If you regularly wear an Apple Watch, you've probably discovered the apps most useful to your daily life, like responding to emails and texts, checking the weather and using Apple Pay for contactless payments. But there are host of health apps and features that might not currently be on your radar, and they have the potential to be life-saving.

I spoke with Dr. Lauren Cheung, a doctor at Apple, who reviewed the hidden health features on the Apple Watch and why they were created.

1. The Vitals app for sleep and more

Using overnight health metrics, the Vitals app can reveal much about your health and how it changes day to day. From heart rate and wrist temperature (available on Apple Watch Series 8 or later and any Apple Watch Ultra model) to respiratory rate and sleep duration, you can get a thorough picture of your health from just one glance at your watch.

"When two or more of your metrics are out of range, we will notify you with information about why that might be," Cheung explained. "How it works is just after you wake up, you might see a notification from the Vitals app. For example, maybe your heart rate and wrist temperature were high -- this could be due to illness or alcohol consumption."

With the health information from the Vitals app, you can make informed decisions about your health. If specific metrics are outside your normal range, you can choose to get extra rest that day or visit your doctor if you have particular symptoms. 

How to set up the Vitals app

To set up your typical range, you must wear your Apple Watch for at least seven days. Ensure your watch is not loose on your wrist; otherwise, it might not capture accurate readings. 

To set up notifications, go to Settings on your Apple Watch, tap Vitals and turn on notifications. 

For sleep specifically, make sure Track Sleep with Apple Watch is set up and Sleep Focus is enabled. To do so, open your iPhone's Health app, tap Get Started under Set Up Sleep, tap Next and then follow the on-screen prompts. You can also use your Apple Watch's Sleep app and follow the on-screen instructions. 

2. Noise notifications 

You can use the Noise app on your Apple Watch to measure the sound levels in your environment. You can also enable noise notifications, so your watch can tell you when you're exposed to dangerously loud sounds. 

When asked why noise notifications were added to the Apple Watch, Cheung said, "The world can be loud, and we believe it's important for you to be educated and empowered about how your environment, and the noise around you, can impact your hearing health over time. That way, you can take action; whether that's moving to a quieter space or popping in AirPods Pro 2 with Hearing Protection."

With the AirPods Pro 2 or 3, Apple also offers a Hearing Test that can give you a baseline for your hearing health and help you adjust accordingly. Or you can even use your AirPods Pro 2 as a hearing aid. 

How to set up Noise notifications

Simply go to the Watch app on your iPhone, tap My Watch, tap Noise, tap Noise Threshold and then pick a decibel level. Different limits are listed based on World Health Organization recommendations. 

3. Ovulation estimates 

"The technology is pretty remarkable," Cheung said. "We created new temperature-sensing capabilities on Apple Watch that help you understand nightly changes from your baseline temperature, which can be caused by exercise, jet lag or even illness. The unique two-sensor design improves accuracy by reducing bias from the outside environment, detecting changes as small as 0.1 degrees Celsius."

With the Apple Watch Series 8 or later and all Apple Watch Ultra models, this technology allows the Cycle Tracking app to estimate when ovulation occurs. "The reason we can do that is because after you ovulate, there is a biphasic shift, or in other words, an increase in temperature in response to changing hormones," Cheung said. This can also help improve the Cycle Tracking app's period predictions.

How to set up ovulation estimates

First, set up Cycle Tracking with fertility predictions enabled and no ongoing cycle factors logged. To do so, open your iPhone or iPad's Health app, tap Browse on the iPhone or open the iPad's sidebar, tap Cycle Tracking, tap Get Started and follow the on-screen instructions. 

You will also want to ensure you set up Track Sleep with your Apple Watch and have Sleep Focus enabled for at least 4 hours per night for five nights. To set up Sleep, follow the instructions in your Apple Watch's Sleep app. 

4. Fall detection 

Many Apple Watch users have reported the benefits of fall detection, said Cheung. "For those who have an active lifestyle, they can choose to enable it during workouts -- the feature is able to recognize the unique motion and impact of falls from a bike and other workout types," she said.

If your watch detects a hard fall, it will sound an alarm, display an alert and tap you on the wrist. With the alert, you can either dismiss it by tapping "I'm OK" or contact emergency services. The watch automatically calls if you've been immobile for around a minute. After, it will message your emergency contacts with your location. If you don't have cellular or Wi-Fi coverage, Fall Detection may reach emergency services via the Emergency SOS via satellite system (if available). 

Note that Apple Watch can't detect all falls and may mistake a high-impact activity as a fall. 

How to set up fall detection 

To enable it, on your iPhone, open the Watch app, tap My Watch, tap Emergency SOS and turn Fall Detection on or off. If enabled, you can choose whether you want it to always be on or only during workouts. This works for Apple Watch SE, Apple Watch Series 4 or later and Apple Watch Ultra or later, and if you inputted your age when you set up your Apple Watch or in the Health app, the Fall Detection feature turns on automatically if you're 55 or older.

5. Heart health notifications for atrial fibrillation

For those with Apple Watch Series 1 or later and people aged 13 and over, you can have your Apple Watch alert you if your heart rate is high or low, or if it has an irregular rhythm.

"For the most part, you don't have to do anything besides turn them on," Cheung said. "They work passively in the background as you live your day. If your heart rate is unusually high or low, you can get a notification, so you can take action. And if your heart rhythm shows signs of atrial fibrillation -- an irregular heart rhythm -- you'll receive a notification."

Cheung said atrial fibrillation as the most common type of arrhythmia among adults, which can have serious side effects on your health if not treated. "For instance, it's the leading cause of stroke," she said. "And some people with AFib can have little to no symptoms, so they may not even realize they're experiencing episodes and ultimately may not seek attention."

If you get an irregular rhythm notification, you can speak with your doctor and even share a PDF that includes information about your heart health notifications and, if you take one, your electrocardiogram. Available on Apple Watch Series 4 or later and all Apple Watch Ultra models, the ECG app allows you to take a test that records the timing and strength of the electrical signals that make your heartbeat.

How to set up heart health notifications

To set up heart rate notifications, go to the Apple Watch app on your iPhone, tap My Watch, tap Heart, tap High Heart Rate and choose Beats Per Minute, tap Low Heart Rate and choose a BPM. For irregular rhythm notifications, open your iPhone's Health app, tap Browse, tap Heart, tap Irregular Rhythm Notifications and enable them. 

6. Time in daylight

Your Apple Watch's ambient light sensor can automatically estimate your time in daylight. If you manage a family member's Apple Watch, you can also see how much time they spend in daylight. 

"There are a few reasons it's important to be aware of how much time in daylight you're getting," Cheung said. "For adults, research shows that spending around 20 minutes outdoors every day has both physical and mental health benefits, including providing essential vitamin D and even boosting your mood."

Time in daylight is crucial for kids' vision health. "The International Myopia Institute recommends children spend 80-120 minutes outside each day to help lower their risk of myopia, or nearsightedness," she said. 

How to set up time in daylight

Start by making sure that Motion Calibration & Distance is turned on. You can do so in the iPhone's Settings app. Tap Privacy & Security, tap Location Services, turn on Location Services, tap System Services and ensure that Motion Calibration & Distance is on. 

To view your time in daylight, go to your iPhone's Health app, tap Browse, tap Other Data and then tap Time in Daylight. 

7. State of mind to log your mood

You can log your emotions and daily moods in the Mindfulness app on your Apple Watch, which can help you identify your feelings and notice patterns in your mental health. From the app, you can also take time for a Reflect or Breathe session, which can tell you more about your heart rate once complete. 

"Emotional awareness and regulation is an important element of mental health and we're happy to be introducing tools and resources for our users across the world," Cheung said. "One of the tools we introduced is State of Mind, which can help tremendously in a few ways. First, the act of using it can create benefits for your mental well-being in and of itself. Second, it can help you identify important insights and trends on what might be contributing to your state of mind so you can take action. And third, it can encourage you to check in with yourself using depression or anxiety assessments in the Health app."

Cheung added that taking the time to identify our feelings can help us control how we respond to our moods and emotions. This can positively affect our health and, over time, allow us to build resilience. 

How to set up State of Mind

In your Apple Watch's Mindfulness app, tap State of Mind and then tap Get Started if it's your first time using it. From here, you can log how you feel in the moment or how you've felt overall that day. To see your history and patterns over time, open your iPhone's Health app, tap Browse, tap Mental Wellbeing, tap State of Mind and tap Show in Charts. From there, you can also view how your State of Mind relates to your sleep, exercise, time spent in daylight and mindful minutes.

8. Sleep apnea notifications 

"Sleep apnea is a prevalent disorder where breathing momentarily stops during sleep, preventing the body from getting enough oxygen," Cheung said. "It's estimated that sleep apnea impacts more than 1 billion people worldwide and, in most cases, goes undiagnosed. If left untreated, it can have important health consequences over time, including increased risk of hypertension, type 2 diabetes and cardiac issues."

If your Apple Watch detects elevated breathing disturbances while you sleep for over 30 days, you will receive a sleep apnea notification. From there, you can create a PDF that shows when sleep apnea may have occurred, along with three months of breathing disturbance data and more, which you can then share with your doctor to discuss the next steps. 

This feature is available on the Apple Watch Series 9 or later or Apple Watch Ultra 2 or later. Just make sure you have the latest version of WatchOS and iOS. Note that this feature is intended for people aged 18 or older who have not already been diagnosed with sleep apnea. 

How to set up sleep apnea notifications

Make sure Sleep is set up. On your iPhone, open the Health app, tap Get Started under Set Up Sleep, tap Next and follow the on-screen steps. Then, wear your Apple Watch to bed for at least 10 nights over 30 days. 

To turn on sleep apnea notifications, open the Health app on your iPhone, tap Browse, tap Respiratory, tap Set Up under Sleep Apnea Notifications, tap Next and then follow the on-screen instructions. Under Respiratory, you can also view your sleep apnea notifications and breathing disturbances.

9. Handwashing 

With Handwashing, the Apple Watch Series 4 and later can detect when you begin washing your hands and time you until you reach the recommended 20-second duration. The US Centers for Disease Control and Prevention also recommends this as the minimum amount of time. If you stop washing your hands before 20 seconds, your watch will encourage you to keep going. It can even remind you to wash your hands whenever you return home. 

"We wanted to find a way to help our users of all ages track their time spent washing their hands, especially during a time when it was particularly important early in the pandemic, so we introduced the feature in 2020," Cheung said. "The approach uses machine learning models to determine motion which appears to be handwashing, and then uses audio to confirm the sound of running water or squishing soap on your hands."

How to set up handwashing

On your Apple Watch, open Settings, tap Handwashing and turn on the Handwashing Timer. You can do the same on a managed Apple Watch and set up handwashing reminders.