Apple’s Blood Oxygen Workaround Sparked a Masimo Lawsuit—Here’s What Happened Next

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Apple restored Blood Oxygen readings on certain U.S. Apple Watch models by moving the analysis from the watch to the paired iPhone. Masimo sued U.S. Customs and Border Protection (CBP) on August 20, 2025, arguing that the agency improperly approved Apple’s redesigned watches. But the later legal result was more nuanced: the Federal Circuit upheld the ruling against Apple’s original on-watch implementation, while the ITC determined on April 17, 2026, that Apple’s second, iPhone-calculated redesign did not violate the exclusion order.

As of August 16, 2026, the original implementation remains barred from U.S. importation, while the redesigned version remains available subject to any further legal review.

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The short version for Apple Watch owners

• Original Blood Oxygen implementation: the watch processed and displayed the result, and the Federal Circuit upheld the ITC’s infringement ruling against it.
• Apple’s redesign: the watch still collects sensor data, but the paired iPhone performs the analysis and calculation. Results appear in the iPhone Health app, not directly on the affected watch.
• Masimo’s lawsuit: Masimo challenged CBP and government officials over approval of the redesign. It was not simply a new direct patent-infringement lawsuit against Apple.
• Latest enforcement result: on April 17, 2026, the ITC found that the second redesign did not violate the exclusion order.

That means the headline’s “fresh lawsuit” describes an important 2025 development, but not the final current picture.

Why Apple disabled Blood Oxygen in the U.S.

Apple introduced Blood Oxygen with the Apple Watch Series 6 in September 2020. The feature uses light-emitting diodes and photodiodes to collect information related to blood oxygen saturation. In Apple’s original implementation, the watch’s own system processed the measurement and presented the result.

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Masimo filed an ITC complaint in June 2021, alleging that Apple Watch models infringed patents covering wearable blood-oxygen measurement technology. The ITC found infringement and issued a limited exclusion order restricting the importation of infringing Apple Watches into the United States. Apple subsequently sold certain U.S. watches with Blood Oxygen disabled.

The hardware sensor was not necessarily removed. The key issue was how the feature operated and whether the implementation fell within the patents and the ITC’s exclusion order. Apple Watch SE models were not part of this feature dispute because Blood Oxygen was not supported on the SE.

Timeline of the Apple-Masimo dispute

What Apple changed technically

Apple’s public description points to a change in the processing path rather than the removal of the watch’s sensing hardware:

Original implementation: watch sensor → watch processing → result on the watch and in Health.

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Redesigned U.S. implementation: watch sensor → paired iPhone processing → result in the iPhone Health app.

In practical terms, the user still starts the reading on the watch. The watch collects the relevant sensor data, but the paired iPhone calculates the Blood Oxygen result. Apple introduced this official redesign through iOS 18.6.1 and watchOS 11.6.1. It is not an unofficial hack or a third-party workaround.

How the redesigned reading works

1. Wear the Apple Watch snugly but comfortably.
2. Open the Blood Oxygen app on the watch.
3. Keep the wrist flat with the watch facing upward.
4. Tap Start.
5. Keep the arm still for about 15 seconds.
6. Open the Health app on the paired iPhone.
7. Go to Search → Respiratory → Blood Oxygen to view the result.

On affected U.S. units, the number does not appear directly on the watch in the redesigned experience. That makes the paired iPhone part of the feature’s practical workflow.

Why Masimo sued CBP

Masimo alleged that CBP had effectively created a loophole around the ITC’s exclusion order. Its complaint argued that CBP’s role was to enforce the order, not approve a redesign that allegedly preserved the substance of the prohibited Blood Oxygen functionality while changing where processing occurred.

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Masimo filed the action in the U.S. District Court for the District of Columbia on August 20, 2025, naming CBP and certain government officials. It sought emergency relief, including a temporary restraining order and preliminary injunction. Masimo also asked the ITC to clarify or modify the exclusion order so it would cover Apple’s second redesign.

Those were Masimo’s allegations—not a final judicial finding. The distinction matters because the later ITC enforcement proceeding reached a result favorable to Apple’s redesigned implementation.

What the later rulings mean

The Federal Circuit: Apple lost on the original implementation

On March 19, 2026, the Federal Circuit affirmed the original ITC decision. The ruling upheld the ITC’s findings concerning infringement, patent validity, and domestic industry. In other words, Apple did not overturn the exclusion order by appealing the original case.

The ITC enforcement proceeding: Apple prevailed on the second redesign

The ITC opened a combined enforcement and modification proceeding on November 14, 2025. After an evidentiary hearing on January 28, 2026, the Commission issued its final enforcement determination on April 17, 2026, finding that Apple did not violate the exclusion order through the second redesign.

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These outcomes are not contradictory. They concern different implementations and different legal questions:

Masimo’s D.C. lawsuit should not be described as automatically stopping Apple’s workaround. The available filing confirms the ITC result, but it does not establish the final procedural disposition of the D.C. action. It is therefore more accurate to say that Masimo challenged the government’s approval while the redesigned implementation later survived the ITC enforcement proceeding.

Which Apple Watches are affected?

Apple says the redesigned U.S. experience applies to certain Apple Watch Series 9, Series 10, and Apple Watch Ultra 2 units that originally shipped without the Blood Oxygen feature. The paired iPhone must run iOS 18.6.1 or later and the watch must run watchOS 11.6.1 or later, subject to Apple’s compatibility requirements.

Apple’s announcement specifically identifies U.S. models purchased on or after January 18, 2024, with part numbers ending in LW/A. On those units, Blood Oxygen analysis is performed on the iPhone and results are viewed in Health.

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Eligibility is not automatic for every Series 9, Series 10, or Ultra 2. It depends on:

• the watch’s region and model configuration;
• the purchase date and part number;
• the software installed on both devices; and
• whether the watch already had the original Blood Oxygen feature.

Apple says the redesigned experience does not apply to watches that already had the original feature or to watches purchased outside the U.S. Previously purchased U.S. watches that already included the original feature were treated differently from newly sold or serviced units subject to the post-ban configuration.

Troubleshooting the iPhone-based feature

If a reading does not work, check the following:

• Software: update the iPhone and Apple Watch to the required versions or later.
• Model: confirm that the watch is an eligible Series 9, Series 10, or Ultra 2 configuration. Apple Watch SE does not support Blood Oxygen.
• Region: verify that the watch was sold for the U.S. market. International models may follow different rules.
• Pairing: keep the watch paired with the correct iPhone and allow time for synchronization.
• Fit: tighten the band enough for good skin contact without making it uncomfortable.
• Movement: keep the wrist and arm still during the approximately 15-second measurement.
• App availability: check that the Blood Oxygen app has not been deleted or restricted.
• Expectation: look in Health → Search → Respiratory → Blood Oxygen rather than expecting the result on the watch screen.

Apple’s support documentation says Blood Oxygen readings are intended for general fitness and wellness. They are not intended for medical use, diagnosis, self-diagnosis, or consultation with a doctor. Anyone with symptoms or a health concern should use appropriate medical equipment and seek professional medical advice.

What this means when buying an Apple Watch

If you specifically want the oxygen reading to appear on the watch itself, do not assume that a U.S. Series 9, Series 10, or Ultra 2 provides that experience. The redesigned U.S. workflow requires the paired iPhone for analysis and viewing, so it is less convenient when the iPhone is not nearby.

Before buying used or refurbished, verify:

• the exact model and region;
• the part number, including whether it ends in LW/A;
• the purchase date where relevant;
• the current watchOS and iOS versions;
• whether the Blood Oxygen app opens and produces a reading; and
• that the seller offers a return option if the feature state differs from the listing.

Apple-certified refurbished devices may reduce the risk of an inaccurately described listing, but buyers should still confirm the exact configuration. A standalone fingertip pulse oximeter may be a better fit for someone who wants a device dedicated to oxygen-saturation readings without an Apple Watch-to-iPhone workflow. It should not, however, be treated as a substitute for professional medical evaluation, and buyers should distinguish regulated or FDA-cleared products from general wellness gadgets.

Current status as of August 16, 2026

The consumer takeaway is straightforward: Apple’s original watch-processed feature and its later iPhone-calculated redesign must be treated as separate implementations. Apple lost the original patent dispute on appeal, but its redesigned U.S. feature remained usable after the ITC’s later enforcement ruling.

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