# preferredUnits(for:completion:) Returns the user’s preferred units for the given quantity types. ``` func preferredUnits(for quantityTypes: Set, completion: @escaping @Sendable ([HKQuantityType : HKUnit], (any Error)?) -> Void) ``` ## Parameters `quantityTypes` A set of [`HKQuantityType`](/documentation/HealthKit/HKQuantityType) identifiers. These identifiers represent the quantity types to be examined. Before calling this method, your app must request read or share access to all the types in this set. `completion` A block that this method calls as soon as it finishes looking up the preferred units. This block is passed the following parameters: - preferredUnits: If the lookup is successful, this parameter contains a dictionary with `HKQuantityType` identifiers for the keys and [`HKUnit`](/documentation/HealthKit/HKUnit) objects for the values. The keys match those passed to the `quantityTypes` parameter. If an error occurs, this parameter is set to `nil`. - error: An error object. This method returns an error if the preferred units are inaccessible or if your app has not yet requested permission to access the quantity types; otherwise, this parameter is set to `nil`. ## Discussion This method runs asynchronously. As soon as it finishes looking up the preferred units, it calls the completion block on an anonymous background queue. By default, the preferred units are based on the device’s current locale. For example, in the US, the preferred units for the [`bodyMass`](/documentation/HealthKit/HKQuantityTypeIdentifier/bodyMass) identifier are pounds. Other regions may use kilograms or stones. However, users can change their preferred units in the Health app at any time. Your app should present HealthKit data using the current preferred units (see the [`bloodGlucose`](/documentation/HealthKit/HKQuantityTypeIdentifier/bloodGlucose) results identifier for an exception). You should also observe the notification, and update the user interface whenever the user changes his or her preferred units. > Note: > The results returned by this method are based on your app’s permissions: > > - If you have never requested access for a type, this method returns an authorization not determined error. > - If the user denied access to a type, this method returns the default units for the device’s current locale for that type. > - If the user granted either read or share access, this method returns the current preferred units for that type (which may or may not be the default units). --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)