Article

Turning On AFib History Switched Off Your Irregular Rhythm Alerts

Published 5 August 2026 · 7 minute read · by Bryan, developer of My AFib Companion

Your Apple Watch used to tap you on the wrist now and then about an irregular rhythm. Then you were diagnosed with AFib, someone suggested AFib History, and you set it up.

Since then: silence.

You didn’t change a notification setting. You didn’t turn anything off. But the taps stopped, and you’ve been wondering whether the watch is still doing anything at all.

It is. What happened is a setting, not a fault — and it happened on purpose.

Nobody explained this to you, and that isn’t your fault either. Apple documents it in a single sentence, in a bulleted list near the bottom of a support page most people have no reason to open.

What actually happened

Here is the sentence, from Apple’s own support page:

“Since the irregular rhythm notifications feature is not intended for people with AFib, it is turned off automatically when you set up AFib History.”

That’s it. That’s the whole mechanism.

You can confirm it from the other direction, too. On Apple’s page for heart health notifications, one of the listed requirements for turning irregular rhythm notifications on is: “AFib History must not be enabled.”

Two features. The watch runs one or the other. Never both.

What each one actually does

These get talked about as if they’re the same thing. They aren’t, and the difference is the whole point.

Irregular rhythm notifications. In Apple’s words, the feature “will occasionally look at your heartbeat to check for an irregular rhythm that might be suggestive of atrial fibrillation.” It does not fire on the first irregular reading. Apple’s threshold is an irregular rhythm found on five rhythm checks a minimum of 65 minutes apart — so the tap comes at least an hour after the first sign, and often later. Close to the event, then, but not at the moment of it. Apple is also explicit that it only samples, that it collects data when you’re still, and that it “cannot detect all instances of AFib.” It is not intended for people already diagnosed with AFib, or for anyone under 22.

AFib History. This one goes the other way. It doesn’t interrupt you. It estimates the proportion of time your heart showed signs of AFib relative to the time you were wearing the watch, over the previous seven days, and delivers that as a percentage every Monday. It requires a physician diagnosis of AFib, age 22 or over, and — this catches people out — at least 12 hours of wear a day, 5 days a week, to produce estimates consistently.

And Apple says this outright: “AFib History does not notify you when you’re experiencing AFib.”

Why you can’t run both

This is the part I find genuinely interesting, and it’s in Apple’s regulatory paperwork rather than its marketing.

Both features run the same underlying classification algorithm. Apple says so in the AFib History Instructions for Use. What differs is the tuning — and Apple adjusted the AFib History version “to prioritize sensitivity.”

In plain terms: sensitivity is how much of the real thing it catches. Specificity is how well it avoids flagging things that aren’t.

The screening version is tuned to avoid false alarms, because telling someone with no diagnosis that something might be wrong with their heart is a serious thing to get wrong. The burden version is tuned to catch more, because it isn’t alarming anybody — it’s measuring, and undercounting would make the measurement useless.

In Apple’s own validation study, the AFib History tuning came in at 92.6% sensitivity and 98.8% specificity; the notification tuning at 85.5% and 99.6%. Same engine, two settings, opposite priorities.

One algorithm can only be tuned one way at a time. That’s why it’s a choice and not two checkboxes.

Which is worth knowing: the tuning you have now is the more sensitive of the two. It just never tells you in the moment.

What you traded

You gave up a nudge and got a summary.

Before: an occasional tap, close to when something happened, which you could act on — take an ECG, sit down, make a note.

Now: one percentage, on Mondays, describing last week.

I’m going to repeat the important half, because it’s the part people miss. AFib History will not alert you during an episode. Not late, not quietly — not at all. If you have been waiting for your watch to tell you you’re in AFib right now, it isn’t going to, and that is the designed behavior rather than a bug.

Two smaller things that surprise people:

• Your burden will never read 0%. Apple states it displays as “2% or less” instead. A very low week isn’t a zero week, and it isn’t meant to be read as one.
• A blank week is usually a charging schedule. Miss the 12-hours-a-day, 5-days-a-week threshold and you get no estimate. Low Power Mode also switches off the background heart measurements both features depend on.

What you don’t lose: Apple’s documentation attributes the automatic switch-off to the irregular rhythm notification feature only. High and low heart rate notifications are a separate setting, and the ECG app is separate too — you can still take an ECG on demand whenever you feel something.

How to check which one you have on, and how to switch

On your iPhone, in the Health app, tap Search (labeled Browse on older versions of iOS), then Heart. Both features are listed there — AFib History and Irregular Rhythm Notifications — and each will show you whether it’s set up.

To turn irregular rhythm notifications back on, Apple’s documented path is: Health → Search → Heart → Irregular Rhythm Notifications → Set Up, then follow the prompts. Since Apple lists “AFib History must not be enabled” as a requirement, AFib History has to come off first.

Here is where I run out of things I can verify. Apple does not publish a tap path for turning AFib History off. Users report the toggle lives in the Apple Watch app → My Watch → Heart, but I can’t point you at an Apple page that says so, and I’d rather tell you that than guess. Nor does Apple document whether irregular rhythm notifications come back on their own once AFib History is off — assume you’ll need to set them up again.

If you don’t see AFib History at all: the July 2023 Instructions for Use lists Apple Watch Series 4 or later with iPhone 8 or later, and irregular rhythm notifications are only available in certain countries and regions.

Whichever way you go, it’s reversible. This is not a decision you’re locked into.

The one question worth asking your cardiologist

Not “which is better” — that depends on you, and I have no business answering it.

Ask this instead: “Given my situation, would you rather I had the real-time notifications or the weekly burden summary?”

They’ll have a view. It takes thirty seconds of an appointment, and it’s the only version of this question that has a right answer.

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Sources for everything above: Apple Support, “Track your AFib History with Apple Watch” and “Heart health notifications on your Apple Watch” (both published 15 September 2025), plus Apple’s Atrial Fibrillation History Feature Instructions for Use (099-31365, revision K, July 2023) and Irregular Rhythm Notification Feature Instructions for Use. Checked 5 August 2026. Apple changes these features, so if what you’re seeing doesn’t match what’s here, trust your screen and check Apple’s current documentation.

If you keep your own episode log alongside the numbers your watch records, that’s what I build — My AFib Companion, $9.99/month or $59.99/year after a 30-day trial. Nothing in this article needs it.

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