The Apple Watch Vitals app checks five overnight readings (heart rate, respiratory rate, wrist temperature, blood oxygen, and sleep duration) against your own typical range and flags any that fall outside it as outliers. One outlier on its own is common and usually has an everyday cause, like a drink with dinner, a hot bedroom, or a loose band. Two or more on the same night are more likely to mean something has changed, which is why Apple sends a notification the next morning when that happens. Apple names elevation changes, alcohol, medications, and illness as possible causes. Vitals is a wellness tool, not a diagnosis, so look at the night in context and check how you feel.
What Is the Apple Watch Vitals App?
Apple added the Vitals app in watchOS 11, released in September 2024. It gives you a quick read on how your body looked overnight and highlights any metric that is outside your usual range. Apple says the out-of-range classifications and notifications come from an algorithm developed with real-world data from the Apple Heart and Movement Study (Apple).
To get readings, Apple asks you to set up sleep with Track Sleep with Apple Watch turned on, use Sleep Focus, and wear your watch to bed. Fit matters: if the watch is too loose, the sensors might not capture accurate readings (Apple).
On the watch, open the Vitals app to see last night's metrics, and tap the calendar button for the last 7 days. On iPhone or iPad, open Vitals in the Health app for day, week, month, or 6-month views. The Metrics view there shows how many outliers each metric had, and the States view shows which days were High, Typical, or Low.
If you have Apple Watch Series 12 or Apple Watch Ultra 4, heart rate variability (HRV) replaces sleep duration in the overnight view, and a daytime view adds resting heart rate and HRV.
The Five Metrics in the Vitals App
All five are measured while you sleep, and each is compared with your own typical range.
| Metric | What it measures | Common reasons it moves |
|---|---|---|
| Heart rate | Your heart rate while asleep | Alcohol, late hard workouts, stress, illness |
| Respiratory rate | Breaths per minute while asleep | Hard training, heat, altitude, respiratory infections |
| Wrist temperature | Skin temperature at the wrist during sleep | Alcohol, room temperature, menstrual cycle, illness |
| Blood oxygen | The share of your blood's hemoglobin carrying oxygen | Altitude, congestion, breathing disruptions, watch fit |
| Sleep duration | Total time asleep | Late nights, early alarms, travel |
Overnight Heart Rate
Sleeping heart rate is fairly stable for most people, which is why a change in it stands out. It runs higher after alcohol, a late hard workout, a stressful day, or when you're coming down with something. A sustained drop over weeks of consistent training is often a sign of improving fitness. The resting heart rate glossary covers what's normal and what moves it.
Respiratory Rate
Your breathing rate during sleep is controlled automatically and stays consistent from night to night, so even a modest rise stands out. Hard training, heat, high altitude, and respiratory infections can all push it up. See respiratory rate for typical values.
Wrist Temperature
Apple lists wrist temperature in the Vitals app for Apple Watch Series 8 or later and every Apple Watch Ultra. Apple Watch SE 3 also measures it during sleep. Apple Watch sets your wrist temperature baseline after about five nights, and the Health app shows each night as a change from that baseline. Apple lists alcohol, your sleep environment, diet and exercise, menstrual cycles, and illness as things that can shift it (Apple). More in our wrist temperature guide.
Blood Oxygen
Blood oxygen (SpO2) sits in a narrow band for most healthy people at sea level, so it rarely moves much from night to night. Altitude, congestion, and breathing disruptions during sleep can lower it, and so can a poorly positioned watch.
Not every watch shows it in Vitals. Apple Watch SE doesn't support the Blood Oxygen app. On US models bought on or after January 18, 2024 with part numbers ending in LW/A or LS/A, the Blood Oxygen analysis runs on your iPhone, the results appear in the Health app, and Blood Oxygen isn't available in the Vitals app (Apple; Apple Newsroom).
Sleep Duration
Sleep duration is how long you slept, compared with your usual. A short night is an easy outlier to explain, and it often explains outliers in other metrics too. For context, sleep experts recommend that adults get 7 or more hours per night on a regular basis (Watson et al., 2015). FITIV's Sleep score looks at the quality of that time as well as the length.
How Apple Sets Your Typical Range
Apple asks you to wear your watch to sleep for 7 days to establish your typical range (Apple). After that, each night's readings are compared with your own range for each metric, and anything outside it counts as an outlier. Apple doesn't publish how it calculates your typical range or where it draws the line for an outlier.
A personal range matters because normal varies so much from person to person.
A reading that is perfectly ordinary for your partner could be unusual for you. That's why the Vitals app compares each reading with your own typical range rather than a population average.
What One Outlier in the Vitals App Means
One outlier on its own is rarely a concern. Your body doesn't run the same way every night, and plenty of ordinary things nudge a single metric. Say you had two glasses of wine at a friend's birthday dinner, and the next morning Vitals flags your heart rate as high. That outlier is just the wine showing up in your data.
Alcohol can also shift your wrist temperature, and so can a warm room or heavy bedding. A short night shows up as a sleep duration outlier by itself. A late, hard workout can keep your heart rate up for the first part of the night: in a sleep-lab study of 11 fit adults, heart rate during sleep was higher after exhausting cycling that ended about two hours before bed (54 vs 51 bpm), especially in the first three hours (Myllymäki et al., 2011). Apple calls out medications as another cause, and a loose band can produce readings that don't reflect your body at all.
Short-term swings happen even without an obvious cause. In the same 92,457-person study, 20% of people had at least one week in which their resting heart rate moved by 10 bpm or more (Quer et al., 2020).
So before you worry about a single outlier, think about what was different about yesterday. If you can name the cause, you're done. If you can't, watch the next few nights. A one-off that goes back to typical is just noise.
What Two or More Outliers Can Mean
By default, Apple Watch notifies you the next morning when at least two of your overnight metrics are outside your typical range (Apple). Apple says the changes may be linked to "elevation changes, alcohol consumption, or even illness" (Apple), and its support page adds medications to that list.
Clusters are more meaningful because the common causes tend to move several metrics at once. If you wake up to a notification that your heart rate and wrist temperature were both out of range, the useful question is what could have moved both at the same time.
Illness
When your body fights an infection, signals like resting heart rate, breathing rate, and temperature can shift, sometimes before you feel sick. Research on consumer wearables has found these changes in several studies:
- In a smartwatch study of people who caught COVID-19, 26 of 32 (81%) showed changes in heart rate, daily steps, or time asleep, and 22 of 25 with symptom data showed those changes at or before symptom onset (Mishra et al., 2020).
- A model built on nighttime respiratory rate flagged 80% of COVID-positive cases by the third day of symptoms (Miller et al., 2020).
- In a study of 63,153 Oura Ring wearers, adding continuous temperature made a COVID-19 detection algorithm more accurate, though the algorithm was trained on just 73 confirmed cases (Mason et al., 2022).
These were research algorithms, not the Vitals app, and none of them is a test for any illness. What they show is why several changes on the same night are worth noticing.
Alcohol
Alcohol is one of the most reliable ways to create a cluster. In a real-world study of 4,098 Finnish employees, alcohol raised heart rate and lowered heart rate variability during the first three hours of sleep in a dose-dependent way, with measurable effects even at low intake (Pietilä et al., 2018). Add a warmer wrist and a shorter or more broken night, and two outliers the morning after a few drinks is no surprise.
Travel and Elevation
A trip can stack several outliers at once. At higher elevation there's less oxygen in the air, so blood oxygen tends to dip and breathing rate can rise while your body adjusts. Long flights, new time zones, and an unfamiliar bed can shorten your sleep and raise your sleeping heart rate on top of that. If your outliers line up with a trip and you feel fine, give them a few nights to settle before reading more into them.
Hard Training
A big training block, a race, or a much harder week than usual can raise sleeping heart rate and breathing rate for a night or two. On its own that's a normal response to training stress. What matters is whether it settles. Outliers that persist through easier days, alongside poor sleep or feeling flat, are a reason to back off. Our recovery guide covers how to read those signals together.
Other Everyday Causes
Two outliers can also come from two unrelated things on the same night, such as a short night plus a hot bedroom. Wrist temperature also shifts across the menstrual cycle, so a temperature outlier can line up with a normal part of your cycle.
When to See a Doctor About Vitals Outliers
Apple is clear that Vitals app measurements are not intended for medical use, and it advises talking with your healthcare provider before making health decisions based on them (Apple). The app can tell you something changed; it can't tell you why.
Consider checking in with a doctor if:
- Outliers come with symptoms, such as fever, a cough, unusual fatigue, dizziness, or heart palpitations.
- The same metrics stay out of range for several nights and you can't link them to alcohol, travel, training, or your cycle.
- Blood oxygen readings stay low, especially if you also feel short of breath, snore heavily, or wake up gasping.
- You have a heart or lung condition, or take medication that affects heart rate or breathing, and your numbers change from your usual pattern.
Don't wait for your watch if you feel seriously unwell. Chest pain, severe shortness of breath, or fainting need urgent medical care whatever the Vitals app says. A night with no outliers doesn't rule anything out, either.
If you're sick and wondering whether to train, our guide to exercising when you're sick covers when rest is the better choice.
How FITIV Puts Your Overnight Vitals in Context
FITIV Pulse reads the same kinds of overnight data your watch saves to Apple Health and puts it next to your training. Its Overnight Vitals feature tracks five metrics, read by default from your main sleep of the night: resting heart rate, HRV, respiratory rate, blood oxygen, and wrist temperature. Sleep duration is covered separately by your Sleep score.
Like the Vitals app, FITIV judges each metric against your own typical range, built from your recent history:
- Vitals card: the Today tab shows last night's value for each metric, labeled Typical, Above, Below, Well Above, or Well Below.
- Vitals Summary: each metric shows your typical range, 7-day and 30-day averages, and how many outliers you've had in the last 30 days, with a 30-day chart that marks your typical range.
- Recovery: your vitals and Sleep score feed your Recovery score, one number you can use to plan the day's training.
FITIV shows wrist temperature as an actual reading in °F or °C rather than a change from baseline, so it looks different from Apple's Health app even though it comes from the same data.
FITIV doesn't send notifications about your vitals and doesn't try to detect illness. It's built for fitness tracking and general wellness, so if your readings concern you, the advice is the same as with the Vitals app: talk to a healthcare professional.
Apple Watch, iPhone, iPad, watchOS, and Apple Health are trademarks of Apple Inc. Oura is a trademark of Oura Health Oy. Other product names are trademarks of their respective owners. FITIV is an independent app and has not been authorized, sponsored, or otherwise approved by Apple Inc. FITIV is not affiliated with or endorsed by the other companies mentioned.
Frequently Asked Questions
Why is my Apple Watch Vitals app not showing any data?
The Vitals app needs Track Sleep with Apple Watch and Sleep Focus turned on, and you need to wear your watch to sleep for 7 days before it sets your typical range. A loose fit or a watch that ran out of battery overnight can also leave gaps.
Why doesn't my Vitals app show blood oxygen?
Apple Watch SE doesn't support the Blood Oxygen app. On US models bought on or after January 18, 2024 with part numbers ending in LW/A or LS/A, Blood Oxygen is analyzed on your iPhone and shown in the Health app instead of the Vitals app. Availability also varies by region.
How do I turn off Vitals app notifications?
On your Apple Watch, open Settings, tap Vitals, and turn Notifications off. You'll still see your outliers in the Vitals app and the Health app; you just won't get a morning alert when two or more metrics are out of range.
Can the Apple Watch Vitals app detect illness?
Not as a diagnosis. Apple says Vitals measurements are not intended for medical use. Several outliers on the same night can be linked to illness, but they can also come from alcohol, elevation changes, or medications, so talk to a doctor if you have symptoms or the pattern continues.
Does the Vitals app show heart rate variability?
Only on Apple Watch Series 12 and Apple Watch Ultra 4, where HRV replaces sleep duration in the overnight view. Other Apple Watch models still record HRV in the Health app, and apps like FITIV include it with your other overnight vitals.
