Apple Watch’s blood oxygen monitor is for ‘wellness,’ not medicine

Apple Watch’s blood oxygen(ˈäksəjən) monitor is for ‘wellness,’ not medicine

Wrist(rist)-based sensors usually aren’t as accurate(ˈakyərət) as fingertip(ˈfiNGɡərˌtip) devices

By Nicole Wetsman

The new Apple Watch Series(ˈsirēz) 6 includes a sensor that allows the watch to measure(ˈmeZHər) blood oxygen levels. The device is a long-awaited addition to Apple’s suite of health(helTH) tools, but it tracks oxygen levels at the wrist, which can be less accurate than measurements typically gathered at the fingertip.

Most oxygen sensors, including Apple’s, measure the amount of oxygen in your blood using light. These devices are called pulse(pəls) oximeters(äkˈsimidər), and they typically clip on to your fingertip. A standard version sends both red and infrared(ˌinfrəˈred) light through the finger, where there’s lots of blood close to the surface. A protein(ˈprōˌtēn) in the blood absorbs(əbˈzôrb) more infrared light when it has oxygen and more red light when it doesn’t. A sensor on the other side of the finger calculates how much of each type of light travels through, providing an oxygen reading.

The Apple Watch Series 6 also has red and infrared lights, but instead of sending that light through a body part, it measures the lights’ reflection. It’s the same strategy used by Garmin and Fitbit, which already have similar blood oxygen features(ˈfēCHər). But the reflective method at the wrist may be less accurate, especially when oxygen levels start to drop, according to some research.