In mid-July 2021 Patently Apple posted an IP report titled "Apple won a Major Patent for an 'Integrated Photonics Device' that could be used in a Future Apple Watch for Monitoring Blood Glucose+." The report noted that Apple was working with a UK Photonics company, known as Rockley, supplies specialized components for the smartwatch market. One medical network publication believes that Apple is working with this UK company on a blood glucose solution.

The Medical Device Network posted a report back in late May 2021 titled "Wearables and health tracking: Photonics could reinvent the Apple Watch." The report noted that "Rockley Photonics is thought to be developing technology that could allow the Apple Watch to non-invasively track blood glucose levels."

You could view a video on Rockley's technology here.  

Today, Bloomberg is reporting that Apple's glucose monitoring project  has hit major milestones are getting closer to this being a major feature for a future Apple Watch.

Roughly 1 in 10 Americans have diabetes, and they typically rely on a device that pokes the skin for a blood sample. There are also patches from Dexcom Inc. and Abbott Laboratories that are inserted into the skin but need to be replaced about every two weeks.

Just as the Rockley video presented above, Apple's solution is based on silicon photonics. The system uses lasers to emit specific wavelengths of light into an area below the skin where there is interstitial fluid — substances that leak out of capillaries — that can be absorbed by glucose. The light is then reflected back to the sensor in a way that indicates the concentration of glucose. An algorithm then determines a person’s blood glucose level.

Hundreds of engineers are working on the project as part of Apple’s Exploratory Design Group, or XDG, a previously unreported effort akin to X, the moonshot division of Alphabet Inc. It’s one of the most covert initiatives at the famously secretive Apple. Even fewer people are involved in it than the company’s self-driving car undertaking, overseen by the Special Projects Group, or the mixed-reality headset, which is being developed by its Technology Development Group.

For more on this, read the full Bloomberg report.

Apple has been working on this project for at minimum eight years. In August 2018 Patently Apple posted a patent report titled " One of the patents that the 'Secret Apple Team' was working on for Diabetes Testing for Apple Watch Surfaces." The patent, that actually dates back to 2015, covered "a non-invasive method of measuring things like glucose via Absorption spectroscopy."