Skip to main content

4.0 Sensor Feature: Measuring Blood Oxygen Levels (SPO2)

WHOOP 4.0 now measures blood oxygen levels (SPO2), viewable through the Health Monitor.

How WHOOP measures Blood Oxygen 

Using infrared, red LEDs and an advanced algorithm, WHOOP 4.0's pulse oximeter is capable of calculating a member's blood oxygen levels. Pulse oximetry is the measure of the amount of oxygen carried in the blood, to determine how well your heart is pumping that oxygen throughout the body. 


  • Measured during sleep, averaged across sleep time. 


  • SPO2 has a standardized range: 90-100%. (WHOOP does not use a personalized range). 
  • Taken with two new LEDs (red and IR LED). 
green alert = 90% and above.
orange alert = 89% or below.


  • Recovery score is a function of HRV, RR, sleep performance, and the metrics used to predict illness (such as RR, SpO2, and Skin temp). 

Example of Low SPO2 messaging: 

Your blood oxygen level of XX% was abnormally low last night. If you are currently in a high altitude location a decrease in blood oxygen is expected. If that is not the case, consider monitoring this metric over the next few days.

NOTE: There is no elevated/high SPO2 messaging because it would be virtually impossible, as blood oxygen can't rise above 100%. 

My SPO2 is in a 'recalibrating' state. What does that mean?

SpO2 sampling requires a clean signal and is taken with red and IR LEDs that are turned on intermittently during sleep or very low motion. Unlike other products, to keep the integrity of the measurement we do not report any values calculated that are doubtful or unreliable.

So, every sample must have clean signal quality with high confidence or will be discarded. In the event that there are no readings with high confidence, your device will enter recalibration mode. Some steps to take to ensure clean signal quality are making sure strap tightness is correct and ensuring that the sleep’s bounds are correct. Shorter periods of sleep will by nature have a higher likelihood of falling into this state.

After you enter a 'recalibrating' state, it is expected that your SPO2 reading will be available on proceeding nights.

If you enter this 'recalibrating' state for more than one night in a row, please contact Membership Services.



Related Articles: 4.0 Feature: Measuring Skin Temperature 

  • Was this article helpful?