---
title: HKMetadataKeyMenstrualCycleStart
framework: healthkit
role: symbol
role_heading: Global Variable
path: healthkit/hkmetadatakeymenstrualcyclestart
---

# HKMetadataKeyMenstrualCycleStart

A key that indicates whether the sample represents the start of a menstrual cycle. This metadata key is required for menstrualFlow category samples.

## Declaration

```swift
let HKMetadataKeyMenstrualCycleStart: String
```

## Discussion

Discussion Set this key’s value to true if the sample represents the start of a menstrual cycle; otherwise, set it to false.