Check which Apple Watches support Blood Oxygen, how affected US models use iPhone for results, and why current availability is not a permanent guarantee.
Quick answer: On supported US Apple Watches purchased on or after January 18, 2024 with part numbers ending in LW/A, blood oxygen analysis happens on the paired iPhone and results appear in Health. Other purchase histories and regions can have different behavior. Check the exact model and Apple’s current regional support.
Updated September 5, 2026: removed guarantees of permanent availability and clarified ongoing litigation. Device behavior follows Apple’s Blood Oxygen documentation; legal statements below link to the relevant dated records.
What Actually Happened
Masimo brought a case at the US International Trade Commission over two pulse-oximetry patents. In October 2023 the ITC found a violation and issued a limited exclusion order. Apple pre-emptively pulled Series 9 and Ultra 2 from US sale that December, and after a brief stay the ban took effect in January 2024.
Apple resumed US sales on 18 January 2024 with the blood oxygen feature disabled in software. That is the state most people remember: you could buy the watch, the sensor was physically present, and the feature simply did not work.
Apple’s August 2025 announcement introduced redesigned Blood Oxygen support for affected Series 9, Series 10 and Ultra 2 watches with iOS 18.6.1 and watchOS 11.6.1.
How the Workaround Works
Apple's own description is that sensor data from the Blood Oxygen app is measured and calculated on the paired iPhone, with results viewable in the Respiratory section of the Health app.
In practice that means the hardware on your wrist still does the sensing. What moved is the computation and the display. You will not see a number appear on the watch face the way non-US users do — you take the measurement, then read the result on your phone.
The ITC’s ruling about a redesign is a legal determination about the accused products. Moving a calculation to another device should not be treated as a general explanation of patent scope or a guarantee about future proceedings.
For affected models, view results in the paired iPhone’s Health app. Follow Apple’s current instructions rather than assuming a result will always appear immediately on the watch.
Which Models Have Blood Oxygen in 2026
Two separate questions decide this, and conflating them is where most confusion comes from. First, does the watch have the sensor at all? Second, where and when did you buy it?
- Apple Watch Series 11 — has the sensor. US units use the iPhone-calculated form from launch.
- Apple Watch Ultra 3 — has the sensor. Same iPhone-calculated behaviour in the US.
- Apple Watch SE 3 — has no blood oxygen sensor at all. This is not a legal restriction; the hardware simply is not there. It also has no electrical heart sensor. See Apple’s SE 3 specifications for its sensor list.
- Series 9, Series 10, Ultra 2 — have the sensor. Affected US units regained the feature in iPhone-calculated form with the August 2025 update. Series 10 itself launched later in 2024; this does not mean it was sold in January.
If you are shopping and blood oxygen matters to you, the single most important thing to know is that SE 3 does not have it in any form, anywhere in the world. That is a hardware decision unrelated to the litigation, and no software update will change it.
How to Tell Which Version You Have
Apple draws the line by part number. US models purchased on or after 18 January 2024 have part numbers ending in LW/A, and those are the ones that route the calculation to the iPhone.
You can find the part number in Settings on the watch under General, then About. If yours does not end in LW/A, check the model, purchase history and regional documentation before assuming how the feature works.
Apple has been explicit that there is no impact on units purchased before the change, nor on any unit purchased outside the United States. Nothing was removed retroactively from a watch anyone already owned.
The dispute includes separate proceedings
The Federal Circuit’s March 2026 opinion affirmed the earlier ITC determination. Separately, Danaher’s quarterly filing reports an April 17 ITC determination that the redesigned watch did not violate the exclusion order, followed by Masimo’s notice of appeal in June. The filing describes the original orders as still in effect. That does not support saying the entire dispute has ended.
A separate damages case
The same Danaher filing describes a $634 million jury verdict in the California district-court patent litigation and distinguishes that case from the ITC matter. A damages figure is not an instruction about which Blood Oxygen app version your watch uses.
What This Means If You Are Buying
If you are in the US and want blood oxygen, buy Series 11 or Ultra 3 and accept that readings appear on your iPhone. Check current software and regional support; ongoing litigation means permanent future availability cannot be promised.
If you are buying an SE 3 for someone specifically because they want oxygen readings, buy something else — the sensor does not exist in that model.
Apple’s August 2025 announcement says that redesign did not affect previously purchased watches with the original feature or devices bought outside the US. Check current documentation for your own model before assuming which implementation it uses.
Apple describes Blood Oxygen as a general fitness and wellness feature, not for medical use. For the evidence and its limits, see our review of Apple Watch SpO2 accuracy against clinical data — availability and accuracy are separate questions, and the second one matters more.
Availability and limitations
Blood oxygen works on current US Apple Watches, just not the way it works elsewhere: the watch measures, the iPhone calculates, the Health app displays. The original order and the determination about redesigned products are separate, and the latter has also been appealed. Apple Watch SE models do not support Blood Oxygen, and that is a hardware choice rather than a legal one.
More from iPhoneExtra: Apple Watch SpO2 Research | Apple Watch Series 11 Health Features | Apple Watch ECG Accuracy.
