Apple HealthKit explained: what it tracks and how to use it

Your iPhone has been quietly collecting health data since you first set it up. Steps, sleep, heart rate, medications, even your walking steadiness. It all flows into one app: Apple Health. A framework called Apple HealthKit runs behind the scenes, pulling data from your iPhone’s sensors, your Apple Watch, and hundreds of third-party apps into a single encrypted database on your device.

Most people open the Health app, glance at their step count, and close it. That barely scratches the surface. This guide covers what HealthKit actually collects, how your data stays protected, and how to turn all those numbers into something useful.

What is Apple HealthKit?

Apple HealthKit is the developer framework that powers the Health app on every iPhone. The Health app is the dashboard you see. HealthKit is the engine underneath. Apple introduced both at WWDC in June 2014 alongside iOS 8.

HealthKit acts as a central repository for health and fitness data. It handles communication between your devices, third-party apps, and the Health app itself. Your Apple Watch records your heart rate during a run, and HealthKit stores that data. A nutrition app logs your meals, and HealthKit can share your calorie intake with your workout app so it knows how many calories you’re offsetting with exercise.

HealthKit is not a cloud service. All data lives on your iPhone, encrypted and under your control. Apps must request permission for each specific data type they want to read or write, and you can revoke access at any time.

What data does the Apple Health app collect?

The Health app organizes your data into 14 categories, each covering a different aspect of your health. Here is every category and what falls under it:

Category	Examples of what it tracks
Activity	Steps, distance, flights climbed, exercise minutes, stand hours
Body measurements	Weight, height, BMI, body fat percentage, waist circumference
Cycle tracking	Menstrual periods, symptoms, fertility window, ovulation estimates
Hearing	Headphone audio levels, environmental sound levels, hearing test results
Heart	Heart rate, resting heart rate, HRV, ECG readings, blood oxygen
Medications	Prescriptions, dosages, schedules, drug interaction alerts
Mental wellbeing	Mood logs, state of mind entries, anxiety and depression screenings
Mobility	Walking steadiness, walking speed, step length, double support time
Nutrition	Calories, macronutrients, vitamins, minerals, water intake
Respiratory	Respiratory rate, blood oxygen saturation
Sleep	Time in bed, sleep stages, sleep duration, sleep score
Symptoms	Headaches, fatigue, nausea, dizziness, and dozens more
Vitals	Blood pressure, body temperature, blood glucose
Other data	Time in daylight, handwashing duration, UV exposure

Some of this data is collected automatically. Your iPhone’s motion sensors count your steps, track walking distance, and measure flights climbed without any setup. Pair an Apple Watch and the list grows fast. Heart rate, blood oxygen, wrist temperature, sleep stages, workout metrics, and cardio fitness estimates all flow in continuously.

Other data requires manual entry or third-party devices. Blood pressure needs an external monitor like a Withings BPM Connect. Nutrition data comes from food logging apps like MyFitnessPal. Medications need to be added by hand, though iOS 16 introduced a dedicated tracking feature with reminders and drug interaction warnings.

How does Apple HealthKit protect your privacy?

Apple designed HealthKit around one principle: your health data belongs to you. Here is how the privacy model works in practice.

On-device encryption. HealthKit data is encrypted on your iPhone using the Data Protection class “Protected Unless Open.” When your device locks, the data becomes inaccessible within 10 minutes. It unlocks only when you enter your passcode or authenticate with Face ID or Touch ID.

Granular permissions. Every app must request permission for each data type separately. A workout app might ask to read your heart rate and write workout data. It cannot access your medications or menstrual cycle unless you explicitly allow it. You control reading and writing permissions independently.

No silent data access. If an app doesn’t have read permission for a data type, HealthKit returns empty results rather than an error. The app cannot even tell whether you’re tracking that data type. This prevents apps from inferring your health status based on what you’re tracking.

End-to-end encryption in iCloud. Health data synced to iCloud is encrypted both in transit and at rest. If you use iOS 12 or later with two-factor authentication enabled, your health data is end-to-end encrypted. Not even Apple can read it.

Advertising ban. Apps that access HealthKit data cannot use it for advertising. Apple enforces this through App Store review and developer entitlements. Every app with HealthKit access must also provide a privacy policy that explains how it handles your health data.

According to Apple’s security documentation, Health Records downloaded from healthcare organizations are transferred directly from the institution to your device over a TLS 1.3 encrypted connection. The data does not pass through Apple’s network.

How to set up and use the Apple Health app

Getting started takes a few minutes. These are the features worth setting up first.

Fill in your Health Profile

Open the Health app, tap your profile picture in the upper right corner, then tap Health Details. Add your date of birth, sex, blood type, and skin type. This information helps Apple Watch calculate accurate calorie estimates and personalizes certain health features.

Set up Medical ID

This should be your first priority. Medical ID stores critical information like allergies, medications, blood type, medical conditions, and emergency contacts. First responders can access it from your lock screen without unlocking your phone.

Go to your profile in the Health app, tap Medical ID, then tap Edit. Fill in your details, enable “Show When Locked,” and turn on “Share During Emergency Call.”

Pin your most important metrics

The Summary tab shows your daily health overview. Tap “Edit” next to Pinned to choose which metrics appear at the top. Prioritize the data you actually check: steps, heart rate, sleep, weight, or whatever matters most to you. Everything else stays accessible under the Browse tab.

Connect third-party apps and devices

Go to your profile, then tap Apps under the Privacy section. You’ll see a list of compatible apps already on your phone. Tap each one and toggle the specific data types you want it to share with Health. Limit each app to only the data types it needs.

For external devices like smart scales, blood pressure monitors, or fitness trackers, pair them through the manufacturer’s app first. That app will then ask for HealthKit permission to sync data to Health.

Manage data source priority

Multiple devices tracking the same metric can create conflicts. By default, Health prioritizes data in this order: manually entered data first, then iPhone and Apple Watch data, then third-party apps and Bluetooth devices. You can change this. Open any metric, scroll to “Data Sources & Access,” tap Edit, and drag sources into your preferred order.

How to use Apple Health data for fitness and training

Raw data becomes useful when you watch how it changes over time. The Health app does this automatically through two features: Highlights and Trends.

Highlights surface recent snapshots of your data, like whether you’ve taken more or fewer steps than usual today. Trends track longer patterns across weeks and months. A rising resting heart rate trend might signal accumulated fatigue or poor recovery. An improving sleep duration trend confirms a new bedtime routine is working.

For athletes and active people, the most actionable data points are:

Heart rate variability as a recovery indicator. A reading below your baseline suggests your nervous system is under strain.
Resting heart rate as a long-term fitness marker. It trends downward as cardiovascular fitness improves.
Sleep stages for checking that you’re getting enough deep and REM sleep for physical and cognitive recovery.
Training load on Apple Watch, available in watchOS 11 and later, to balance workout intensity against your recent history.
Cardio fitness as an estimate of your VO2 max. This is one of the strongest predictors of long-term health.

Third-party apps can take this further. Apps like Wildgrow read your HealthKit data and calculate metrics like TRIMP-based training load, readiness scores, and recovery recommendations that the native Health app doesn’t provide.

What apps and devices work with Apple Health?

Hundreds of apps and devices support HealthKit. Here are some of the most popular:

Fitness trackers: Apple Watch, WHOOP, Oura Ring, Garmin (via Garmin Connect), Polar, Coros, Suunto
Smart scales: Withings Body Smart, Wyze Scale, Renpho, Eufy
Blood pressure monitors: Withings BPM Connect, OMRON Evolv
Nutrition apps: MyFitnessPal, Cronometer, Lose It
Workout apps: Strava, Nike Run Club, Strong, Peloton
Mindfulness apps: Calm, Headspace
Medical devices: Continuous glucose monitors, pulse oximeters, smart thermometers

To check if an app supports HealthKit, go to your Health profile, tap Apps, and see what’s listed. If you don’t see an app there, it either doesn’t support HealthKit or hasn’t been configured to share data yet.

The Health app includes two features that extend your data beyond your own device.

Health Sharing lets you share specific metrics with trusted people like a spouse, parent, or coach. Both parties need an iPhone running iOS 15 or later with two-factor authentication enabled. All shared data is end-to-end encrypted through iCloud. You choose exactly which categories to share and can set alerts for heart rate changes or other important events. You can revoke sharing at any time.

Health Records connects the Health app directly to your healthcare provider’s electronic health records system. If your doctor or hospital supports it, you can download lab results, immunizations, allergies, medical conditions, and medication lists directly into the Health app. Apple introduced this feature in 2018 with iOS 11.3, and it’s available at hundreds of participating healthcare organizations in the United States.

Health records are downloaded over an encrypted connection directly from the healthcare institution. The data doesn’t pass through Apple’s servers.

How does Apple Health support medical research?

Apple built two open-source frameworks on top of HealthKit for medical research at scale.

ResearchKit helps researchers create apps that recruit participants and collect data from their iPhones and Apple Watches. Institutions including Stanford University and Johns Hopkins University have used ResearchKit to conduct studies on heart health, women’s health, and other conditions. According to Apple, over 350,000 people contribute to research studies through the Apple Research app.

CareKit helps developers build apps that support patient care beyond the doctor’s office. It enables care plans, symptom tracking, and communication between patients and providers.

Both frameworks have enabled studies that traditional methods could not support. Continuous, passive data collection from Apple Watch gives researchers far more granular data than occasional clinical visits.

Turn your Apple Health data into real insights

Wildgrow reads your HealthKit data and gives you a readiness score, TRIMP-based training load, breathing exercises, and an AI coach. Free on the App Store.

Get Early Access

Frequently asked questions

Do I need an Apple Watch to use the Health app?

No. Your iPhone automatically tracks steps, walking distance, flights climbed, and walking steadiness using built-in motion sensors. An Apple Watch adds heart rate, blood oxygen, sleep stages, ECG, wrist temperature, and workout metrics. The watch expands what the Health app can do significantly, but it’s not required.

Can Apple see my health data?

If you have two-factor authentication enabled and use iOS 12 or later, your health data is end-to-end encrypted in iCloud. Apple cannot access it. Without two-factor authentication, data is still encrypted in transit and at rest, but Apple technically holds the encryption keys. Enable two-factor authentication for maximum privacy.

Is the Apple Health app safe?

Yes. HealthKit data is encrypted on your device and only accessible after authentication with your passcode, Face ID, or Touch ID. Apps cannot access any health data without your explicit permission, and Apple prohibits apps from using HealthKit data for advertising. The primary risk comes from third-party apps: always review their privacy policies before granting access to sensitive data.

How do I export my Apple Health data?

Open the Health app, tap your profile picture, then tap “Export All Health Data.” The app generates a ZIP archive containing your complete health database in XML format. This includes data from all sources: iPhone sensors, Apple Watch, and third-party apps. The export can be large if you’ve been collecting data for years.

What is the difference between Apple Health and HealthKit?

Apple Health is the app you see and interact with on your iPhone. HealthKit is the developer framework running behind it. HealthKit manages data storage, permissions, and communication between apps. When a third-party app reads your step count or writes a workout, it’s using the HealthKit API to talk to the Health app’s database.

Can I share my Apple Health data with my doctor?

Yes, if your healthcare provider participates in Apple’s Health Records program. In the Health app, go to your profile and tap “Medical Records” to search for your provider. For broader sharing, you can also use the Health Sharing feature to share specific categories of data with your doctor. This feature is primarily available in the United States.

Does Apple Health work on iPad?

Yes. Apple brought the Health app to iPad with iPadOS 17 in 2023. It supports the same data categories and can sync data from your iPhone and Apple Watch via iCloud.