A breakthrough like this would be a boon to diabetics. Adding the monitoring system to the Apple Watch would make the device a coveted item for millions of diabetics around the world.

Apple uses a chip technology known as silicon photonics and a measurement process called optical absorption spectroscopy. 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 reflected back to the sensor in a way that indicates the concentration of glucose. An algorithm then determines a person’s blood glucose level.

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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 moon shot division of Alphabet.

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.

A representative for medical device company Abbott, meanwhile, said it’s also developing new glucose monitoring products. “Continued innovation in health tech is critical,” Abbott spokesman Scott Stoffel said. “It’s also complex and must be accurate, easy and affordable. Our FreeStyle Libre products address those needs.”

It has compared its own technology to standard tests on blood drawn from veins and samples taken from a prick in the skin, known as capillary blood.

Apple’s system – more than 12 years in the making – is now considered to be at a proof-of-concept stage. The company believes the technology is viable but needs to be shrunk down to a more practical size.

Engineers are working to develop a prototype device about the size of an iPhone that can be strapped to a person’s bicep. That would be a significant reduction from an early version of the system that sat on a table.

One of Apple’s goals for the technology is to create a preventive measure that warns people if they’re prediabetic. They then could make lifestyle changes to try to avoid developing Type 2 diabetes, which occurs when a person’s body doesn’t use insulin properly.

Apple’s regulatory team has already held early discussions about getting government approval for the system.

Numerous start-ups – and some of the world’s largest companies – have tried and failed to develop a non-invasive monitoring system. Others are still in trials; the GlucoRX multi-sensor non-invasive continuous glucose monitor – which uses radio frequencies – was unveiled at the Medica trade show in November 2022.

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Apple’s senior executives believe this problem is one that they’re uniquely positioned to crack, given the company’s expertise in hardware and software integration – along with its deep pockets.

The Apple Watch has gradually become more of a health tool. The first model, launched in 2015, included a heart-rate sensor but was more focused on fitness tracking. The device gained the ability to take electrocardiograms, or ECGs, from the wrist in 2018.

It also can now sense body temperature – for women’s health tracking – and calculate blood oxygen levels.