Apple Watch Blood Oxygen Is Back in the U.S.—But Not Fully on the Watch

Blood Oxygen monitoring already returned to affected U.S. Apple Watches on August 14, 2025. Apple restored the feature with iOS 18.6.1 and watchOS 11.6.1, but the U.S. version is redesigned: the Watch collects the optical sensor data, while the paired iPhone performs the final calculation and displays the result in the Health app.

That means the answer depends on what you mean by “returned.” The feature is available again, but the original experience—where the Watch itself calculated and displayed the result—has not returned on affected U.S. models. Apple has not announced a date for bringing that original on-Watch experience back.

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What “returned” means for Apple Watch Blood Oxygen

Apple’s U.S. Blood Oxygen feature now has two distinct implementations. Older supported watches and watches sold in regions unaffected by the U.S. patent dispute can use the original architecture. Certain newer U.S. watches use Apple’s workaround, in which the Watch gathers the signals and the iPhone analyzes them.

The most accurate summary is therefore: Blood Oxygen is back in the U.S., but on affected U.S. watches the sensor remains on the Watch while the result lives on the iPhone.

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Which Apple Watches received the U.S. restoration?

When Apple announced the restoration on August 14, 2025, it specifically named:

• Apple Watch Series 9
• Apple Watch Series 10
• Apple Watch Ultra 2

The announcement applied to U.S. units that had previously lacked Blood Oxygen because of the patent dispute. It did not change watches that already had the original feature, and it did not change Apple Watch units purchased outside the United States, according to Apple’s announcement.

Apple’s broader support documentation lists Blood Oxygen compatibility for Apple Watch Series 6 and later, excluding SE models, and all Apple Watch Ultra models. Current Apple models that list the feature include the Series 11 and Ultra 3. The Apple Watch SE line—including the current SE 3—does not have the Blood Oxygen sensor or app.

Compatibility is not determined by the generation name alone. Country or region, purchase date, and the watch’s part-number suffix can change the experience.

What does the LW/A suffix mean?

For U.S. Apple Watch models purchased on or after January 18, 2024, a part number ending in LW/A identifies the redesigned U.S. Blood Oxygen implementation in Apple’s support documentation.

On an affected LW/A watch:

• The Watch’s optical hardware records the relevant signals.
• The Watch sends processed signal data to the paired iPhone.
• The iPhone performs the final blood-oxygen analysis.
• The result is saved in the iPhone’s Health app.
• The result cannot be viewed directly on the Watch.

The suffix is more useful than simply asking whether a watch is a Series 9, Series 10, or Ultra 2. Two watches with the same generation name can have different Blood Oxygen behavior if they were sold in different markets or under different regional configurations.

How to check the part number

1. Open the Watch app on the paired iPhone.
2. Tap My Watch.
3. Tap General.
4. Tap About.
5. Find Model Number. It initially shows a part number beginning with “M.”
6. Check the part-number suffix for LW/A.

Tapping the model-number field reveals a separate five-digit model number beginning with “A.” For this issue, the relevant identifier is the part-number suffix, not merely the five-digit A-number. Apple’s identification instructions are available on its Apple Watch model identification page.

How Apple’s workaround works

Blood Oxygen measurements use photoplethysmography: the Watch shines red and infrared light into the skin, detects the reflected light, and uses those signals to estimate blood oxygen saturation.

For the redesigned U.S. implementation, the Watch still performs the optical sensing. The important change is where the final processing occurs. Documents reviewed by U.S. Customs and Border Protection describe the Watch emitting red and infrared light, detecting the reflected signals, and sending processed signal data to the iPhone. The iPhone then calculates the oxygen-saturation value. See CBP ruling H351038 and CBP ruling H338254.

The sensor is still in the Watch; the final calculation is not.

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This is why both of the following statements are misleading for affected U.S. LW/A watches:

• “The Blood Oxygen sensor was removed.”
• “Blood Oxygen is fully back on the Watch.”

The hardware remains capable of collecting the signal, but Apple moved the analysis and result display to the iPhone to support the redesigned product under the U.S. import-order dispute.

What update restored Blood Oxygen?

Affected owners needed:

• iOS 18.6.1 on the paired iPhone
• watchOS 11.6.1 on the Apple Watch

Those were the versions associated with Apple’s August 14, 2025 restoration announcement. Apple’s current instructions are to keep both devices on the latest compatible software, so a watch that has not been updated should not necessarily remain on those exact version numbers.

Update the iPhone first, then update the Watch through the Watch app or the Watch’s software-update settings. The watch must remain paired with the iPhone for the redesigned experience to be set up and used.

Where do you see the reading?

On an affected U.S. LW/A watch, the result is viewed on the iPhone at:

Health app → Search → Respiratory → Blood Oxygen

You may be able to start or be guided through the measurement on the Watch, but the completed result is not displayed directly on the Watch for these U.S. configurations. Apple’s Blood Oxygen instructions specifically direct users to the iPhone’s Health app for LW/A models.

Does Blood Oxygen work without the iPhone nearby?

Do not assume that it does.

The Watch can collect the optical signal, but Apple’s redesigned U.S. implementation requires the paired iPhone to perform the analysis and is designed to display the result in Health on that iPhone. Apple’s public instructions do not clearly specify every possible offline, delayed-sync, or out-of-range behavior for every watch and software combination.

The safe practical rule is: have the paired iPhone available and do not expect to obtain or view an analyzed reading independently on the Watch. Apple’s documentation confirms the location of the analysis and result, but it should not be stretched into a promise that every measurement will be processed offline or automatically appear later.

Are background measurements available?

Apple says the Blood Oxygen app can take periodic background measurements throughout the day when background measurements are enabled, in addition to readings started manually. Those measurements are saved in the Health app on the iPhone.

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There is an important limitation for affected U.S. LW/A watches: Apple’s current Vitals documentation says Blood Oxygen is not available in the Vitals app on U.S. units purchased on or after January 18, 2024 with the applicable LW/A configuration.

So these are not contradictory:

• Background Blood Oxygen measurements can be recorded and stored in Health.
• Blood Oxygen may not appear as an overnight metric inside Vitals on an affected U.S. LW/A watch.

If you are looking for a reading and do not see it in Vitals, check the Health app’s Respiratory section instead.

How to take a Blood Oxygen measurement

On a supported Apple Watch, Apple’s measurement process is:

1. Open Settings on the Apple Watch.
2. Tap Blood Oxygen.
3. Turn on Blood Oxygen Measurements.
4. Open the Blood Oxygen app.
5. Rest your arm on a table or in your lap.
6. Keep your wrist flat, with the Watch display facing upward.
7. Tap Start.
8. Hold your arm still during the 15-second countdown.
9. On an affected U.S. LW/A model, open the iPhone’s Health app after the measurement is processed.
10. Tap Search → Respiratory → Blood Oxygen to view the result.

Good fit matters. Apple says the Watch should have good skin contact and should be worn neither too tightly nor too loosely. Movement, poor contact, cold skin, tattoos, and other factors can interfere with an optical reading. The complete instructions are in Apple’s Measure blood oxygen levels guide.

Why was Blood Oxygen removed from U.S. Apple Watches?

The feature disappeared from newly sold affected U.S. watches because of a patent dispute between Apple and Masimo.

On October 26, 2023, the U.S. International Trade Commission found that Apple violated Section 337 in connection with Masimo patent claims and issued a limited exclusion order and cease-and-desist order. That created a U.S. import and sales problem for affected Apple Watch models.

Apple responded in stages. In January 2024, it sold certain U.S. watches with Blood Oxygen disabled rather than importing them with an active version of the original feature. Apple’s later workaround changed the product architecture by moving the final calculation from the Watch to the iPhone.

This article does not need to resolve every underlying patent allegation. The relevant practical facts are the agency findings and the way Apple changed the product to address the U.S. order.

The legal status after the redesign

The legal story has two separate tracks, and confusing them produces misleading headlines.

1. The original ITC patent ruling

On March 19, 2026, the U.S. Court of Appeals for the Federal Circuit affirmed the original ITC ruling that Apple had violated Masimo patents. That decision concerned the underlying patent dispute. It did not itself prohibit Apple’s redesigned Blood Oxygen implementation. Read the Federal Circuit opinion.

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2. The later challenge to Apple’s redesign

The ITC instituted a modification and enforcement proceeding in November 2025 concerning Apple’s redesigned products. On March 18, 2026, an administrative law judge found that the redesigned products did not infringe the asserted patents. On April 17, 2026, the ITC declined to review that finding, terminated the proceeding, and stated that the redesigned products should not be excluded under the existing limited exclusion order. See the ITC’s April 17 notice.

That April decision is the legal event most directly connected to whether the redesigned U.S. feature can remain available. It did not require Apple to move the calculation back onto the Watch.

The separate $634 million damages judgment

On July 20, 2026, a separate federal district-court case entered final judgment awarding Masimo $634,313,913 in patent damages. The judgment did not impose an injunction against Apple Watch sales or Blood Oxygen use. It therefore did not itself order Apple to disable the restored feature. The judgment is documented in the district-court final judgment.

In short, the damages ruling means the broader litigation remains financially significant. It does not mean Blood Oxygen was automatically removed again, and it does not establish a public date for restoring the original on-Watch calculation.

Which models support Blood Oxygen now?

Apple’s Apple Watch model documentation, Series 11 product page, and Ultra 3 product page provide the current model information. Regional availability and the U.S. LW/A qualification still matter even when a model generation is listed as compatible.

What to do if Blood Oxygen is missing

Work through this checklist before assuming that the sensor is defective or that another patent-related change has occurred:

1. Check the model. Apple Watch SE models do not support Blood Oxygen. A compatible watch is generally Series 6 or later, excluding SE, or an Ultra model.
2. Check the market. Blood Oxygen availability varies by region. The U.S. workaround does not mean every country uses the same implementation.
3. Update both devices. Install the latest compatible iOS on the paired iPhone and watchOS on the Watch. The original restoration used iOS 18.6.1 and watchOS 11.6.1.
4. Confirm pairing. The redesigned U.S. feature depends on the paired iPhone for analysis and result display.
5. Look for the app on the Watch. If Blood Oxygen is supported and enabled, the Blood Oxygen app should be available on the Watch.
6. Check the correct iPhone location. Go to Health → Search → Respiratory → Blood Oxygen, not just the Watch’s Vitals app.
7. Check the part number. For U.S. watches purchased on or after January 18, 2024, check whether the part number ends in LW/A.
8. Check the user’s age. Apple says the Blood Oxygen app is unavailable to people under 18.
9. Check fit and contact. Wear the Watch with good skin contact, not too tight or too loose, and keep the arm still for the 15-second reading.

Apple does not provide a separate consumer-facing “restore Blood Oxygen” switch. If the model, region, software, pairing, and setup are correct but the app or Health category is still missing, Apple Support is the appropriate next step.

Should you buy an Apple Watch for Blood Oxygen?

Buy one for this feature only if you are comfortable with the version your region provides.

A U.S. buyer considering a newer Series 9, Series 10, Ultra 2, Series 11, or Ultra 3 should expect the practical trade-offs of the redesigned experience:

• The Watch collects the optical data, but the iPhone performs the final analysis.
• The result is viewed in Health rather than directly on the Watch.
• Blood Oxygen is not available in Vitals on affected U.S. LW/A models.
• The paired iPhone is part of the analysis and viewing workflow.
• An Apple Watch SE is not an option if Blood Oxygen is important.

An older U.S. watch that already had the original feature may offer the on-Watch experience, but used-watch buyers should verify the exact model, condition, region, and part number rather than relying on the generation name alone. A non-U.S. watch may retain the original regional experience, but importing a watch does not make regional restrictions or compatibility questions disappear.

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Most importantly, Blood Oxygen on Apple Watch is a wellness feature. Apple says the measurements are intended for general fitness and wellness and are not intended for medical use or self-diagnosis. It should not replace a medical pulse oximeter, a clinician’s assessment, or urgent medical care when symptoms are present. See Apple’s Blood Oxygen support documentation for the applicable disclaimer.

Will the original on-Watch experience return?

There is no publicly announced date for Apple to restore the original calculation and display experience on affected U.S. LW/A watches.

The April 17, 2026 ITC decision removed the immediate exclusion-order threat to Apple’s redesigned products, but it did not require Apple to change the architecture again. Apple’s current support documentation continues to describe U.S. LW/A watches as sending Blood Oxygen data to the iPhone for analysis.

For now, the sensible expectation is that the redesigned feature is the U.S. solution: Blood Oxygen is available again, but the iPhone remains responsible for the result.

Blood Oxygen return timeline

Frequently Asked Questions

Is Blood Oxygen back on the Apple Watch in the U.S.?

Yes. Apple restored Blood Oxygen on affected U.S. Apple Watch units on August 14, 2025, through iOS 18.6.1 and watchOS 11.6.1. However, affected U.S. models use the iPhone to calculate and display the result.

Can I see Blood Oxygen directly on an affected U.S. Apple Watch?

No. On affected U.S. models with a part number ending in LW/A, the Watch collects the sensor data but the paired iPhone performs the analysis. View the result in Health → Search → Respiratory → Blood Oxygen.

Does Apple Watch SE have Blood Oxygen?

No. Apple Watch SE models, including SE 3, do not support the Blood Oxygen app or sensor.

Why is Blood Oxygen missing from Vitals?

Apple says Blood Oxygen is unavailable in the Vitals app on affected U.S. LW/A models purchased on or after January 18, 2024. Check the iPhone’s Health app under Search → Respiratory → Blood Oxygen instead.

Will the original on-Watch Blood Oxygen experience return?

Apple has not announced a date for restoring the original fully on-Watch calculation and display experience on affected U.S. LW/A models.

The Bottom Line

Bottom line: Blood Oxygen has already returned to affected U.S. Apple Watches, but not in its original form. On LW/A models, the Watch senses and records the data while the paired iPhone calculates the result and stores it in Health. There is currently no announced date for bringing the calculation and result back onto the Watch itself.

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