Estimated oxygen variation (EOV) is an approximation of the changes in your blood oxygen saturation levels. Your blood oxygen saturation level is the percentage of your blood that’s saturated with, or contains, oxygen. Typically, your blood oxygen saturation level is between 95–100%, which means your blood is carrying as much oxygen as it can. The oxygen levels in your blood tend to remain relatively constant, even during exercise and sleep. If you stop breathing or have lung issues, your blood oxygen saturation level can fall as less oxygen enters your body (source).
EOV tracking is available on these devices:
- Fitbit Charge 3
- Fitbit Charge 4
- Fitbit Charge 5
- Fitbit Charge 6
- Fitbit Inspire 3
- Fitbit Luxe
- Fitbit Sense series
- Fitbit Versa series
- Google Pixel Watch series
Your device tracks your EOV while you sleep using red and infrared sensors on the back of the device. The sensors shine red and infrared light onto your skin and blood vessels, using the color of the light that bounces back to approximate how much oxygen is in your blood:
- Richly oxygenated blood is red and reflects more red light than infrared light.
- Poorly oxygenated blood is bluish red and reflects more infrared light than red light.
Wear your device to bed, and check your EOV graph in the morning in the Fitbit app. For instructions, see How do I see my estimated oxygen variation data in the Fitbit app?
- From the Today tab
in the Fitbit app, tap the Sleep duration tile then tap estimated oxygen variation.
in the Fitbit app, tap the Sleep duration tile then tap estimated oxygen variation.- To select other days:
Use the week, month, or year tabstap a sleep session
tap a sleep session Sync your Fitbit device each morning to see last night's sleep stats in the Fitbit app.
The estimated oxygen variation graph shows an estimate of the variations in your blood oxygen saturation levels throughout the night:
| Low variations show that your estimated blood oxygen saturation levels remained consistent. |
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| High variations show that your estimated blood oxygen saturation level fluctuated. A high variation on the graph may indicate you had variations or disturbances in your breathing during sleep. |
Consult your health care professional about any questions or health issues you may have.
Low variations in your estimated oxygen saturation levels are typical (source). Frequent high variations on your estimated oxygen variation graph may indicate that you experience breathing disturbances during sleep. Breathing disturbances can lead to higher than expected variations in blood oxygen levels, which can indicate that your body is not getting enough oxygen while you sleep. If you frequently see high variations on your graph, consider talking to your doctor, particularly if you experience symptoms such as excessive tiredness, loud snoring, or gasping during sleep.
Other factors, including your arm position and certain physical characteristics, can affect your estimated oxygen variation readings, making them appear to be more variable. Make sure your Fitbit device is snug and secure on your wrist. For more information, see How do I wear my Fitbit device?
If you move frequently during sleep, the movement can interfere with the light that bounces back to the sensors on your device.
To receive EOV data, note the following:
- Make sure your Fitbit device is snug and secure before you go to sleep. For more information, see How do I wear my Fitbit device?
- Make sure your Fitbit device is charged.
- You must have Charge 3, Charge 4, Charge 5, Charge 6, Inspire 3, Luxe, Sense series, Versa series, or a Google Pixel Watch series device.
- You must sleep 3 or more hours.