Apple Watch AFib History estimates the percentage of time a person with a physician-diagnosed atrial fibrillation (AFib) condition showed pulse patterns consistent with AFib during prior wear. It is a retrospective, periodic trend measure—not a live alarm, a diagnosis, or a replacement for prescribed monitoring and treatment.
What the FDA actually cleared
On June 3, 2022, the FDA granted 510(k) clearance to Apple’s Atrial Fibrillation History Feature under submission K213971. The FDA record classifies it as “Photoplethysmograph Analysis Software for Over-the-Counter Use” in the cardiovascular category and found it substantially equivalent to a legally marketed predicate device. See the FDA 510(k) record and clearance letter.
That is FDA clearance of software, not blanket FDA approval of every Apple Watch model or a finding that the watch is a universal AFib diagnostic device. Apple introduced the feature with watchOS 9 in September 2022; availability depends on model, region, language, iPhone, and supported software (Apple’s watchOS 9 announcement).
How AFib History works
The watch’s optical sensor shines green LEDs into the skin and uses photodiodes to detect blood-flow changes at the wrist. This photoplethysmography (PPG) data provides pulse timing. AFib History periodically analyzes irregular pulse intervals that may be consistent with AFib, then calculates a retrospective estimate of AFib burden—the approximate proportion of monitored time showing those patterns. It analyzes data collected while the watch is being worn; it is not continuously displaying a diagnosis or recording every heartbeat.
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- A FULL-FEATURED HEALTH TRACKER—Apple Watch Series 11 gives you invaluable insights about your body, right from your wrist. Take an ECG anytime* and get alerts for a high and low heart rate or an irregular rhythm*—so you can stay closer to your heart. You can also view your overnight health tracking metrics with the Vitals app* and be notified of possible sleep apnea.*
- KNOW YOUR SLEEP SCORE—With advanced sleep tracking, Series 11 gives you a daily sleep score. It’s an easy way to help measure and understand the quality of your sleep, so you can make it more restorative.
- GET HYPERTENSION NOTIFICATIONS—Did you know that Series 11 can spot signs of chronic high blood pressure? By analyzing how your blood vessels respond to beats of the heart, it can notify you of possible hypertension.*
- SAFETY FEATURES—A smartwatch that puts your safety first. Series 11 can detect a hard fall or severe car crash, automatically help connect you with emergency services, and notify your emergency contacts.* Check In can automatically notify a loved one when you’ve arrived at your destination.
- A POWERFUL FITNESS TRACKER—With advanced metrics and motivating features like Pacer, Heart Rate Zones, training load, and Workout Buddy powered by Apple Intelligence from your nearby iPhone*—Series 11 is made to help everyone stay active, from runners and hikers to strength-training enthusiasts.
Apple presents the result as a weekly percentage and longer-term history in the Health app. The feature does not identify every episode, and “signs consistent with AFib” are not proof that AFib occurred.
Who is eligible
- You must be 22 or older.
- A physician must have diagnosed you with AFib.
- You need a compatible Apple Watch and iPhone with supported software. Apple’s original launch requirement was Apple Watch Series 4 or later (including Apple Watch SE) paired with an iPhone 8 or later or iPhone SE (second generation or later) running iOS 16; current compatibility should be checked against Apple’s support page.
- Heart Rate and Wrist Detection must be enabled, and the watch must collect enough usable data.
Apple recommends wearing the watch at least 12 hours per day on five days per week for consistent estimates (current Apple Support instructions). AFib History is not the same as Irregular Rhythm Notifications: the latter is generally intended for people without a known AFib diagnosis. Turning on AFib History automatically turns off Irregular Rhythm Notifications.
How to turn it on
Menu names can vary slightly by region, language, and software release. On a compatible iPhone:
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- A FULL-FEATURED HEALTH TRACKER—Apple Watch Series 11 gives you invaluable insights about your body, right from your wrist. Take an ECG anytime* and get alerts for a high and low heart rate or an irregular rhythm*—so you can stay closer to your heart. You can also view your overnight health tracking metrics with the Vitals app* and be notified of possible sleep apnea.*
- KNOW YOUR SLEEP SCORE—With advanced sleep tracking, Series 11 gives you a daily sleep score. It’s an easy way to help measure and understand the quality of your sleep, so you can make it more restorative.
- GET HYPERTENSION NOTIFICATIONS—Did you know that Series 11 can spot signs of chronic high blood pressure? By analyzing how your blood vessels respond to beats of the heart, it can notify you of possible hypertension.*
- SAFETY FEATURES—A smartwatch that puts your safety first. Series 11 can detect a hard fall or severe car crash, automatically help connect you with emergency services, and notify your emergency contacts.* Check In can automatically notify a loved one when you’ve arrived at your destination.
- A POWERFUL FITNESS TRACKER—With advanced metrics and motivating features like Pacer, Heart Rate Zones, training load, and Workout Buddy powered by Apple Intelligence from your nearby iPhone*—Series 11 is made to help everyone stay active, from runners and hikers to strength-training enthusiasts.
- Open the Health app.
- Tap Search, then Heart.
- Tap AFib History.
- Tap Set Up, then Get Started.
- Enter your date of birth and confirm that a doctor diagnosed your AFib.
- Complete the remaining on-screen instructions.
If AFib History is missing, first update the iPhone and watch to their latest compatible software and verify the model, region, age, diagnosis confirmation, Heart Rate, and Wrist Detection settings. Do not try to bypass the eligibility flow; contact Apple Support or your clinician if the requirements are met but the option remains unavailable.
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- A weekly estimated AFib-burden percentage and notifications when enough data has been collected.
- Longer-term history that can be reviewed with a clinician.
- Comparisons with recorded factors such as sleep, exercise, and alcohol consumption.
- AFib History Highlights after about six weeks of sufficient readings.
- A PDF export you can share with a physician.
Why the result may say “2% or less”
Apple does not display exactly 0% for AFib History. Results at the low end appear as “2% or less.” That category is not necessarily exactly 2%, and it is not proof that no AFib occurred. It means the estimate falls within Apple’s lowest displayed range.
AFib History, ECG, and Irregular Rhythm Notifications compared
| Feature | Sensor and timing | Intended use | Alerts and output | Main limitation |
|---|---|---|---|---|
| AFib History | Passive, periodic optical PPG analysis | Trend monitoring for people already diagnosed with AFib | Retrospective weekly burden estimate; no episode-by-episode alert | May miss episodes and depends on sufficient wear and usable pulse data |
| ECG app | User-initiated electrical recording by touching the Digital Crown | A single-lead rhythm strip in supported circumstances | Classifies a recording, such as AFib or sinus rhythm, when possible | Not continuous; not a substitute for a physician’s diagnosis |
| Irregular Rhythm Notifications | Periodic optical pulse analysis | Generally for users without a known AFib diagnosis | Notification when an irregular pattern is detected; not a burden history | Not designed to find every episode or provide a definitive diagnosis |
Apple reports the ECG app’s clinical testing showed 98.3% sensitivity for AFib classification and 99.6% specificity for sinus-rhythm classification among classifiable recordings in an approximately 600-subject trial (Apple ECG support). Those figures apply to the ECG app—not AFib History—and must not be used as AFib History accuracy figures.
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- KEEP HELP CLOSE AT HAND—SE 3 is a smartwatch that can detect a hard fall or severe car crash and automatically help connect you to emergency services and notify your emergency contacts.* Check In can automatically notify a loved one when you’ve arrived at your destination.
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It is not a real-time AFib alert
AFib History checks periodically and reports a historical estimate. Apple says it does not notify you while you are experiencing AFib and may not identify every irregular-rhythm instance. A normal or low weekly percentage therefore cannot rule out an episode happening now.
Why data can be missing or misleading
A low or absent estimate can reflect inadequate data rather than absence of AFib. Apple’s Instructions for Use and support guidance identify these factors:
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- Too little wear time, charging gaps, or a loose or poorly positioned watch.
- Motion or hand and finger movement during measurement.
- Cold temperatures or reduced skin blood flow.
- Dark tattoos in the sensor area.
- Low Power Mode, which can disable background heart measurements.
- Environmental conditions or strong electromagnetic fields.
- Other rhythms with a regular pattern, including atrial flutter or atrial tachycardia, that may not produce the irregular pattern the feature is designed to recognize.
If there is no weekly estimate
- Check that the watch was worn about 12 hours on at least five days that week.
- Confirm Heart Rate and Wrist Detection are enabled.
- Check whether Low Power Mode was active or the watch spent long periods charging.
- Refit the watch snugly and allow more wear time for usable readings.
If the percentage rises
Do not change anticoagulants, antiarrhythmics, or other treatment based on the watch alone. Save or export the trend and discuss a persistent increase with your clinician, particularly if symptoms are present.
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- GET SMARTER HEALTH INSIGHTS—Apple Watch SE 3 is an advanced health tracker that helps you better understand your body. The smartwatch sends alerts for an irregular heart rhythm, or an unusually high or low heart rate.* You can view your overnight health tracking metrics with the Vitals app,* track your sleep score, and get sleep apnea notifications.*
- A GREAT FITNESS TRACKER—SE 3 can track your workouts in a healthy number of ways—from running and strength training to simply achieving your 10K steps a day. With real-time metrics and Workout Buddy powered by Apple Intelligence from your nearby iPhone,* you’ll hit your goals like never before.
- KEEP HELP CLOSE AT HAND—SE 3 is a smartwatch that can detect a hard fall or severe car crash and automatically help connect you to emergency services and notify your emergency contacts.* Check In can automatically notify a loved one when you’ve arrived at your destination.
- WOMEN’S HEALTH INSIGHTS—SE 3 has advanced sensors that track your wrist temperature while you sleep. With this smartwatch, you can log your periods and symptoms, get period predictions, and get notified of cycle deviations.*
- GREAT BATTERY LIFE AND FASTER CHARGING—Enjoy a smartwatch with all-day, 18-hour battery life* from sunup to sundown. Then charge up to twice as fast as SE 2* and get up to 8 hours of battery in just 15 minutes.*
What the 2024 FDA MDDT qualification means
In 2024, the FDA qualified AFib History as a Medical Device Development Tool (MDDT). That designation allows its weekly estimates to be used as a biomarker in defined clinical-study settings, including studies comparing AFib burden before and after cardiac-ablation treatment (FDA evidence summary).
MDDT qualification does not make every consumer reading a diagnosis, replace a clinical ECG, prove that an ablation worked, or authorize medication changes from the percentage alone.
When it is useful—and when it is not
Potentially useful
- Following changes in estimated burden over time.
- Giving a cardiologist additional longitudinal information.
- Comparing trends with recorded lifestyle factors.
- Supporting a discussion about treatment response.
Poor fit
- Screening yourself for AFib without a prior physician diagnosis.
- Expecting an immediate warning during an episode.
- Being unable to wear the watch regularly.
- Needing formal, continuous, or clinician-interpreted ambulatory ECG monitoring.
- Trying to evaluate rhythms outside the feature’s intended AFib pattern.
When to seek medical help
Use AFib History as information to discuss with your care team, not as a reason to start, stop, or alter treatment. Apple says the watch cannot detect a heart attack or stroke. Chest pain, pressure, tightness, severe shortness of breath, fainting, or other suspected emergency symptoms require emergency medical attention, regardless of the displayed percentage.
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- A FULL-FEATURED HEALTH TRACKER—Apple Watch Series 11 gives you invaluable insights about your body, right from your wrist. Take an ECG anytime* and get alerts for a high and low heart rate or an irregular rhythm*—so you can stay closer to your heart. You can also view your overnight health tracking metrics with the Vitals app* and be notified of possible sleep apnea.*
- KNOW YOUR SLEEP SCORE—With advanced sleep tracking, Series 11 gives you a daily sleep score. It’s an easy way to help measure and understand the quality of your sleep, so you can make it more restorative.
- GET HYPERTENSION NOTIFICATIONS—Did you know that Series 11 can spot signs of chronic high blood pressure? By analyzing how your blood vessels respond to beats of the heart, it can notify you of possible hypertension.*
- SAFETY FEATURES—A smartwatch that puts your safety first. Series 11 can detect a hard fall or severe car crash, automatically help connect you with emergency services, and notify your emergency contacts.* Check In can automatically notify a loved one when you’ve arrived at your destination.
- A POWERFUL FITNESS TRACKER—With advanced metrics and motivating features like Pacer, Heart Rate Zones, training load, and Workout Buddy powered by Apple Intelligence from your nearby iPhone*—Series 11 is made to help everyone stay active, from runners and hikers to strength-training enthusiasts.
Buying considerations
If you want the feature, confirm the exact watch-and-iPhone compatibility and supported watchOS before buying. Apple’s official purchase page is apple.com/shop/buy-watch; Apple Certified Refurbished models are listed at apple.com/shop/refurbished/watch. Refurbished buyers should verify battery condition, return terms, software support, and regional health-feature availability. Cellular service is not inherently required for AFib History, although it may matter for other uses.
A dedicated on-demand ECG product such as KardiaMobile may suit someone whose clinician wants user-initiated rhythm strips; see AliveCor’s current product page for supported models and terms. Prescribed ambulatory ECG monitoring remains the appropriate route when a clinician needs continuous or near-continuous recording, symptom correlation, or a formal interpreted report. These options are not interchangeable with AFib History.
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