Samsung Galaxy Watch Ultra Review: Sleep Apnea, ECG, and the Ultra2

Samsung’s Galaxy Watch Ultra (2024) carries the first FDA authorized sleep apnea feature on a smartwatch plus passive AFib alerts; now that the Galaxy Watch Ultra2 has replaced it, the question is how much a watch can really tell you about the breathing you never hear.

At Stanford, 152 adults signed up to spend two nights apiece in a sleep laboratory, wired for a full overnight sleep study, the kind that tracks brain waves, breathing effort, airflow, and blood oxygen. On one wrist, each also wore a Samsung Galaxy Watch. Across 1,850 hours of recorded sleep, researchers asked a simple question: could the watch, reading only what passes through the skin of the wrist, flag the people whose airways were collapsing 15 or more times an hour? It could. Using Samsung’s default setting, the watch caught 94.1 percent of people with moderate to severe obstructive sleep apnea.

That number is the strongest argument for the Samsung Galaxy Watch Ultra, Samsung’s rugged smartwatch, launched in July 2024 at $649.99 alongside the Galaxy Watch7. That generation launched with Samsung’s sleep apnea feature, which the company announced as the first of its kind to be authorized by the FDA (Samsung also brought it to some older watches), and the Ultra also supports Samsung’s FDA cleared irregular heart rhythm notification and an ECG app.

As of October 2026, the Ultra has a successor, the Galaxy Watch Ultra2, announced at Samsung’s Galaxy Unpacked event in July 2026. The science behind the original is still the heart of the story.

What Is the Samsung Galaxy Watch Ultra, and Has It Been Replaced?

The Samsung Galaxy Watch Ultra is a rugged smartwatch made by Samsung that runs Wear OS and pairs with Android phones. It launched in July 2024 at $649.99 with Samsung’s FDA authorized sleep apnea feature and FDA cleared irregular rhythm alerts. Samsung announced its successor, the Galaxy Watch Ultra2, at Galaxy Unpacked in July 2026.

The Ultra was Samsung’s answer to the outdoor smartwatch: a tougher, adventure-focused design and a battery Samsung rated at up to 100 hours. In 2025 Samsung quietly refreshed it with a new color and double the storage, and retailers cut its price deeply during sales; TechRadar reported a 45 percent discount on the previous model in the run-up to the Ultra2 launch.

The Galaxy Watch Ultra2 arrived in July 2026 at $699.99, with launch coverage highlighting a bigger battery and a brighter screen in a design that keeps the original’s look. The health features that made the first Ultra notable run largely through Samsung’s software, but we could not confirm feature-by-feature availability on the Ultra2 from the sources we reviewed, so check Samsung’s listing before you buy either watch for a specific health feature.

Those health features live in the Samsung Health Monitor app. Samsung’s FDA authorized sleep apnea feature, its FDA cleared Irregular Heart Rhythm Notification, and its ECG app all run there, and the app requires an Android phone running Android 12 or newer. That one fact decides the purchase for many readers: this is not a watch for iPhone owners.

This review focuses on what makes the Ultra clinically interesting: the sleep apnea feature and Samsung’s AFib detection. For Samsung’s mainstream watch from the same generation, see our Galaxy Watch 7 review.

How Does the Galaxy Watch Ultra Detect Sleep Apnea and AFib?

The Ultra’s optical sensor shines light into the wrist and measures what bounces back. During sleep, dips in blood oxygen let Samsung’s software estimate how often breathing is disrupted, the basis of its sleep apnea feature. The same optical pulse signal powers its passive AFib alerts, and its ECG app records the heart’s electrical activity on demand.

The collapsing airway. When you fall asleep, the muscles that hold your throat open relax. In obstructive sleep apnea, the soft tissue at the back of the throat sags far enough to narrow or close the airway. Airflow drops (a hypopnea) or stops entirely (an apnea), the chest keeps heaving against a closed door, and blood oxygen begins to fall. Eventually the brain registers the emergency and jolts you toward wakefulness, usually without you noticing. The airway snaps open, you gasp, oxygen recovers, and the cycle starts again. Sleep doctors count these events per hour as the apnea-hypopnea index, or AHI. Fifteen or more events an hour marks moderate to severe disease; in the Stanford study, Samsung’s default setting flagged an estimated AHI of 15 or more.

Each event is a small physiological assault. Oxygen falls, the nervous system floods the body with stress signals, blood pressure spikes, and the heart is forced to work against the changing pressure in the chest. Repeated dozens or even hundreds of times a night for years, that pattern is linked to high blood pressure, atrial fibrillation, and cardiovascular events. In an observational study that followed men in Spain for a mean of about 10 years, untreated severe sleep apnea was associated with roughly three times the odds of fatal and of non-fatal cardiovascular events compared with healthy men (Lancet, 2005). Event rates in men treated with CPAP were far lower, close to those of healthy men. That study was observational, so it cannot prove CPAP caused the difference, but it shows why finding the disease matters.

Reading oxygen through the wrist. Oxygen-rich and oxygen-poor blood absorb red and infrared light differently. By comparing how much of each wavelength comes back, a sensor can estimate blood oxygen saturation, the same principle a fingertip pulse oximeter uses. At the wrist, the light reflects back rather than passing through a finger, which makes the signal weaker and more vulnerable to movement. During an apnea, the signature is distinctive: oxygen sagging, then rebounding as breathing resumes. Samsung’s software turns those patterns into an estimated AHI. The company has not published the full algorithm, which is why independent testing against laboratory sleep studies matters so much.

Listening for the irregular beat. The Ultra’s passive AFib alert relies on the same optical sensor tracking pulse timing. In atrial fibrillation, the upper chambers quiver instead of contracting, and impulses reach the ventricles at random, so the gaps between beats turn erratic. When the watch’s algorithm sees that pattern, Samsung’s Irregular Heart Rhythm Notification alerts you. The ECG app adds an electrical picture on demand: touch the watch with a finger of your other hand, and it records a single-lead tracing, the arm-to-arm view cardiologists call lead I, that software classifies for signs of AFib.

Together, the two systems work like a smoke detector and a camera. The passive alert listens all night without being asked; the ECG captures a precise picture when you choose to look. Few watches pair both with a sleep apnea screen, which is what made the Ultra unusual.

How Accurate Is the Galaxy Watch Ultra? What the Research Shows

Independent studies of Samsung watches are encouraging. In a 2026 Stanford study of 152 adults, a Galaxy Watch caught 94.1 percent of moderate to severe sleep apnea at Samsung’s default setting, with 66.7 percent specificity. For AFib, a 2025 meta-analysis pooled Samsung watches at 97 percent sensitivity and 96 percent specificity, though individual studies range lower.

Sleep apnea: strong in a high-risk group. The Stanford study, published in 2026 in the Journal of Clinical Sleep Medicine, enrolled 152 adults aged 22 or older who either had a prior diagnosis of moderate to severe sleep apnea or a high pretest likelihood of it, and 147 completed two in-lab sleep studies with the watch on, plus at least three watch-only nights at home. Against polysomnography, the Galaxy Watch reached an area under the curve of 0.94 for moderate to severe sleep apnea. At Samsung’s default threshold, an estimated AHI of 15, it caught 94.1 percent of true cases but correctly cleared only 66.7 percent of people without moderate to severe disease, meaning a meaningful share of positive flags were false alarms. When the researchers raised the threshold to an estimated AHI of about 26, sensitivity fell to 82.4 percent and specificity rose to 94.9 percent. Among people with a high hypoxic burden, a measure of how deep, long, and frequent the oxygen drops are, the watch separated high-risk from low-risk patients perfectly.

Two cautions keep those numbers honest. First, the study population was enriched with people likely to have sleep apnea. Screening tools usually look better in high-risk groups than in the general public, so the false-alarm rate could be different for a healthy 35-year-old who snores occasionally. Second, the abstract does not state who funded the work, so we cannot assess sponsor influence. The study was prospective, used repeated laboratory testing, and was registered in advance (ClinicalTrials.gov NCT06603441), all signs of careful design.

An earlier University of California, San Diego study tested an older model, the Galaxy Watch 4, against in-lab polysomnography in 51 adults (Journal of Clinical Sleep Medicine, 2024). Its overnight blood oxygen readings tracked the laboratory oximeter with a root-mean-square error of 2.54 percentage points, and a model based on the watch’s oxygen data predicted moderate to severe sleep apnea (AHI above 15) with an area under the curve of 0.80, and severe disease (AHI above 30) with 0.89. In a Czech laboratory test of 18 healthy volunteers breathing low-oxygen gas mixtures, a Galaxy Watch 5 met the accuracy threshold of the international pulse oximeter standard, both at normal oxygen levels and during induced desaturation below 90 percent, though an Apple Watch 8 performed best of the three watches tested (Sensors, 2023).

The pattern across the three studies is consistent: Samsung’s wrist oximetry is good enough to be useful for screening, best at catching severe disease, and least reliable at telling mild disease from none. That is exactly the profile you want in a tool meant to send people for a proper sleep test, and exactly the profile you do not want if you treat a quiet watch as proof you are fine.

AFib: among the better-tested watches. Samsung watches have been studied more often than most. In the BASEL Wearable Study at University Hospital Basel, 201 cardiology patients recorded ECGs on five consumer devices (JACC: Clinical Electrophysiology, 2023). The Samsung Galaxy Watch 3 detected AFib with 85 percent sensitivity and 75 percent specificity, tied with the Apple Watch 6, ahead of the Fitbit Sense (66 percent) and Withings ScanWatch (58 percent), with 17 percent of Samsung tracings labeled inconclusive. A French study of 200 patients, half in AFib, found the Samsung Galaxy Watch Active 3’s automated reading reached 88 percent sensitivity and 81 percent specificity, comparable to an Apple Watch 5, but 15 percent of its tracings were uninterpretable by experts, far more than the 2 to 4 percent for Apple and Withings (Frontiers in Cardiovascular Medicine, 2022).

Pooled data look better than any single study. A 2025 diagnostic meta-analysis in JACC: Advances, covering 26 studies and 17,349 patients, put Samsung devices at 97 percent sensitivity and 96 percent specificity, against 94 and 97 percent for Apple and 89 and 95 percent for Withings. Meta-analyses mix study designs and populations, and its authors reported high heterogeneity, so read those figures as a ceiling rather than a promise. The single-hospital studies, in which inconclusive tracings counted against the device, are a better guide to what a real user will experience.

One more caveat applies to every wrist ECG. A 2025 Basel study of 256 patients found that baseline ECG quirks sharply raise the odds of an inconclusive result: ventricular pacing more than sixfold, conduction delays and extra beats about twofold (JACC: Clinical Electrophysiology, 2025). If you have a pacemaker or known conduction disease, expect more shrugs from any smartwatch, Samsung’s included.

What the Galaxy Watch Ultra Gets Right

The Ultra gets the hardest thing right: it pairs an FDA authorized sleep apnea screen with FDA cleared passive AFib alerts, both backed by independent studies of Samsung watches, on a watch durable enough for outdoor use and with enough battery to stay on overnight.

A screen for a disease most people do not know they have. A 2019 analysis in The Lancet Respiratory Medicine estimated that 936 million adults aged 30 to 69 worldwide have obstructive sleep apnea, 425 million of them with moderate to severe disease. That analysis was funded by ResMed, a maker of sleep apnea treatment devices, but its point stands: the disease is common and widely undiagnosed. A watch that flags likely cases during ordinary sleep lowers the barrier to the first step, which is a conversation with a clinician.

Sensitivity where it counts. Catching 94.1 percent of moderate to severe sleep apnea at the default setting means few serious cases slip past. The cost is false alarms, but for a screening tool that leads to a confirmatory test, that is usually the right trade.

Two layers of heart rhythm protection. The passive Irregular Heart Rhythm Notification watches without being asked, and the ECG app lets you capture a tracing when you feel a flutter. Samsung’s AFib detection holds up well in head-to-head studies.

Battery for overnight data. Samsung rated the Ultra at up to 100 hours. Overnight features only work on nights the watch is worn, and a watch that does not need charging every night protects that record.

Built for the outdoors. The rugged design suits hikers, swimmers, and endurance athletes who would rather not baby a smartwatch.

Where the Galaxy Watch Ultra Falls Short

The Ultra’s clinical features work only with Android phones, its sleep apnea screen produces many false alarms at the default setting and was validated mainly in high-risk adults, and its AFib ECG returns uninterpretable tracings more often than some rivals in one study. It is also now a previous-generation watch.

No iPhone, and check your Android. The sleep apnea, irregular rhythm, and ECG features run through Samsung Health Monitor, which requires Android 12 or newer. iPhone owners cannot use them. If you have a non-Samsung Android phone, confirm compatibility with Samsung before buying.

False alarms are built in. At the default threshold in the Stanford study, specificity was 66.7 percent: roughly one in three people without moderate to severe sleep apnea were flagged anyway. A positive result is a reason to see a clinician, not a diagnosis.

Mild disease is out of scope. The default threshold sits at moderate disease, an estimated AHI of 15. Mild sleep apnea, which can still cause symptoms, is not what it is designed to catch, so a negative result does not mean your sleep is healthy.

Screening for AFib in people who feel fine is unproven. In 2022 the US Preventive Services Task Force concluded that the evidence was insufficient to weigh the benefits and harms of screening adults 50 and older without symptoms (JAMA, 2022). An alert is worth acting on; constant monitoring is not proven to prevent strokes.

One lead, one rhythm question. A single-lead ECG cannot detect a heart attack or replace a 12-lead ECG. Chest pain, pressure, or shortness of breath is an emergency: call 911.

A watch at the end of its line. The Ultra2 has replaced it, and new features tend to arrive first on new models. If you are paying anywhere near the original $649.99, the newer watch is the better buy.

Galaxy Watch Ultra vs Galaxy Watch Ultra2 vs Garmin Venu 3 vs Fitbit Charge 6

The Ultra2 is the direct successor, with a bigger battery and brighter screen at $699.99. A Garmin Venu 3 offers longer battery and an ECG but no FDA cleared passive AFib alerts or sleep apnea feature. A Fitbit Charge 6 adds passive AFib alerts and an ECG for far less, without a sleep apnea screen.

Feature	Galaxy Watch Ultra	Galaxy Watch Ultra2	Garmin Venu 3	Fitbit Charge 6
FDA authorized sleep apnea feature	Yes (De Novo)	Not confirmed in our sources	None found	None found
FDA cleared passive AFib alerts	Yes (Irregular Heart Rhythm Notification)	Not confirmed in our sources	None found	Yes (Irregular Rhythm Notifications)
ECG app	Yes, via Samsung Health Monitor	Not confirmed in our sources	Yes, FDA cleared Garmin ECG App	Yes, FDA cleared Fitbit ECG App
Independent AFib ECG data	Galaxy Watch 3: 85% sensitivity (BASEL)	Not separately tested	None published that we found	Fitbit’s app on the Sense: 66% sensitivity (BASEL)
Rated battery	Up to 100 hours	Bigger than the Ultra, per launch coverage	Up to 14 days	Up to 7 days
Launch price and status (October 2026)	$649.99 (2024); superseded	$699.99 (July 2026); current	$449.99 (2023); superseded by Venu 4	$160 (2023); replaced by Fitbit Edge

If you want Samsung’s newest rugged watch, the Ultra2 is the obvious choice. If you want a long-lasting smartwatch with an on-demand ECG and no subscription, see our Garmin Venu 3 review; if you want passive AFib alerts in an inexpensive band, see our Fitbit Charge 6 review. Apple’s rugged rival is covered in our Apple Watch Ultra 2 review. If sleep apnea is your main concern and you prefer a ring, our RingConn Gen 2 review covers a ring built around it, and if you want an actual diagnostic test, a clinician can order a home sleep test such as WatchPAT One. Browse all our cardiology device reviews.

How Much Does the Galaxy Watch Ultra Cost, and Is It Covered or HSA/FSA Eligible?

The Galaxy Watch Ultra launched at $649.99 in July 2024 and has been deeply discounted since, with TechRadar and Neowin reporting 45 percent off during sales. As of October 2026, its successor, the Galaxy Watch Ultra2, lists at $699.99. Samsung’s health features need no subscription. We found no evidence that insurers cover it.

Practically, as of October 2026, the original Ultra is a discount purchase. At a deep discount, it offers the headline health features that made it notable: an FDA authorized sleep apnea screen, FDA cleared passive AFib alerts, and an ECG app, in a rugged watch. Near its original price, the Ultra2 is the better buy, with a bigger battery and a longer runway of software support. Launch promotions have also cut the Ultra2’s effective price, so compare before you choose.

We could not verify that the Galaxy Watch Ultra qualifies for HSA or FSA funds; ask your plan administrator before counting on it. If the watch flags possible sleep apnea, the follow-up home sleep test or laboratory study is a medical expense that insurance often covers when a clinician orders it; check your plan.

Who Should Buy the Galaxy Watch Ultra, and Who Should Skip It?

The Ultra suits Android users, especially those who snore or wake unrefreshed, who want an FDA authorized sleep apnea screen and passive AFib alerts in a durable outdoor watch, bought at a discount. It is the wrong choice for iPhone users, anyone who needs a diagnosis, and buyers who can only find it near full price.

Good candidates:

• Android users with loud snoring, witnessed pauses in breathing, or daytime sleepiness who want a low-friction first screen before talking to a clinician.
• Adults who want passive AFib alerts and an on-demand ECG in one watch.
• Hikers, swimmers, and endurance athletes who need a rugged smartwatch with multi-day battery.
• Buyers who find the original Ultra at a deep discount.

Better served by something else:

• Anyone with chest pain, fainting, or a racing heart with shortness of breath: that is an emergency. Call 911.
• iPhone users, who cannot use the Samsung Health Monitor features.
• People who already suspect sleep apnea strongly: skip the screen and ask a clinician for a home sleep test or laboratory study.
• People already treated with CPAP: your therapy data and your sleep clinician are the right guide, not a screening watch; see our ResMed AirSense 11 review.
• Buyers who can only find it near full price: the Ultra2 is the better buy.

If the watch flags sleep apnea or an irregular rhythm, the Healthcare Discovery doctor directory lists sleep medicine specialists, cardiologists, and electrophysiologists by state.

What This Means for You

Sleep apnea is one of the quiet accomplices of the Silent Assassin, cardiovascular disease. Every collapse of the airway drops oxygen and spikes blood pressure, and over years that pattern is linked to hypertension, atrial fibrillation, and heart attacks and strokes. Atrial fibrillation, in turn, carried a near fivefold excess risk of stroke in the Framingham Study’s 34-year follow-up of 5,070 people (Stroke, 1991). A watch that screens for both is aiming at two of the Silent Assassin’s favorite tools, which is why it belongs in the larger story we tell in the Four Villains of Health and Longevity.

The pillar at stake is Sleep, but not in the way most sleep trackers frame it. A sleep score tells you how you slept. A sleep apnea screen asks whether something is actively harming you while you sleep, and the answer can change your life: sleep apnea is treatable, and in the Spanish cohort, men whose severe disease was treated with CPAP had cardiovascular event rates close to those of healthy men. Breath is the other pillar here, quite literally; the watch is listening, in effect, for the breaths you miss.

And Mindset matters. A flag from your wrist is not a diagnosis, and a quiet watch is not a clean bill of health. Treat the Ultra as a smart first question: a reason to book the sleep study you have been putting off, or to show a clinician the ECG you captured during a flutter. The 152 adults who slept wired up at Stanford showed that a watch can hear a struggling airway surprisingly well. What happens after it does is still up to you and your doctor.

Frequently Asked Questions

Sources

1. Alavi A, et al. Smartwatch-based detection of moderate-to-severe and high-risk obstructive sleep apnea. Journal of Clinical Sleep Medicine, 2026. DOI
2. Browne SH, et al. Performance of a commercial smart watch compared to polysomnography reference for overnight continuous oximetry measurement and sleep apnea evaluation. Journal of Clinical Sleep Medicine, 2024. DOI
3. Walzel S, et al. Evaluation of leading smartwatches for the detection of hypoxemia: comparison to reference oximeter. Sensors, 2023. DOI
4. Mannhart D, et al. Clinical validation of 5 direct-to-consumer wearable smart devices to detect atrial fibrillation: BASEL Wearable Study. JACC: Clinical Electrophysiology, 2023. DOI
5. Abu-Alrub S, et al. Smartwatch electrocardiograms for automated and manual diagnosis of atrial fibrillation: a comparative analysis of three models. Frontiers in Cardiovascular Medicine, 2022. DOI
6. Barrera N, et al. Accuracy of smartwatches in the detection of atrial fibrillation: a systematic review and diagnostic meta-analysis. JACC: Advances, 2025. DOI
7. Isenegger C, et al. Inconclusive single-lead ECGs from smart devices: impact of baseline ECG anomalies. JACC: Clinical Electrophysiology, 2025. DOI
8. Benjafield AV, et al. Estimation of the global prevalence and burden of obstructive sleep apnoea: a literature-based analysis. Lancet Respiratory Medicine, 2019. DOI
9. Marin JM, et al. Long-term cardiovascular outcomes in men with obstructive sleep apnoea-hypopnoea with or without treatment with continuous positive airway pressure: an observational study. Lancet, 2005. DOI
10. US Preventive Services Task Force. Screening for atrial fibrillation: recommendation statement. JAMA, 2022. DOI
11. Wolf PA, Abbott RD, Kannel WB. Atrial fibrillation as an independent risk factor for stroke: the Framingham Study. Stroke, 1991. DOI
12. Samsung. Samsung’s sleep apnea feature on Galaxy Watch first of its kind authorized by US FDA (press release). Samsung Newsroom
13. Samsung. Samsung announces FDA-cleared Irregular Heart Rhythm Notification for Galaxy Watch (press release). Samsung Newsroom
14. Samsung. Galaxy Unpacked July 2026: a first look at Galaxy Watch Ultra2 and Galaxy Watch9 (press release). Samsung Newsroom