Short answer
Galaxy Watch 8 tracks heart rate, sleep, stress, blood oxygen and skin temperature, and adds four newer features: Bedtime Guidance, Vascular Load, Antioxidant Index and Running Coach (1, 2). On top of those wellness scores sit a few regulated tools in the US: an ECG app, irregular heart rhythm notifications, an FDA-authorized sleep apnea feature and cuff-calibrated blood pressure (3, 4, 5).
The most useful numbers are the boring ones. Resting heart rate, sleep timing and how your stress readings move across a week tell you more than any single daily score. The newer scores are best read as trends over two to four weeks, not as verdicts on one morning.
If the Samsung Health dashboard feels like too many numbers and you've started to distrust all of them, that's not your fault. The watch shows everything it can measure; deciding what matters is a separate job, and this guide does that part.
Note: this article is for general education and is not medical advice. The watch's wellness features are not designed to diagnose or treat any condition. Chest pain, fainting, severe shortness of breath, or a fast or irregular heartbeat with lightheadedness are emergencies: call 911 or your local emergency number. Device features were checked on Samsung's official pages on November 6, 2026, and can change with software updates and by country. This guide is published by Welltory, which makes one of the apps mentioned. Samsung and Galaxy are trademarks of Samsung Electronics; Welltory is not affiliated with Samsung.
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What Galaxy Watch 8 measures: the full list in one table
Samsung announced Galaxy Watch 8 and Watch 8 Classic in July 2025 with One UI 8 Watch (1). Galaxy Watch 9 followed in August 2026 (6), so Watch 8 is now the previous generation, often sold at a lower price. Its health features fall into three groups.
| Feature | What it measures | Type | Needs a Samsung phone? |
|---|---|---|---|
| Heart rate, stress, sleep stages | Pulse from the optical sensor; stress from heart signals; sleep from movement and heart rate | Wellness | No |
| Blood oxygen during sleep, skin temperature | Overnight oxygen dips; overnight temperature for cycle tracking | Wellness | No |
| Energy Score | Daily score built from your sleep, activity and heart data | Wellness | Insights need one |
| Bedtime Guidance | Suggested bedtime from three days of sleep | Wellness | Bedtime Sync needs one |
| Vascular Load | Load on blood vessels during sleep | Wellness (launched as a Labs feature) | No (Android 10+) |
| Antioxidant Index | Carotenoids in the skin of your thumb | Wellness (launched as a Labs feature) | No (Android 10+) |
| Running Coach | 12-minute test run, then a training plan | Fitness | No |
| Body composition | Body fat, muscle and water through BIA electrodes | Wellness | No |
| ECG app and irregular rhythm notifications | Heart rhythm, signs of atrial fibrillation | Regulated (US) | Yes |
| Sleep apnea feature | Signs of moderate to severe obstructive sleep apnea | FDA De Novo authorized | Yes |
| Blood pressure | Systolic and diastolic, after cuff calibration | Not for diagnosis | Yes (Android 12+) |
Samsung's own footnote sets the frame for everything in the "wellness" rows: these features "are intended for general wellness and fitness purposes only," and the measurements "are for personal reference only" (2).
The everyday numbers: heart rate, sleep, stress and Energy Score
Heart rate and resting heart rate
The optical sensor on the back shines light into your wrist and reads the pulse wave in your blood vessels. This is the same principle, photoplethysmography, used by almost every smartwatch and ring. It works best when you're still and the watch sits snugly a finger's width above the wrist bone. During hard intervals or weightlifting, wrist readings lag and drift more than a chest strap.
What to read: your resting heart rate trend, not single readings. A resting rate that runs several beats above your usual level for a few days in a row often reflects poor sleep, alcohol, a late meal, stress, heavy training or an infection starting. For what's normal, see our guide to how to check your pulse.
Sleep stages and sleep score
Galaxy Watch 8 records light, deep and REM sleep, along with blood oxygen during sleep (3). Consumer trackers are good at telling sleep from wake and weaker at stages. In a lab study of 34 young adults, most consumer sleep trackers matched or beat research actigraphy at detecting sleep versus wake, but their sleep-stage results were inconsistent, and accuracy dropped on nights of disrupted sleep (7).
What to read: total sleep time and how regular your bedtime and wake time are. Treat the deep and REM split as a rough estimate. Our guide to what a good sleep score is explains how sleep scores are built and why two apps can disagree.
Stress
The watch tracks stress automatically through the day and can send a High Stress Alert (3). Wrist stress scores are built from heart signals, which also rise with caffeine, heat, standing up, digestion and climbing stairs. A "high stress" reading while you walk up to the office isn't a mood report.
What to read: stress readings taken while you sit still, and how often you see high readings across a week. One spike means little; a week of high resting readings is worth noticing.
Energy Score
Energy Score is a daily number meant to summarize how ready you are for the day. Samsung builds it from your sleep, activity and heart data; the US page describes it as a score from yesterday's sleep and heart rate, and the UK support page lists sleep quality, stress and activity history (3, 8). Energy Score insights are not available with non-Samsung Android phones (3).
What to read: the direction over a week, and whether a low score matches how you feel. When the score and your body disagree, read our piece on why your wearable and your feelings disagree.
Bedtime Guidance: a bedtime from three nights of data
Bedtime Guidance looks at your last three days of sleep to estimate sleep pressure and your circadian rhythm, then suggests a time to wind down and reminds you to stay consistent (2). It's aimed at people whose schedules got knocked off course, for example by late weekend nights. Samsung states that it is "not intended for use in the detection, diagnosis or treatment of any medical condition or sleep disorder" (2).
How to use it well:
Wear the watch every night for at least three nights before you trust the suggestion.
Pick one suggested window and keep it for a week, weekends included.
Move toward the suggested window gradually rather than in one jump, as Samsung's own tip advises (8); 15 to 30 minutes every few days is a gentle pace.
Check your sleep regularity and morning resting heart rate after the week. If both improve, keep the new time.
Vascular Load: what the sleep-time number means
Vascular Load estimates the load on your blood vessels while you sleep (1). Samsung's UK support page says it uses pulse-wave analysis from the optical sensor and that higher values may relate to arterial stiffness, which is influenced by salt intake, stress and inactivity (8).
Practical points from Samsung's own notes:
It needs the watch worn during sleep on at least three of the most recent 14 nights (2).
It launched as a Labs (experimental) feature on Galaxy Watch Ultra and later watches (2).
It's a wellness estimate, not a blood pressure reading and not a test for heart disease.
What to read: whether your value is stable over weeks and whether it moves with obvious causes, such as a run of late salty dinners, poor sleep or a stressful stretch. Don't change medication or diet drastically because of one reading. If you have high blood pressure or heart disease, a cuff reading and your doctor's plan come first.
Antioxidant Index: a five-second thumb test
Antioxidant Index measures carotenoids, the pigments in orange and green fruit and vegetables that build up in skin. You place your thumb on the sensor on the back of the watch for about five seconds and get a score with a color band (1, 2).
The idea comes from research devices. Skin carotenoid scores from a dedicated reflection-spectroscopy device, the Veggie Meter, correlate with carotenoids in blood (r = 0.81 with serum, r = 0.71 with plasma in studies the authors cite), and they respond to a change in diet within weeks (9). The same study also found that two devices measuring the same person differed by about 14% on average (9). These results come from a lab device, not from Samsung's watch, so they show what the method can do, not how accurate this watch is.
Samsung notes that "repeated measurements due to uneven skin texture may lead to inaccurate results" (2). To get readings you can compare:
Wash and dry your hands, and skip lotion beforehand.
Use the same thumb, at the same time of day.
Press with the same light pressure and keep still for the full reading.
Compare monthly averages, not one test against another.
What to read: a slow upward drift after you add more vegetables is a nice confirmation. A single low reading isn't a deficiency diagnosis.
Running Coach: a fitness number you control
Running Coach starts with a 12-minute run, rates your running level from 1 to 10, then builds a three- to five-week plan toward goals such as a 5K, 10K, half marathon or marathon, with real-time pace and heart rate zone guidance (1, 8).
What to read: your level after each block of training. It's one of the few numbers on the watch that you change directly through effort. If you're returning after illness or long inactivity, start easier than the plan suggests and check with your doctor first if you have a heart condition.
The regulated features: ECG, irregular rhythm, sleep apnea and blood pressure
These four are different from the scores above. They have clear rules about who should use them and what a result means.
ECG app. You hold a finger on the button and the watch records a single-lead ECG to look for signs of atrial fibrillation. Samsung's US page says the ECG app is for adults 22 and older and is not a replacement for traditional diagnosis (3).
Irregular heart rhythm notifications. In the background, the watch looks for pulse patterns suggestive of atrial fibrillation and prompts you to take an ECG. Samsung notes that the watch won't notify you of every episode, and no notification doesn't mean no disease (3).
Sleep apnea feature. It received De Novo authorization from the US FDA in February 2024. It's for adults 22 and older who have not been diagnosed with sleep apnea, and it needs two nights of more than four hours of sleep tracking within a ten-day window (4). It looks at overnight oxygen dips and is "not intended to provide a stand-alone diagnosis" (3).
Blood pressure. Samsung began a phased US rollout on March 31, 2026, for Galaxy Watch4 and later with Wear OS 4 or higher, paired with a Samsung Galaxy phone on Android 12 or higher. You calibrate with a separate upper-arm cuff, and recalibrate every 28 days (5). Samsung states that the feature "is not intended to prevent or diagnose high blood pressure," and its announcement doesn't describe the blood pressure feature itself as FDA-cleared (5). We explain the details in Galaxy Watch blood pressure: how it works and how accurate it is and in can a smartwatch measure blood pressure?.
What to read: any irregular rhythm notification or apnea result is a reason to talk to a doctor, not to self-diagnose. Blood pressure from the watch is a trend line between cuff readings, not a replacement for the cuff.
Body composition: when the number is worth checking
Galaxy Watch 8 uses bioelectrical impedance analysis (BIA): you touch two fingers to the buttons and a tiny current estimates body fat, skeletal muscle and body water (3). BIA estimates swing with hydration, a recent meal, exercise and even the time of day.
What to read: one reading a week, taken the same way — morning, after the bathroom, before food and exercise. Compare monthly averages. If the number disagrees with how your clothes fit, trust the clothes.
What works if you don't have a Samsung phone
Galaxy Watch 8 pairs with Android phones, but several features need a Samsung Galaxy phone. Samsung's US page lists the ECG app, the Sleep Apnea feature, Energy Score insights and Bedtime Sync among features "not available with non-Samsung Android mobile devices" (3). Blood pressure also needs a Galaxy phone on Android 12 or later (5). Vascular Load and Antioxidant Index were announced for Android phones running Android 10 or above with an up-to-date Samsung Health app (2). Apple's iPhone isn't supported.
If you use a Pixel or another Android phone, the core tracking still works: heart rate, sleep, stress, workouts. Other apps, Welltory included, can read Samsung Health data, so you're not locked into one dashboard (10). Our guides to the Health Connect app and Google Fit vs Samsung Health explain how the data moves between apps.
Which numbers to read daily, weekly and rarely
This is the part most reviews skip. A watch that measures a dozen things invites you to check a dozen things, and that's how people end up anxious about scores that were never meant to be read daily.
| How often | Numbers | Why |
|---|---|---|
| Glance daily | Sleep time, morning resting heart rate | Fast, reliable signals of a rough night or an oncoming cold |
| Review weekly | Stress pattern, Energy Score trend, bedtime regularity | Patterns need several days to mean anything |
| Review monthly | Vascular Load, Antioxidant Index, body composition, running level | Slow-moving measures with noisy single readings |
| Only when prompted or advised | ECG, sleep apnea check, blood pressure | Tools with clear rules for use and a doctor at the other end |
The rule of thumb: the slower a body system changes, the less often you should look at its number.
How to set up Galaxy Watch 8 so the numbers mean something
Update everything first. Watch software, Samsung Health and Galaxy Wearable. Several features require a minimum Samsung Health version (2).
Enter your real age, height, weight and sex. Scores and calorie estimates depend on them.
Fit the watch correctly. Snug, one finger's width above the wrist bone; slightly tighter for workouts.
Wear it to bed. Bedtime Guidance needs three nights; Vascular Load needs at least three nights within two weeks (2).
Turn on continuous heart rate and stress tracking, and set the high stress alert only if alerts help rather than worry you.
Give it two weeks before judging. Your baseline forms from your own data.
Note the obvious causes. Late meals, alcohol, travel, illness and hard workouts explain most bad days.
Common mistakes with Galaxy Watch 8 health data
Reading stress during movement. Stairs and walking raise the same signals stress does.
Comparing your score with a friend's. Scores are built around your own baseline.
Chasing a perfect Energy Score. A low score after a hard training day is the watch working as intended.
Repeating the Antioxidant Index test until it looks better. Samsung warns that repeated measurements can be inaccurate (2).
Treating blood pressure readings as cuff-grade. Recalibrate every 28 days and confirm high readings with a cuff (5).
Ignoring a real symptom because the scores look fine. A watch can miss things. How you feel counts.
Galaxy Watch 8 or Galaxy Watch 9?
Galaxy Watch 9 went on sale in August 2026 with new features, including Vitals, which compares five overnight signals against your personal baseline, a Heart Health Score, a Fitness Index and a Daily Cardio Load (6). Samsung's announcement also says the 40 mm Watch 9 has a 20% larger battery than the comparable Watch 8 (6).
If those features matter to you, compare on Samsung's site on the day you buy, since some features reach older watches through updates and some don't. If you mainly want heart rate, sleep, stress, ECG and blood pressure, Watch 8 covers them. Samsung's US site listed Galaxy Watch 8 from $299.99 on November 6, 2026 (3); prices change often. Our broader best Android smartwatch for heart health guide compares Galaxy, Pixel and Garmin.
Living with a Galaxy Watch 8: the questions people ask next
Is the Galaxy Watch 8 waterproof?
It's water resistant, rated 5ATM and IP68, and meets MIL-STD-810H. Samsung's footnote describes the IP68 rating as water resistance in up to 5 feet of water for up to 30 minutes, and recommends rinsing and drying it after exposure (3). A 5ATM rating is generally meant for surface swimming, not high-speed water sports or diving; check Samsung's care guidance for your use.
Does Galaxy Watch 8 measure blood pressure?
Yes, in the US since a phased rollout that began March 31, 2026, with a Samsung Galaxy phone. You need to calibrate with an upper-arm cuff and repeat that every 28 days (5).
Does Galaxy Watch 8 have stress monitoring?
Yes. It tracks stress automatically through the day and can send high stress alerts (3). Readings are most meaningful when you're sitting still.
Can Galaxy Watch 8 measure blood oxygen?
Yes. It tracks blood oxygen during sleep, and the sleep apnea feature uses overnight oxygen dips (3).
How accurate is Galaxy Watch 8 heart rate?
At rest and during steady activity, optical wrist sensors generally track heart rate well. During sprints, weights and activities with lots of wrist movement, readings lag and drift. If precise workout heart rate matters, pair a chest strap.
Before you blame yourself
When a watch gives you a poor sleep score, a low Energy Score and a stress alert in the same morning, it's easy to feel you're doing something wrong. Before you blame yourself, look at your own data. Most bad scores have a visible cause: a late dinner, a drink, a hard workout, a short night or a cold starting.
Pick one feeling and match it to one cause you can see. "I feel wired at night" might line up with high evening stress readings. "I'm tired every afternoon" might line up with bedtimes that swing by two hours. Then choose one lever for one to two weeks: a fixed bedtime, no alcohol on weeknights, or dinner two hours earlier. Watch the trend, not the daily score.
When to see a doctor
See a doctor if:
You get an irregular heart rhythm notification or an ECG result showing signs of atrial fibrillation.
The sleep apnea feature flags signs of sleep apnea, or someone tells you that you snore loudly and stop breathing in your sleep.
Your blood pressure readings are repeatedly high, confirmed with a cuff.
Your resting heart rate stays well above your usual level for more than a week without an obvious reason.
You have palpitations, unexplained fatigue, or shortness of breath on exertion, whatever the watch says.
Call 911 or your local emergency number for chest pain or pressure, fainting, severe shortness of breath, or a fast or irregular heartbeat with lightheadedness. Don't wait for the watch to confirm it.
How to bring this up with your doctor
What to ask for, by name. If you got a rhythm alert: "Can we check this with a 12-lead ECG, and would a heart monitor I wear for a few days help?" If the apnea feature flagged you: "Should I have a sleep study?" If blood pressure readings are high: "Can we confirm this with home cuff readings or ambulatory monitoring?"
What to bring. The ECG PDF from Samsung Health if you recorded one, a screenshot of the alert with the date and time, two weeks of resting heart rate and sleep trends, your cuff readings, and a list of medicines, caffeine and alcohol.
What to say, out loud. "My watch flagged [alert] on [dates]. At the time I felt [symptoms]. I know a watch can't diagnose anything, so I'd like to confirm it properly."
If you're brushed off. Ask: "What would make you want to check this further?" and "Can you note in my record that I reported this alert?" That keeps the door open if it happens again.
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How Welltory helps — and what it cannot do
The limits first. Welltory is a general wellness product, not a medical device. It doesn't diagnose arrhythmias, sleep apnea or high blood pressure, and it doesn't replace the regulated features on your watch or a visit to your doctor.
What it can add for a Galaxy Watch 8 owner is a way to read the data as a whole and see your own patterns.
HRV measurements on Galaxy Watch. Welltory supports HRV measurements on Samsung Galaxy Watch4 series and later on Wear OS, including watches on Wear OS 6. You install Welltory on the watch from Menu → Settings → Primary device and can take a manual reading or allow background readings, which happen only when you're calm and still. Free accounts get one manual and one automatic watch measurement a day; Welltory Premium, a paid subscription that renews automatically until you cancel, removes the limit (Samsung watch measurements). Our Galaxy Watch HRV app page shows how it looks.
Sleep Analysis on Android. Welltory reads sleep from Samsung Health and shows a Sleep Score built from sleep balance, schedule, stability and heart rate, plus a suggested bedtime (Sleep Analysis on Android).
A phone camera reading when the watch is charging. You can take a spot HRV and heart rate reading with your phone camera and flash — a short, deliberate measurement, not continuous monitoring (camera measurements).
Tags and patterns. On iPhone, My Patterns asks "What happened?" after a stress or recovery episode so you can tag a cause (My Patterns); on Android, check the app for what's available on your version.
A record for your doctor. From the web app you can export your data as CSV: Dashboard → choose a chart → pick the time range → Export (export guide).
How we made it
We based this article on Samsung's official Galaxy Watch 8 announcements, the Samsung US product page, Samsung's UK support page on Galaxy Watch 8 health features, Samsung's announcements on sleep apnea authorization and US blood pressure monitoring, a polysomnography study of consumer sleep trackers, and a reliability study of skin carotenoid measurement. Device features were checked on November 6, 2026. Search questions came from what people in the United States most often ask about Galaxy Watch 8 features. For the product section, we checked every function against the Welltory Help Center on November 6, 2026.
Made with AI tools, then edited and fact-checked by the Welltory team. See our Editorial & AI policy.
Jane Smorodnikova, co-founder of Welltory, built the methodology behind how we read physiological data.
Written by Tatsiana Yashyna.
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This article is for educational purposes only and is not medical advice. The watch's wellness features are not designed to diagnose or treat any condition. Chest pain, fainting, severe shortness of breath, or a fast or irregular heartbeat with lightheadedness are emergencies: call 911. This guide is published by Welltory, which makes one of the apps mentioned. Welltory is a general wellness product: it helps you track and understand your data and does not diagnose or treat any condition. Sources were retrieved on November 6, 2026.
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Written by Jane Smorodnikova
The founder and CEO of Welltory. A recognized tech leader with two Master's degrees and experience at MIT, she has scaled Welltory to over 17 million users.
Written by Tatsiana Yashyna
Deputy COO at Welltory. With a background in medicine and years of working with health data, she translates research and real physiological signals — sleep, stress, heart rate, and hormones — into clear, evidence-based explanations that help people understand what their bodies are telling them.
References
- Samsung Mobile Press — [Galaxy Unpacked 2025] A first look at the Galaxy Watch8 series: streamlining sleep, exercise and everything in between (July 11, 2025). https://www.samsungmobilepress.com/feature-stories/galaxy-unpacked-2025-a-first-look-at-the-galaxy-watch8-series-streamlining-sleep-exercise-and-everything-in-between
- Samsung Global Newsroom — New features on One UI 8 Watch help users build healthier habits (June 16, 2025). https://news.samsung.com/global/new-features-on-one-ui-8-watch-help-users-build-healthier-habits
- Samsung US — Galaxy Watch8 product page (accessed November 6, 2026). https://www.samsung.com/us/watches/galaxy-watch8/
- Samsung US Newsroom — Samsung's sleep apnea feature on Galaxy Watch first of its kind authorized by US FDA (February 9, 2024). https://news.samsung.com/us/samsung-sleep-apnea-feature-galaxy-watch-first-its-kind-authorized-us-fda
- Samsung Mobile Press — Samsung Health blood pressure monitoring comes to Galaxy Watch in the US (March 31, 2026). https://www.samsungmobilepress.com/articles/samsung-health-blood-pressure-monitoring-us-galaxy-watch
- Samsung US Newsroom — What's new with Galaxy Watch9? (August 6, 2026). https://news.samsung.com/us/
- Chinoy ED, Cuellar JA, Huwa KE, et al. Performance of seven consumer sleep-tracking devices compared with polysomnography. Sleep 2021;44(5):zsaa291. https://doi.org/10.1093/sleep/zsaa291
- Samsung UK Support — Health features on the Galaxy Watch8 and Watch8 Classic (updated September 23, 2025). https://www.samsung.com/uk/support/mobile-devices/health-features-on-the-galaxy-watch8-and-watch8-classic/
- Sisson SB, Helms E, Casperson S, et al. Examining intra- and inter-device reliability of pressure-mediated reflection spectroscopy in a multi-state sample of healthy adults. Public Health Nutrition 2025;28(1):e169. https://www.cambridge.org/core/product/B7F75CA4F34268FAC4C06C82DBDAFDE8/core-reader
- Welltory Help Center — Taking measurements with your Samsung watch. https://help.welltory.com/en/articles/5723878-taking-measurements-with-your-samsung-watch
- Welltory Help Center — Sleep Analysis for Android users (January 23, 2026). https://help.welltory.com/en/articles/12164985
- Welltory Help Center — Taking measurements with your smartphone camera. https://help.welltory.com/en/articles/4412277-taking-measurements-with-your-smartphone-camera
- Welltory Help Center — My Patterns (iOS). https://help.welltory.com/en/articles/16012012-my-patterns-ios
- Welltory Help Center — How to export data from Welltory. https://help.welltory.com/en/articles/3368391-how-to-export-data-from-welltory