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# gramUnit(with:)

Returns a HealthKit unit for measuring mass, using gram units with the provided prefix.

```
class func gramUnit(with prefix: HKMetricPrefix) -> Self
```

## Parameters

`prefix`

A valid metric prefix value. For the complete list of prefix values, see [`HKMetricPrefix`](/documentation/HealthKit/HKMetricPrefix).

## Return Value

A HealthKit unit for measuring mass based on grams and the given prefix.

## Discussion

This method is used to create prefixed versions of grams, typically kilogram units, as shown below.

```objc
HKUnit *kg = [HKUnit gramUnitWithMetricPrefix:HKMetricPrefixKilo];
```

---

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