Install HRV Flow on your iPhone
Download from the App Store.
2
Grant HealthKit permissions
Allow access to health data on first launch. This is required for reading HRV, heart rate, and sleep data.
3
Confirm the Apple Watch app
The Apple Watch app installs automatically when you install the iPhone app. Check in the Watch app under "My Watch."
4
Wait for baseline learning
The iPhone app analyzes your historical HRV data from Apple Watch to calculate your personal baseline. This takes just seconds if sufficient data is available.
Wearing your Apple Watch regularly helps accumulate HRV data, enabling more accurate stress detection over time.
❓ Frequently Asked Questions
A daily score from 0 to 100 that represents your morning condition. It's calculated from three factors:
Resting Heart Rate (25%): Lower is generally better
Sleep Duration (25%): 7-8 hours is optimal
The score is personalized to your own baseline using your historical data (accuracy improves with 3+ days of data).
Yes, that's completely normal. Your score fluctuates based on sleep quality, previous day's activity, stress levels, alcohol consumption, and more. What matters is the trend over a week, not a single day's number. Check the 7-day chart in the Condition tab to see your trends.
HRV measures the variation in time intervals between heartbeats. When you're stressed or fatigued, HRV tends to be lower. When relaxed, HRV tends to be higher. Apple Watch measures this automatically, and HRV Flow uses this data to assess your stress levels.
Apple Watch is required for HRV monitoring and real-time stress detection. Breathing exercises can be tried on iPhone, but heart rate feedback requires running them on Apple Watch.
iPhone: iOS 17.0 or later
Apple Watch: watchOS 10.0 or later
All health data is stored only on your device and iCloud. No data is ever sent to our servers. See our Privacy Policy for details.
HRV Flow sends three types of notifications:
Morning condition: Your condition score and day-over-day comparison upon waking
Stress alerts: When Apple Watch detects a drop in HRV
Scheduled reminders: Breathing exercise reminders at your chosen times
Notifications are automatically suppressed during sleep. Morning condition alerts can be toggled on/off and the notification time can be changed in the Settings tab.
We offer 11 breathing patterns for different purposes: relaxation, focus, emergencies, and sleep. All patterns are available for free.
Choose based on your goal:
Beginners: Start with "Simple Deep Breathing"
Feeling stressed: "4-7-8 Breathing" or "Physiological Sigh" work well
Improving focus: Try "Box Breathing"
Improving HRV: "Coherent Breathing" is scientifically recommended
Better sleep: Try "Sleep Breathing"
Acute stress: "SOS Breathing" helps you calm down quickly
You can see details for each pattern in the breathing list on your Apple Watch.
Yes. You can display real-time HRV values and stress levels on your Apple Watch face. Circular, rectangular, and inline complications are supported.
Method 1: From Apple Watch
1
Long press on the watch face
2
Tap "Edit"
3
Tap on a complication slot
4
Turn the Digital Crown to select "HRV Flow"
Method 2: From iPhone Watch app
1
Open the "Watch" app on your iPhone
2
Tap the watch face you want to edit under "My Faces"
3
Select a slot under "Complications"
4
Choose "HRV Flow"
The HRV value on the complication updates automatically whenever Apple Watch captures new HRV data (typically every 10-30 minutes). Available complication types vary by watch face.
Yes. Breathing sessions completed on Apple Watch are automatically synced to your iPhone within minutes. They will be reflected in the Habits tab for streak tracking and statistics.
HRV Flow is designed to minimize battery consumption.
HRV monitoring: Simply receives data from Apple Watch's regular HRV measurements (every 10-30 minutes) — no additional sensor activity
Complications: Event-driven updates only when new HRV data arrives
During breathing sessions: Runs as a workout session, using battery similar to any workout app
Under normal use, the impact on Apple Watch's daily battery life is minimal.
HRV Flow calculates a "Personal Baseline" from your historical HRV data and compares your current HRV against it to assess stress in 4 levels:
😌 Relaxed: HRV is above your baseline
🟢 Normal: HRV is near your baseline
🟡 Elevated: HRV is below your baseline
🔴 High: HRV is significantly below your baseline
Time-of-day and day-of-week patterns are also considered, so the same HRV value may receive different assessments in the morning versus evening.
Yes. Tap any pattern in the Breathing tab to try it on iPhone with a countdown timer and phase display. For heart rate feedback, run the exercise on Apple Watch.
Recommendations are based on time of day and stress level. Morning suggests simple breathing, daytime suggests box breathing for focus, and evening suggests relaxation patterns. When stress is elevated, quick-relief patterns are prioritized.
🔧 Troubleshooting
The personal baseline is calculated on your iPhone and synced to Apple Watch via iCloud. If it's not syncing:
1
Open the iPhone app and check if the baseline is calculated in the HRV tab
2
In the iPhone app, go to Settings tab → tap "Sync to Watch"
3
On Apple Watch, tap the "Sync from iPhone" button
Baseline calculation requires sufficient HRV data. Try wearing your Apple Watch for a few days before checking again. Make sure both devices are signed in to the same iCloud account.
1
Open the "Watch" app on your iPhone
2
Scroll down to "Available Apps" and find HRV Flow
3
Tap "Install"
Automatic app installation may be disabled. Check: Watch app → General → Automatic App Install is turned on. Installation works best when your Apple Watch is nearby, charging, or connected to Wi-Fi.
Check iPhone Settings → Notifications → HRV Flow is enabled
Check Apple Watch Settings → Notifications → HRV Flow is enabled
Make sure Focus Mode or Do Not Disturb is not active
Confirm your Apple Watch is being worn and collecting HRV data
Verify HealthKit permissions: iPhone Settings → Health → Data Access & Devices → HRV Flow
Make sure your Apple Watch fits snugly on your wrist
HRV data is measured automatically by Apple Watch (typically every 10-30 minutes)
During breathing exercises, a workout session keeps the app active. However, screen behavior depends on your Apple Watch model:
Series 5 and later (Always On Display): The screen dims when you lower your wrist but remains visible
SE / Series 4 and earlier (no Always On Display): The screen turns off when you lower your wrist. Raise your wrist or tap the screen to wake it
In both cases, haptic (vibration) guidance continues even when the screen is off. You can follow the breathing rhythm by vibration alone without watching the screen.
If a status code appears on the result screen, refer to the guide below:
W-AUTH (Workout write permission not granted)
1
On iPhone, go to Settings → Health → Data Access & Devices → HRV Flow
2
Under "Allow to Write", turn on "Workouts"
3
Run a breathing session on Apple Watch again
If the "Allow to Write" section is not visible at all, delete HRV Flow from Apple Watch and reinstall it from the Watch app on iPhone.
W-START (Could not start workout session)
Restart your Apple Watch and try again
Make sure no other workouts are currently running
W-HR (Heart rate not detected)
Make sure your Apple Watch fits snugly on your wrist
Clean the back of the Watch (sensor area) if needed
Very short sessions (e.g., Quick 3-0-3) may finish before the heart rate sensor fully starts. Try a longer pattern
W-REQ (Permission check failed)
Restart your Apple Watch and try again
Make sure both devices are signed in to the same iCloud account
Confirm both devices are connected to the internet (Wi-Fi or mobile data)
Check that workout reading and writing are enabled: iPhone Settings → Health → Data Access & Devices → HRV Flow
Opening the iPhone app will automatically import any unsynced sessions
Syncing usually takes a few minutes, but may take longer depending on network conditions. Wait a moment and try reopening the iPhone app.
ℹ️ About
HRV Flow is completely free with all features included. No ads.
This is an optional setting that helps us improve the app by collecting anonymous data about which features are used. Health data such as HRV and heart rate is never sent. All features work without consent, and you can toggle it on/off anytime in settings.
📩 Contact Us
If you couldn't find a solution above, please don't hesitate to reach out. We typically respond within 1-2 business days.
⚠️ For your privacy, please do not include specific health data such as HRV values or heart rate in your inquiries. Your email address will be used solely for responding to your message.