Today, Circular becomes the first smart ring to offer continuous blood oxygen saturation (SpO2) monitoring throughout the entire night.

While pulse oximeters have existed for decades, no consumer smart ring has ever tracked SpO2 continuously during sleep, until now.

How it works. The Circular Ring uses red and infrared PPG sensors to measure oxygen saturation levels in your blood while you sleep. Every morning, you can see your average overnight SpO2, spot any drops, and track trends over time.

Where to find it. Your SpO2 data lives in the Sleep Analysis Circle within the Circular app. A clean graph shows your oxygen levels across the entire night, plotted against your sleep stages. Drops in SpO2 may indicate sleep-disordered breathing, giving you an early warning to discuss with your doctor.

With this update, the Circular Ring becomes the most complete sleep tracker available in a ring form factor: sleep stages, heart rate variability, respiratory rate, body temperature, and now continuous SpO2 — all from your finger.

Available today for all Circular Ring users. Update your app to access the new Sleep Analysis Circle.