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# lowHeartRateEvent

A category sample type for low heart rate events.

```
static let lowHeartRateEvent: HKCategoryTypeIdentifier
```

## Discussion

The system creates [`lowHeartRateEvent`](/documentation/HealthKit/HKCategoryTypeIdentifier/lowHeartRateEvent) samples whenever Apple Watch produces a low heart rate notification. For more information, see [Heart rate notifications on your Apple Watch](https://support.apple.com/en-us/HT208931).

The low heart rate samples are read-only. You can request permission to read the samples using this identifier, but you can’t request authorization to share them. This means you can’t save new low heart rate events to the HealthKit store. To add test data in iOS Simulator, open the Health app and select Browse > Heart > Low Heart Rate Notifications > Add Data.

These samples have a value of [`HKCategoryValue.notApplicable`](/documentation/HealthKit/HKCategoryValue/notApplicable) and include [`HKMetadataKeyHeartRateEventThreshold`](/documentation/HealthKit/HKMetadataKeyHeartRateEventThreshold) metadata.

## Topics

### Metadata Keys

[`let HKMetadataKeyHeartRateEventThreshold: String`](/documentation/HealthKit/HKMetadataKeyHeartRateEventThreshold)

A key that records the threshold of high or low heart rate events in beats per minute.


---

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