Apple Watch tipped for game-changing blood glucose tracking — how it could work

Apple Watch Series 8 sensors
(Image credit: Tom's Guide)

According to a Bloomberg report, technology that would outfit the Apple Watch with a non-invasive blood glucose-reading sensor is in the works and "hitting major milestones."

Rumors of a blood glucose sensor joining the other health tech inside Apple's smartwatch (including the ECG reader currently being contested through the ITC for copyright infringement) started before the Apple Watch Series 7 launch. But we saw conflicting reports about how much progress was being made on the system.

Now, Bloomberg's Mark Gurman unnamed sources say "the technology is viable" based on the company's testing. The project is still in the "proof-of-concept stage" but the next major challenge would be fitting the technology into the Apple Watch's small design.

Gurman's sources say the prototype device is approximately the size of an iPhone and is meant to be worn around a bicep. Unlike the finger-pricking blood glucose testing systems you might think of, this device allegedly uses non-invasive lasers to read glucose concentrations.

How it could work

Apple Is reportedly pairing silicon photonics with measurement system called optical absorption spectroscopy. Non-invasive lasers emit light that gets absorbed by the glucose within interstitial fluid, and the amount of light reflected back to the device can be used to determine that body's blood glucose level.

The concept isn't all that different from how the Apple Watch collects heart rate and SpO2 readings. But it would seem accurately reading glucose levels requires more sophisticated technology. Apparently Apple has tested its version of the glucose technology on "hundreds of people" already, yet there is "still years of work ahead" to bring it to market.

Analysis: Why this is a big deal

CDC’s National Diabetes Statistics Report in 2020 found that 34.2 million Americans — practically 1 in 10 — have diabetes. Meanwhile, about 1 in 3 American adults have prediabetes. 

That’s a significant population that would immediately benefit from a smartwatch sensor designed to read blood sugar levels when traditional testing methods might not be available. Apple hopes it could even even act as a "preventative measure that warns people if they’re prediabetic."

Diabetic users with certain blood glucose monitor systems can use the Apple Watch to check glucose levels conveniently from their wrist. Still, there’s a catch — you need your smartphone for Apple Watch monitoring to work. You can’t use your Apple Watch to get glucose readings from an on-body insulin pump when your iPhone is dead or out of Bluetooth reach, since data from monitoring systems are tied to companion smartphone apps.

Will the Apple Watch Series 9 have blood glucose monitoring? 

It’s important to note that such a smartwatch feature probably couldn't replace all invasive tests. Even if it works well and provides convenience, there are other concerns at play, including how an additional Apple Watch health sensor would impact price and battery life. 

While the addition of a skin temperature reader didn't bring any changes of that nature to the Apple Watch Series 8, blood glucose monitoring would likely have greater repercussions. The way I see it, the modern Apple Watch toes the line of medical device. The addition of glucose readings could transform the smartwatch into an essential health-monitoring tool.

Based on the Bloomberg report, the Apple Watch Series 9 will not be the watch that changes the game, and neither might the flagships for the next few years to come. Perhaps the Apple Watch Ultra 2 will be large enough to fit all the necessary technology.

Kate Kozuch

Kate Kozuch is the managing editor of social and video at Tom’s Guide. She covers smartwatches, TVs and audio devices, too. Kate appears on Fox News to talk tech trends and runs the Tom's Guide TikTok account, which you should be following. When she’s not filming tech videos, you can find her taking up a new sport, mastering the NYT Crossword or channeling her inner celebrity chef.