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Documentation Index

Fetch the complete documentation index at: https://mintlify.com/kingstinct/react-native-healthkit/llms.txt

Use this file to discover all available pages before exploring further.

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Overview

The useMostRecentQuantitySample hook fetches the most recent sample for a given quantity type and automatically subscribes to updates, ensuring your component always displays the latest data.

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Usage

import { useMostRecentQuantitySample } from '@kingstinct/react-native-healthkit';

const sample = useMostRecentQuantitySample('HKQuantityTypeIdentifierStepCount');

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Parameters

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identifier
QuantityTypeIdentifier
required
The HealthKit quantity type identifier (e.g., 'HKQuantityTypeIdentifierStepCount')
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unit
string
Optional unit for the quantity. Defaults to the user’s preferred unit.

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Return Value

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sample
QuantitySample | undefined
The most recent quantity sample, or undefined if no data is available yet.
interface QuantitySample {
  uuid: string;
  quantity: number;
  unit: string;
  startDate: Date;
  endDate: Date;
  metadata?: Record<string, unknown>;
}

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Example: Display Step Count

import { useMostRecentQuantitySample } from '@kingstinct/react-native-healthkit';
import { View, Text } from 'react-native';

function StepCounter() {
  const stepSample = useMostRecentQuantitySample('HKQuantityTypeIdentifierStepCount');

  if (!stepSample) {
    return <Text>Loading steps...</Text>;
  }

  return (
    <View>
      <Text style={{ fontSize: 24, fontWeight: 'bold' }}>
        {stepSample.quantity.toLocaleString()} {stepSample.unit}
      </Text>
      <Text style={{ color: 'gray' }}>
        Last updated: {stepSample.endDate.toLocaleString()}
      </Text>
    </View>
  );
}

​
Example: Custom Unit

import { useMostRecentQuantitySample } from '@kingstinct/react-native-healthkit';
import { View, Text } from 'react-native';

function BodyFatPercentage() {
  // Explicitly request percentage unit
  const sample = useMostRecentQuantitySample(
    'HKQuantityTypeIdentifierBodyFatPercentage',
    '%'
  );

  if (!sample) {
    return <Text>No body fat data available</Text>;
  }

  return (
    <View>
      <Text>Body Fat: {sample.quantity}%</Text>
      <Text>Measured: {sample.startDate.toLocaleDateString()}</Text>
    </View>
  );
}

​
Example: Multiple Quantities

import { useMostRecentQuantitySample } from '@kingstinct/react-native-healthkit';
import { View, Text, StyleSheet } from 'react-native';

function HealthDashboard() {
  const steps = useMostRecentQuantitySample('HKQuantityTypeIdentifierStepCount');
  const heartRate = useMostRecentQuantitySample('HKQuantityTypeIdentifierHeartRate');
  const bloodGlucose = useMostRecentQuantitySample(
    'HKQuantityTypeIdentifierBloodGlucose',
    'mg/dL'
  );

  return (
    <View style={styles.container}>
      <View style={styles.card}>
        <Text style={styles.label}>Steps</Text>
        <Text style={styles.value}>
          {steps?.quantity.toLocaleString() || '--'}
        </Text>
      </View>
      
      <View style={styles.card}>
        <Text style={styles.label}>Heart Rate</Text>
        <Text style={styles.value}>
          {heartRate ? `${heartRate.quantity} ${heartRate.unit}` : '--'}
        </Text>
      </View>
      
      <View style={styles.card}>
        <Text style={styles.label}>Blood Glucose</Text>
        <Text style={styles.value}>
          {bloodGlucose ? `${bloodGlucose.quantity} ${bloodGlucose.unit}` : '--'}
        </Text>
      </View>
    </View>
  );
}

const styles = StyleSheet.create({
  container: { padding: 20, gap: 15 },
  card: { padding: 15, backgroundColor: '#f5f5f5', borderRadius: 8 },
  label: { fontSize: 14, color: '#666' },
  value: { fontSize: 24, fontWeight: 'bold', marginTop: 5 }
});

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Example: With Metadata

import { useMostRecentQuantitySample } from '@kingstinct/react-native-healthkit';
import { View, Text } from 'react-native';

function InsulinDelivery() {
  const sample = useMostRecentQuantitySample(
    'HKQuantityTypeIdentifierInsulinDelivery',
    'IU'
  );

  if (!sample) {
    return <Text>No insulin delivery data</Text>;
  }

  // Access metadata if available
  const reason = sample.metadata?.HKInsulinDeliveryReason;

  return (
    <View>
      <Text>Insulin: {sample.quantity} {sample.unit}</Text>
      <Text>Reason: {reason || 'Unknown'}</Text>
      <Text>Time: {sample.startDate.toLocaleTimeString()}</Text>
    </View>
  );
}

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Auto-Updates

The hook automatically subscribes to changes for the specified quantity type. When new data is saved to HealthKit, the component will re-render with the updated value. 
import { 
  useMostRecentQuantitySample,
  saveQuantitySample 
} from '@kingstinct/react-native-healthkit';
import { View, Text, Button } from 'react-native';

function LiveStepCounter() {
  const steps = useMostRecentQuantitySample('HKQuantityTypeIdentifierStepCount');

  const addSteps = async () => {
    // Save new steps - the hook will automatically update
    await saveQuantitySample(
      'HKQuantityTypeIdentifierStepCount',
      'count',
      100,
      { startDate: new Date(), endDate: new Date() }
    );
  };

  return (
    <View>
      <Text>Steps: {steps?.quantity || 0}</Text>
      <Button title="Add 100 Steps" onPress={addSteps} />
    </View>
  );
}

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Important Notes

Ensure authorization before using this hook. The app will crash if you haven’t requested authorization for the quantity type. Use useHealthkitAuthorization or requestAuthorization first.
// ✅ Correct: Request authorization first
const [authStatus, request] = useHealthkitAuthorization({
  toRead: ['HKQuantityTypeIdentifierStepCount']
});

const steps = authStatus === 'unnecessary' 
  ? useMostRecentQuantitySample('HKQuantityTypeIdentifierStepCount')
  : undefined;

// ❌ Wrong: Will crash if not authorized
const steps = useMostRecentQuantitySample('HKQuantityTypeIdentifierStepCount');

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See Also