Where to find the blood oxygen reading on your Apple Watch

The blood oxygen measurement appears in the Health app on your iPhone, not directly on the watch face itself. Open the Health app, tap the Browse tab at the bottom, select Respiratory, then tap Blood Oxygen. You will see your most recent reading and a history of measurements going back weeks or months depending on your watch model and watchOS version.

On the watch itself, you can add a blood oxygen complication to your watch face — a small widget that shows your current reading at a glance. Press and hold your watch face, tap Customize, scroll to find an empty slot, and add the Blood Oxygen complication. This lets you see the number without opening the Health app, though the actual measurement still happens through the watch's sensors.

Key Takeaways

  • Blood oxygen readings on Apple Watch appear in the Health app on your iPhone under Respiratory, not on the watch itself.
  • The watch measures automatically during sleep and when you hold your wrist still for 15 seconds during the day, so you do not need to start a measurement manually.
  • Series 6 and newer Apple Watches have the blood oxygen sensor; Series 3, 4, and 5 do not have this feature.
  • A reading between 95 and 100 percent is typical for most people at rest; readings below 90 percent warrant a conversation with your doctor.

How the Apple Watch measures blood oxygen

The Apple Watch uses red and infrared light to measure the amount of oxygen in your blood. The watch shines these lights through your skin and measures how much light bounces back. Blood with more oxygen absorbs light differently than blood with less oxygen, so the watch can calculate a percentage based on that difference.

The watch takes measurements automatically while you sleep, usually between midnight and 6 a.m. During waking hours, you can get a reading by holding your wrist still and keeping the watch face against your skin for about 15 seconds. The watch will vibrate when the measurement is complete. You do not need to open an app or press anything — just hold still.

Which Apple Watch models have blood oxygen

The blood oxygen sensor is built into Apple Watch Series 6 and later, including Series 7, Series 8, Series 9, and Ultra. If you own a Series 3, 4, or 5, your watch does not have this feature and cannot measure blood oxygen no matter what software version you install.

You can check your watch model by opening the Watch app on your iPhone, tapping General, then About. The model name appears at the top of the screen. If you see Series 6 or a higher number, you have the sensor.

Why your readings might be unavailable or inconsistent

Blood oxygen readings sometimes fail to record if your watch is not snug against your skin. A loose band, wet skin, or movement during measurement can prevent the sensor from getting a clear reading. Make sure your watch band is tight enough that you can fit only one finger underneath, and keep your wrist still while the measurement happens.

Readings may also be unavailable if you have a tattoo on your wrist where the watch sits. Dark ink can interfere with the light sensors. If this is your situation, try moving the watch higher up your arm or to your other wrist.

Cold hands and poor circulation can also make readings harder to get. If you are in a cold environment, warm your hands first. Some medications and medical conditions affect how easily the sensor can detect blood oxygen, so if readings are consistently unavailable, mention it to your doctor.

What your blood oxygen number actually means

A normal blood oxygen reading for most people at rest is between 95 and 100 percent. This means your lungs are moving oxygen into your blood effectively and your body is distributing it well. Readings in this range are healthy for most adults.

Readings between 90 and 94 percent are lower than ideal but not necessarily a sign of a problem on their own. However, if your readings consistently fall in this range or drop below 90 percent, contact your doctor. Low blood oxygen can indicate a respiratory issue, heart problem, or other condition that needs medical attention.

Keep in mind that Apple Watch readings are estimates, not medical-grade measurements. The watch is useful for spotting trends over time — for example, noticing that your readings drop when you are sick — but a single low reading should not alarm you. If you have concerns about your blood oxygen, your doctor can order a proper pulse oximeter or blood test for a definitive answer.

How to track blood oxygen trends over time

The Health app stores your blood oxygen history, so you can look back at weeks or months of readings to see whether your numbers are stable, improving, or declining. Open the Health app, go to Respiratory, tap Blood Oxygen, then scroll down to see a graph of your readings over time. You can change the view from Day to Week, Month, or Year by tapping the buttons at the top of the graph.

If you notice a pattern — for example, lower readings during certain seasons or after you start a new medication — write it down and mention it to your doctor. These trends can be more useful than any single reading. You can also share your Health data with your doctor if they use an app that connects to Apple Health, though you will need to set this up in the Health app first.

Troubleshooting when blood oxygen is not working

If the blood oxygen feature is not showing up in your Health app at all, first check that you are running the latest watchOS and iOS versions. Open the Watch app on your iPhone, go to General, then Software Update. Install any available updates and restart both devices.

Next, make sure blood oxygen tracking is turned on. In the Watch app on your iPhone, go to Privacy, scroll down to Blood Oxygen, and confirm that it is enabled. If it is already on, try turning it off, waiting 10 seconds, and turning it back on.

If readings are still not appearing after a manual measurement attempt, try restarting your watch. Press and hold the side button until the power-off slider appears, drag it to turn off the watch, wait 10 seconds, then press and hold the side button again to turn it back on. After the watch restarts, try taking a measurement again.

Frequently Asked Questions

Does Apple Watch blood oxygen work if I have dark skin?

Apple Watch blood oxygen readings are less reliable on people with darker skin tones because the light sensors have more difficulty reading through darker skin. If you are having trouble getting consistent readings, this may be why. The watch may still provide some data, but the accuracy is lower. Discuss your readings with your doctor rather than relying solely on the watch.

Can I check my blood oxygen while exercising?

The watch can measure blood oxygen during exercise, but the reading will be less accurate because movement interferes with the sensor. For the most reliable reading, take the measurement while sitting or lying down with your wrist still. If you want to see how your blood oxygen changes with activity, take a reading before you exercise and another one after you rest for a few minutes.

What does it mean if my blood oxygen drops at night?

A small drop in blood oxygen during sleep is normal — most people's readings dip slightly when they are lying down. However, if your readings consistently fall below 90 percent at night or drop sharply, it could indicate sleep apnea or another breathing issue. Talk to your doctor about your nighttime readings, especially if you also snore or wake up gasping for air.

Is the Apple Watch blood oxygen reading accurate enough to replace a doctor's test?

No. The Apple Watch is a consumer device, not a medical instrument. Its readings are estimates and can be off by several percentage points. If your doctor needs to know your blood oxygen level, they will use a medical-grade pulse oximeter or blood test. Use the watch to track trends and spot changes, but always confirm concerning readings with your doctor.