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Smartwatches have come a long way from when they used to just count your steps and measure heart rate—now, your Apple Watch could provide some early warning that you might not feel up to hitting that step goal soon. Apple recently rolled out the Vitals App for the Apple Watch that monitors your breathing, temperature, and heart rate overnight. Since the release, Apple Watch users are sharing that the watch alerted them that their vitals were out of the norm before they even thought they were sick.

Now that fall illnesses, including COVID-19, are in full swing, users are sharing across social media that their watch clocked abnormal breathing rates and elevated temperatures days before they later came down with full-blown cold symptoms. “The Vitals App knew I was sick 3 days before I did,” posted one Redditor. Others in the thread report other watches with blood oxygen, heart rate, and temperature sensors have done the same.

Apple Watch screenshots showing multiple views of the "Vitals" app screen, including heart rate. — Photo: Apple

This smartwatch premonition has been going on for some time; users have been noting that “the Apple Watch knew I [had] COVID before I knew” for at least three years, since the device rolled out a wrist temperature feature with the Apple Watch Series 8. Researchers have also been studying this ability, and finding it to be an accurate early warning for COVID and other illnesses, since 2021.

The Vitals App, available with the latest watchOS 11 on Apple Watch Series 8 models and later, is particularly useful as it gives a comprehensive picture of multiple metrics and will even send notifications of irregularities. And the number of stories popping up points to its potential as a cold and flu season tool.

X user Rory Evans posted that his Series 9 picked up some irregularities in his vitals days before testing positive for COVID, calling the tool “clever and very useful tech to have—especially in such a fast paced world.” X user Emanuel Job Ayo posted a screenshot showing Vitals “outliers” and called it “wild” that the app could “detect and warn before you even fall sick.”

Other Reddit users reported the app showed outliers after they had their COVID vaccines, and some even saw the effects of having a bit too much to drink. X user Valerie Polad posted that she was “incredibly impressed” with the Vitals App: “My watch told me that a few metrics were unusually high this morning and that the underlying cause may be illness. And here I am with my fever a few hours later!”

As your watch gets to know your biometric data, like your typical temperature, breathing rate, and even how many hours of shut eye you get per night, it knows your normal ranges. So while your typical sleeping heart rate isn’t a particularly useful data point on its own, the combo of metrics can show when something is off—and help you tune into your body and potentially seek medical attention.

Unfortunately, blood oxygen (a key indicator of COVID) is not one of the metrics Vitals tracks in the U.S. Apple had to remove light-based pulse oximetry sensors from the Apple Watch after courts found that it violated another wearable technology company’s patent, and watches sold with the feature overseas are banned from being sold in the U.S.

Apple told Well+Good they could not officially comment on the anecdotes, but it’s worth noting the watch was recently FDA approved for sleep apnea, another condition where any advance warning can help be proactive about health. Apple also partnered with researchers to use Apple Watch blood oxygen data to study COVID in the very first year of the pandemic. When it comes to fighting viruses, information—and early warning—is power.