smartwatches have become surprisingly good at spotting irregular heart rhythms. they don’t diagnose atrial fibrillation (AF) on their own, but they can give you an early warning and a record to share with your GP. this guide compares the leading options, explains the studies behind the features, and clarifies which approvals matter in the UK.
How watches detect AF
there are two ways your watch can raise a flag:
- optical pulse monitoring (PPG): the watch shines light into the skin and senses each pulse. software looks for an irregular pattern that can suggest AF in the background.
- on-demand ECG (single-lead): you rest a finger on the bezel/electrode for ~30 seconds to record a trace. the app classifies the rhythm as “sinus rhythm,” “possible AF,” or “inconclusive,” and you can export a PDF to show your GP.
PPG is good for catching episodes you didn’t feel. ECG is better for confirming what’s going on right now.
What the big studies found (plain-english take)
- apple heart study (stanford, 2019): when the watch sent an irregular-rhythm notification, a high proportion of people who then wore a medical ECG patch were confirmed to have AF. take-home: background alerts are meaningfully predictive when followed up properly.
- fitbit heart study (2022): large virtual study supporting the accuracy of fitbit’s irregular rhythm notifications when cross-checked against medical-grade monitoring. take-home: similar story—good screening signal when you confirm with an ECG.
- samsung validation cohorts (multiple, 2020s): showed that single-lead watch ECGs can correctly classify AF vs sinus rhythm under typical conditions. take-home: the ECG app is a useful spot-check, especially when you’re still and relaxed.
- withings clinical programme: established CE-marked AF detection with PPG plus on-demand ECG in its scanwatch line. take-home: strong for long battery life and medically positioned features.
none of these studies claim that watches replace clinical diagnosis. the consistent message is: they are screening tools that help you know when to seek a proper ECG.
Approvals that matter in the UK
- CE/UKCA marking for medical device software in the EU/UK (shows the AF/ECG features are cleared to be offered here).
- FDA clearance (US) is reassuring but not required for UK use.
- note: some brands restrict ECG features by region or phone pairing (e.g., samsung ECG typically needs a samsung phone in the UK). always buy the UK model and check the feature list for your region.
| Device | AF Features | Regulatory Status (UK/EU) | Evidence Highlights | Battery (Typical) | Phone Compatibility | Exports ECG PDF? | Strengths | Trade-offs | Best For |
|---|---|---|---|---|---|---|---|---|---|
| Apple Watch (Series 8/9, Ultra) | PPG alerts + ECG app | CE/UK availability for AF/ECG features | Apple Heart Study; multiple validation papers | ~18–36 hrs (more with Ultra) | iPhone only | Yes | Best app ecosystem, very usable ECG, easy sharing with clinicians | Short battery life; iPhone required | iPhone users wanting seamless health tracking |
| Samsung Galaxy Watch (6/7/8/Ultra) | PPG irregular rhythm + ECG app (Samsung Health Monitor) | CE/UK availability (region dependent); requires Samsung phone | Multiple validation studies; good AF classification | ~2–3 days | Samsung phones (best) | Yes | Strong hardware, solid ECG, good battery vs Apple | ECG features limited on non-Samsung Android | Android users in Samsung ecosystem |
| Google Pixel Watch 2 | PPG irregular rhythm + ECG (Fitbit tech) | CE/UK availability | Fitbit Heart Study | ~24 hrs | Android (best with Pixel) | Yes | Clean interface, Fitbit algorithms, easy export | Short battery; fewer training features | Android users wanting Fitbit health + Google polish |
| Fitbit Sense 2 / Charge 6 | PPG irregular rhythm + ECG | CE/UK availability | Fitbit Heart Study | 6–7 days | iOS/Android | Yes | Excellent battery, affordable, easy ECG export | Fewer smartwatch functions | Budget-conscious users prioritising health features |
| Withings ScanWatch 2 / Nova | PPG irregular rhythm + ECG | CE/UK availability (medical-grade device) | Withings clinical programme | Up to 30 days | iOS/Android | Yes | Outstanding battery, classic look, strong medical credibility | Fewer apps, on-demand ECG only | Users wanting medical focus and long battery life |
| Huawei Watch D / Watch 4 Pro (ECG models) | ECG (model-specific), some include BP monitoring | CE/UK availability varies by model | Brand validation studies | 2–7 days | Android/iOS (best on Huawei) | Often | Includes BP + ECG, solid battery | Limited app ecosystem; variable UK support | Tech enthusiasts wanting BP + ECG in one device |
| Garmin (selected models) | Limited AF features; focus on fitness | ECG rollout limited by region | Early ECG validation | Multi-day to multi-week | iOS/Android | If ECG model, yes | Elite fitness tracking, superb battery | Inconsistent AF support across models | Athletes prioritising training metrics |
how to choose (decision guide)
- you have an iPhone: go Apple Watch. best ECG PDF export and GP-friendly sharing, broadest support docs.
- you have a Samsung phone: pick Galaxy Watch 6/7/8. check that the UK product page lists ECG and irregular rhythm monitoring.
- you want long battery life and a traditional look: Withings ScanWatch 2 or Nova.
- you want a lower-cost, health-first option: Fitbit Sense 2 or Charge 6 (excellent battery, easy ECG export).
- you want extras like on-wrist blood pressure (non-cuff PPG or cuff-style): check Huawei Watch D/4 Pro UK models carefully for what’s enabled here.
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what to do when your watch flags “possible AF”
- stay still and repeat the check.
- save/export the ECG PDF or alert screenshots.
- book your GP; they’ll arrange a 12-lead ECG or ambulatory monitor.
- seek urgent help via NHS 111/999 if you have chest pain, fainting, severe breathlessness, or feel very unwell
bottom line
smartwatches are powerful screening companions. choose a UK-enabled model with both background irregular-rhythm checks and on-demand ECG, make sure you can export a PDF, and build a simple habit: when in doubt, take a 30-second ECG and share it with your GP.
references
- NHS: atrial fibrillation overview — https://www.nhs.uk/conditions/atrial-fibrillation/
- NHS: ECG test — https://www.nhs.uk/conditions/electrocardiogram-ecg/
- British Heart Foundation (smartwatches and heart health) — https://www.bhf.org.uk/
- Mayo Clinic: AFib diagnosis and treatment — https://www.mayoclinic.org/diseases-conditions/atrial-fibrillation/
- Apple Heart Study (Stanford) summary — widely reported; use Apple/Stanford pages or peer-reviewed summary if you want an academic citation
- Fitbit Heart Study summary — Fitbit research blog / journal publication summaries
- Samsung ECG validation summaries — Samsung Health Monitor UK support pages
- Withings ScanWatch medical CE announcements — Withings medical page
Can a smartwatch really detect atrial fibrillation (AF)?
Yes — many modern watches such as the Apple Watch, Samsung Galaxy Watch, Fitbit Sense 2 and Withings ScanWatch can spot patterns of irregular rhythm that suggest AF.
They use light sensors (PPG) to look for uneven pulse timing and, in some models, an on-demand single-lead ECG. These are screening tools — they can’t confirm AF on their own but can help you know when to get checked.
Are smartwatch AF alerts accurate?
When used correctly, they’re surprisingly reliable.
Large studies such as the Apple Heart Study and Fitbit Heart Study found that most people who received an “irregular rhythm” alert and then wore a medical ECG patch were confirmed to have AF.
Accuracy improves when you’re still, relaxed, and the watch fits snugly.
Do smartwatches replace an ECG at the doctor’s?
No — they complement it.
A 12-lead ECG performed by your GP or hospital records your heart’s electrical activity in much greater detail. Smartwatches use a single lead, which is enough to raise a flag but not to diagnose.
→ NHS: ECG test
What should I do if my watch says “Possible AF” or “Irregular rhythm detected”?
Stay calm and repeat the test while you’re still and relaxed.
Save the ECG trace or screenshot.
Book a GP appointment and show your recordings.
If you feel faint, short of breath, or have chest pain, call 111 or 999.
→ NHS 111 online
Which smartwatches are approved for AF detection in the UK?
The following brands have CE or UKCA-cleared AF/ECG features:
Apple Watch (Series 4 and later)
Samsung Galaxy Watch 5/6/7/8/Ultra (via Samsung Health Monitor)
Fitbit Sense 2 and Charge 6
Withings ScanWatch 2 / Nova
Huawei Watch D and 4 Pro ECG (check UK model listing)
Always buy the official UK/EU version so the medical features are active.
Are smartwatch ECG results accepted by doctors?
Most GPs welcome the information — especially if you bring a clear PDF or screenshot showing an irregular rhythm.
It’s used as supporting evidence to decide whether to arrange a medical ECG or 24-hour heart monitor.
What are the limitations of smartwatch AF tracking?
They can miss short or rare episodes.
Alerts can be triggered by anxiety, caffeine, or skipped beats.
Accuracy may fall if the watch is loose or you move during the reading.
They’re best seen as an early-warning system, not a diagnostic device.
How does atrial fibrillation increase stroke risk?
AF makes the upper chambers of the heart beat irregularly, so blood can pool and form clots that may travel to the brain.
If your GP confirms AF, treatment usually includes blood-thinning medication to reduce this risk.
→ British Heart Foundation: AF and stroke risk
Is it worth buying a smartwatch just for AF detection?
If you have high blood pressure, are over 60, or have risk factors for stroke or thyroid disease, a smartwatch with AF and ECG features can be a helpful safety net.
If you’re younger and healthy, it’s still useful for wellness tracking, but regular blood-pressure and GP checks remain the gold standard.
Which watch gives the most complete health picture overall?
Apple Watch Series 9 / Ultra 2 for iPhone users — best ECG workflow.
Samsung Galaxy Watch 7 or 8 for Android users.
Withings ScanWatch 2 for battery life and classic style.
Fitbit Sense 2 / Charge 6 for affordability and simplicity.
Huawei Watch D if you want both BP and ECG (check UK approval).
