rings that claim to measure blood glucose without piercing the skin 1. It stated: “The FDA has not authorized, cleared, or approved any smartwatch or smart ring that is intended to measure or estimate blood glucose values on its own” 1.
The FDA separates these products from smartwatch apps that display data from FDA-authorized glucose devices that pierce the skin, such as CGMs 1. Its advice to consumers is direct: “Do not buy or use smartwatches or smart rings that claim to measure blood glucose levels.” It adds that their safety and effectiveness have not been reviewed by the FDA, and that people whose care depends on accurate glucose readings should talk to their health care provider about an FDA-authorized device 1.
Health Canada reached the same position first. Its November 2023 advisory says the smartwatches being promoted have not been assessed for safety and effectiveness, and may give false readings or fail to give timely alerts 2. In June 2025 it went further: “Health Canada has not authorized the sale of any non-invasive blood glucose monitoring devices.” It adds that some of these products claim to measure glucose without puncturing the skin, and that some promotional material falsely uses Health Canada’s corporate signature 3. Health Canada advises using only glucose devices listed in its Medical Devices Active Licence Listing (MDALL) 2, 3.
| Date | Regulator | What it said |
|---|---|---|
| November 29, 2023 | Health Canada | “Health Canada has not authorized any smartwatches that can independently monitor blood glucose levels” 2 |
| February 21, 2024 | US FDA | Has not authorized, cleared or approved any smartwatch or smart ring intended to measure or estimate blood glucose values on its own 1 |
| February 26, 2024 | US FDA | Cleared a Dexcom G7 change that displays glucose data directly from the transmitter on compatible iOS smartwatches 4 |
| March 19, 2025 | Health Canada | CGM safety alerts on smart devices, such as smartphones or smartwatches, may not work as expected 8 |
| June 27, 2025 | Health Canada | “Health Canada has not authorized the sale of any non-invasive blood glucose monitoring devices” 3 |
These statements carry dates, so the regulators’ own pages and Health Canada’s licence listing are the places to check for changes.
A CGM measures glucose in interstitial fluid, the fluid between your cells, through a small sensor that sits just under the skin 5, 9. You insert the sensor, usually on the belly or arm, and it uses a needle to pierce the skin 5. A tiny electrode beneath the skin then derives glucose values from the surrounding fluid 6. The FDA’s 510(k) summary for the Dexcom G7, for example, describes a wire-type sensor that continuously measures interstitial glucose, reports new data every 5 minutes and is worn for up to 10 days 4.
A transmitter sends the readings without wires to an app on a smartphone, to an insulin pump or to a separate receiver 9. Some CGMs need an occasional finger-stick check to calibrate the system 9, while the Dexcom G7 is cleared for people 2 years and older and is intended to replace finger-stick testing for diabetes treatment decisions 4.
In May 2024, Cleveland Clinic noted that one CGM was available over the counter, and that over-the-counter CGMs may not suit people who use insulin or who have significant low blood sugar episodes 5. The American Diabetes Association (ADA) notes that over-the-counter CGM lacks alarms and alerts 10. For a side-by-side look at the two main tools, see CGM vs blood glucose meter.
In plain terms: A meter reads a drop of blood from your fingertip. A CGM reads the fluid just under your skin, through a sensor that stays in place for days. A watch paired with a CGM shows the sensor’s numbers; the measuring happens in the sensor.
Typically 5 to 10 minutes, because glucose reaches the bloodstream first and then moves into the fluid under the skin 5, 6. In a Mayo Clinic study of eight healthy adults, researchers gave a glucose tracer into a vein and sampled the fluid under the skin of the belly. The tracer took 5.3 to 6.2 minutes on average to arrive 11. The authors concluded that this delay should not seriously compromise the accuracy of glucose sensors in the fasting state 11.
The lag matters most when glucose is moving quickly. The ADA’s 2026 Standards of Care say interstitial glucose correlates well with blood glucose but can lag when levels are rising or falling rapidly 10. A review in the Cleveland Clinic Journal of Medicine adds that all CGM sensors are known to be less accurate when glucose is low 6. Some substances can also affect readings, and Cleveland Clinic lists acetaminophen, hydroxyurea and vitamin C 5.
For these reasons, the ADA says everyone using a CGM must also have access to a blood glucose meter at all times 10. It describes using a meter to confirm accuracy when a sensor reading doesn’t fit how you feel, whenever the CGM is suspected of being inaccurate, while a new sensor warms up, when the CGM’s transmission is disrupted, and when glucose is changing rapidly 10.
It can put the readings from a cleared CGM on your wrist, and it can record activity and heart rate, which matter for glucose and for heart health 12. The glucose number itself still comes from the sensor under your skin 1, 5.
Health Canada notes that people can use authorized devices inserted under the skin with a smartwatch or smartphone to monitor blood glucose 2, and Cleveland Clinic lists the smartwatch among the devices that can display CGM data, along with a smartphone, an insulin pump or a handheld device 5. Some systems can also skip the phone: in February 2024 the FDA cleared a change to the Dexcom G7 that lets users display glucose data directly from the transmitter on compatible iOS smartwatches, a feature called Direct to Watch 4.
Alerts deserve a check. In March 2025, Health Canada warned that CGM safety alerts on smartphones or smartwatches may not work as expected: focus or do-not-disturb modes, Bluetooth, operating system updates and battery-saving features can stop an alert from being heard, and a missed alert can mean a low or high goes untreated 8. It advises checking your alert settings against your device’s manual and, if you feel unwell, checking your glucose “using your continuous glucose monitor or an alternative method” and seeking medical attention if necessary 8.
Diabetes Canada recommends that people with diabetes accumulate at least 150 minutes a week of moderate- to vigorous-intensity aerobic exercise, plus resistance exercise at least twice a week. It notes that a step monitor, such as a pedometer or accelerometer, can help you track your activity 13.
An activity record is most useful next to your glucose, because exercise can move it in both directions. Mayo Clinic notes that exercise can make blood sugar fall too low in people who take insulin, that a low can happen even 4 to 8 hours after exercise, and that strength training and high-intensity interval training may raise blood sugar 14. Diabetes Canada adds that prolonged aerobic exercise increases insulin sensitivity for up to 48 hours afterward, and that in type 1 diabetes, exercise late in the day or in the evening can raise the risk of a low overnight 13. Our article on exercise and glucose covers these patterns in more detail.
Treat a watch’s calorie count with caution. In a 2017 Stanford study, 60 volunteers wore seven wrist devices, including the Apple Watch, while walking, running or cycling. None measured energy expenditure accurately: the most accurate was off by an average of 27%, and the least accurate by 93% 12.
Heart rate is a different story. In the same Stanford study, six of the seven devices measured heart rate with an error of less than 5% 12. In the Stanford-led Apple Heart Study of 419,297 people, 0.52% received an irregular pulse notification. Among notified participants who returned an electrocardiogram (ECG) patch with usable data, 34% had atrial fibrillation, an irregular heart rhythm 15.
Sleep affects glucose too. In a study from Leiden University Medical Center of nine healthy adults, one night of about 4 hours of sleep made insulin work less well. The rate at which their bodies cleared glucose under insulin fell by about a fifth, and their own glucose production rose 16. The authors concluded that partial sleep loss on a single night causes insulin resistance in several metabolic pathways 16. See how sleep affects glucose.
Because a device resting on the skin has to detect glucose without touching blood or the fluid beneath, and researchers have struggled even to show that the signals they read come from glucose 7. The tools that are authorized reach the fluid itself: a meter tests blood from a fingertip, and a CGM places a sensor under the skin 6, 17. The FDA describes authorized glucose devices such as CGMs as ones that pierce the skin 1.
Raman spectroscopy shows the problem. It is a light-based method valued for its molecular specificity, its ability to tell one molecule from another, and it had been investigated for glucose sensing for about a decade 7. Earlier studies reported glucose sensing based on indirect evidence, such as a statistical correlation with reference glucose values, but failed to show glucose’s own Raman peaks, which raised questions about whether the method works for glucose 7. In 2020, a team from MIT and Samsung reported the first direct observation of glucose Raman peaks from living skin, in experiments in three pigs whose glucose was held at set levels. The signal rose and fell in proportion to reference glucose 7. The authors wrote that the finding may quiet the long debate about whether glucose Raman spectra can be measured through the skin 7. It was an animal study, not a device.
Many products are trying. A 2022 review of glucose monitors that avoid drawing blood, limited to products with regulatory clearance or significant news coverage since 2016, counted 28 noninvasive optical products, 6 noninvasive fluid sampling products and 31 minimally invasive products 17. The authors discussed the barriers ahead, both technical and non-technical 17. As of Health Canada’s June 2025 statement, no non-invasive blood glucose monitor had been authorized for sale in Canada 3.
Other research estimates glucose from what a watch already records. A Duke University team paired about 25,000 smartwatch measurements with simultaneous interstitial glucose readings and food logs over 10 days, and its best models predicted interstitial glucose with up to 87% accuracy by the study’s own measure 18. An estimate like this is learned from glucose readings; it is not a measurement of glucose.
No. The FDA warns that for people with diabetes, inaccurate blood glucose measurements can lead to errors in diabetes management, including taking the wrong dose of insulin, sulfonylureas or other medicines that can rapidly lower blood glucose 1. In its words, “Taking too much of these medications can quickly lead to dangerously low glucose, leading to mental confusion, coma, or death within hours of the error” 1.
Health Canada describes both directions of the risk. If a false reading is used to make treatment decisions, a person could take too little insulin, which can lead to high blood sugar, or too much, which can lead to low blood sugar, with possible loss of consciousness, seizure, coma and death 2. It advises against using glucose-reading smartwatches it has not authorized, and asks people to report problems with health products 2.
Even cleared CGMs come with safeguards. The ADA says everyone using a CGM must have access to a meter at all times and should confirm readings that don’t fit how they feel 10, and CGM sensors are less accurate when glucose is low 6. A device that has never been assessed for safety and effectiveness offers none of that assurance 2. Our guide to low blood sugar covers the warning signs, and how to choose a diabetes app explains what to look for in software that shows your readings.
Yes, if you use a CGM. In 2024 the FDA cleared a Dexcom G7 feature that shows glucose directly on compatible iOS smartwatches 4. The reading still comes from the sensor under your skin 5.
No. In its February 21, 2024 safety communication, the FDA said it had not authorized, cleared or approved any smartwatch or smart ring intended to measure or estimate blood glucose values on its own 1. Health Canada has said the same of smartwatches in Canada 2.
No. The FDA’s 2024 warning covers smart rings as well as smartwatches that claim to measure glucose without piercing the skin 1. In Canada, Health Canada has not authorized the sale of any non-invasive blood glucose monitoring device 3.
Typically 5 to 10 minutes 6. In a Mayo Clinic study of healthy adults, glucose took 5.3 to 6.2 minutes on average to move from the blood into the fluid under the skin 11. The gap matters most when glucose is rising or falling quickly 10.
Sometimes. Some CGMs need finger sticks to calibrate 9, while others, such as the Dexcom G7, are cleared to replace finger-stick testing for treatment decisions 4. Either way, the ADA says people using a CGM must also have access to a blood glucose meter at all times, for example to confirm readings that don’t fit how they feel 10.
Glyve’s Apple Watch app and widgets show your recent readings and logs, and they can sit on the watch face and the Lock Screen. The glucose comes from Apple Health, where most CGM apps write readings, from Dexcom and FreeStyle Libre through your own Dexcom Share or LibreLinkUp follower account, or from meter readings you type in. Readings from a follower account can arrive later than in your CGM’s own app, and a CGM is not required. On one timeline you can log food, insulin, exercise, sleep and stress by typing, by voice or with a photo, and every estimate is a draft you check before saving. The day view shows your glucose against the target range you set, and the week view shows whether a pattern after evening exercise or a short night repeats. Glyve is not a medical device: it gives no medical advice, sends no glucose alarms and does not replace your CGM’s own alerts or your care team.
How we write about diabetes. Spotted a mistake? Email info@glyve.ca and we’ll check it against the source.
Glyve keeps glucose, food, insulin, exercise, sleep and stress on one timeline.
For iPhone, iPad and Apple Watch.