An initiative by Apple Inc. to include continuous, non-invasive blood glucose monitoring into the Apple watch is almost complete.

The project is purportedly known as E5.

E5 will be able to determine a person's blood glucose level without having to pierce the skin.

It has been stated that Apple uses optical absorption spectroscopy as a measuring technique and silicon photonics as a chip technology.

The device emits certain light wavelengths into a region beneath the skin using lasers.

Glucose may be taken from interstitial fluid, which is a liquid that circulates outside of veins and capillaries, below the skin.

 The light is reflected back to the sensor in a way that shows the glucose concentration.

The blood glucose level is then calculated using an algorithm.

It's yet unknown if Apple Inc. created this algorithm internally or outside.