What You Can (and Can't) Do With Apple HealthKit Data

If you are building a health or wellness app, Apple Health is probably the first place you look for user data. It sits quietly on every iPhone, collecting information from the Apple Watch and hundreds of connected apps.

At first glance, Apple HealthKit seems like the perfect starting point for health app development. It stores everything in one place. Heart rate, steps, sleep, nutrition, even lab results.

But when you start building, you quickly realize that it's not as simple as it looks. Apple HealthKit is powerful, but it also has clear limits.

In this article, we will break down what you can do with Apple HealthKit data, what you can't, and how to build products that work within those rules or around them.

What Apple HealthKit Actually Is

Apple HealthKit is Apple's developer framework for accessing health and fitness data. It allows apps on iOS to read and write data to the user's Health app in a secure and private way.

Think of it as a local database for the user's body. Every data point gets stored on the iPhone, under the user's control. Steps, heart rate, sleep, workouts all live there.

Apps can request permission to read or write specific data types. For example, your app can read heart rate from the Apple Watch or write nutrition data after a user logs a meal.

Apple designed HealthKit with two main goals. To centralize health data from multiple apps and devices, and to keep that data private and user-controlled.

Those two goals are what make HealthKit so unique and so limited.

What You Can Do With Apple HealthKit Data

Despite its limits, HealthKit is one of the most advanced health data frameworks available. When used correctly, it gives your app access to a huge range of information.

Core health metrics you can access:

• Activity data like steps, distance, flights climbed, energy burned
• Heart metrics including heart rate, HRV, resting and walking averages
• Sleep tracking with time in bed, asleep, sleep stages from Apple Watch
• Body measurements such as weight, BMI, body fat percentage
• Mindfulness minutes from breathing or meditation sessions
• Reproductive health including menstrual cycles, fertility window
• Nutrition data covering calories, macronutrients, vitamins and minerals
• Lab results like cholesterol, glucose, blood pressure when imported

What you can build with this data:

• Personalized dashboards and insights tailored to each user
• AI-driven recommendations based on real health patterns
• Smart goals that adapt based on actual metrics
• Early warning systems for stress or fatigue detection
• Integration with other apps that write to HealthKit

If you are designing a mobile-first health or wellness app, HealthKit can give you everything you need to understand your users within Apple's ecosystem.

What You Can't Do and Why It Matters

Now comes the important part. Apple HealthKit is not a traditional API. It is not a cloud service. It is a local data store on each user's phone.

This design protects privacy but creates serious limitations for developers. Apple built HealthKit around privacy by design principles. In the age of data leaks and algorithmic misuse, Apple chose a path where the user controls their information completely.

The core restrictions you need to understand:

No backend access exists. There is no public server API for Apple Health. You cannot fetch user data directly from your backend or database. All access must happen through the user's iPhone or Apple Watch. This means you must have a native iOS app to read data. The user must install your app and grant permission. You cannot "pull" data from users without their active involvement.

Consent is mandatory for everything. Apple's privacy policy is strict. Every data type requires explicit user consent. Steps, heart rate, sleep each need separate permissions. If the user revokes permission, your app immediately loses access. There are no hidden or background permissions. Everything is transparent, which is good for users but can complicate your data flow design.

Real-time access is limited. HealthKit is not a live stream. You can get new data when the user opens your app or when Apple Health triggers background updates, but not continuously. If you need real-time monitoring for workouts or telehealth use cases, you must integrate directly with the Apple Watch's Workout API, not just HealthKit.

Multi-user scenarios don't work. Apple Health is strictly personal. There is no way to view or manage data for another user through the same device or cloud. This makes multi-user or team dashboards difficult to build unless each user syncs their own data to your backend.

Web-only apps are impossible. Many startups begin with a web-based dashboard and later realize they cannot access HealthKit data from it. Because there is no backend API, your app must run on iOS. You can still have a web dashboard for visualization, but the data must first be collected on the user's phone.

The Mobile-First Reality

Apple Health forces developers to think differently. Instead of connecting to a cloud API, you need an iPhone app that acts as the data gateway.

Here's how it usually works:

1. The user installs your iOS app and gives permission
2. Your app reads selected data from HealthKit
3. With consent, your app uploads it securely to your backend
4. Your backend processes or analyzes the data
5. You present insights back to the user on their phone or web dashboard

This loop works, but it takes engineering effort. You must handle permissions, background sync, and data normalization while maintaining compliance across all of it.

For many early-stage startups, this becomes the bottleneck between idea and product.

Common Developer Challenges

From developer feedback across the healthtech community, a few common themes appear:

Developer Pain PointDescriptionPermission fatigueUsers have to grant access to each data type manuallyTesting complexityHealthKit data can only be tested on real devices, not simulatorsLimited updatesBackground delivery depends on user activityData varietyDifferent apps write to HealthKit differently, creating inconsistenciesAnalytics gapHealthKit gives raw data, not insights

This is why many developers use Apple Health for collection but build additional infrastructure for analytics, AI, and insights.

How to Work Around the Limits

If you understand HealthKit's boundaries, you can design around them smartly.

Build a native app first. Even if your main product is web-based, you need a lightweight iOS app that acts as the data bridge. This app can sync data locally and send it to your backend with user consent.

Normalize and standardize data. HealthKit data types are rich but not uniform. Different apps may log steps, heart rate, or sleep differently. You need ETL processes to make it consistent.

Add context from other sources. Combine HealthKit data with behavioral or environmental data. Calendar events, nutrition logs, or stress questionnaires can add context that wearables cannot capture.

Build transparency into the UX. Show users what data you collect, why, and how you use it. This builds trust and increases the likelihood of long-term data sharing.

Where HealthKit Fits in the Bigger Picture

HealthKit is a great foundation for mobile health data, but it is only one piece of the puzzle. If your users also wear Garmin watches or Oura rings, you will need to combine those data sources too.

That is where developers face the real challenge of integration.

Apple Health, Garmin, Fitbit, Oura, Whoop each has its own API, format, and authentication flow. Bringing them together is the key to creating a complete view of user health.

To move beyond Apple's limits, many companies are now using unified wearable APIs. These platforms connect multiple devices in one integration layer and standardize data across sources.

They solve problems like:

• Different SDKs and data models
• Manual OAuth setup
• Inconsistent metrics
• Long development cycles

Unified APIs make it possible to work with Apple Health data alongside Garmin, Fitbit, Oura, and others all in one format. This is the future of health app development where interoperability doesn't mean complexity.

What Apple Health Can and Can't Do for You

The Opportunity for Health App Builders

Apple HealthKit is not perfect, but it's the foundation of mobile health. It gives developers access to the richest health dataset available on iOS if they design for it properly.

Companies that understand its rules can use it as a competitive edge. They can offer privacy-first experiences, build user trust, and expand into other wearables using unified APIs later.

In the end, HealthKit is not about limits. It's about building responsibly in a space that touches people's most private data.

Start Mobile, Build Unified

Apple HealthKit is both a gift and a challenge. It gives you access to powerful health signals but locks them inside a secure ecosystem.

To use that data at scale, you need a native mobile layer, a secure backend, and a unified data model that can combine multiple devices.

That is the path to building health apps that are not only functional but future-proof.

Ready to make Apple Health work for you? If you are building a health or wellness app and want to understand how to work with Apple HealthKit or how to connect it with other wearables, our team at Momentum can help. Book a Free Consultation →