AutoSleep. 
Health Check. 

Problem 7. 

What’s happening here is that your Watch is not capturing background heart rate data at certain times. It’s the Watch itself that does this, not the app. 

If interested, you can verify the existence of this problem as follows: 

iOS 12:

  1. Go into Apple Health app. It has a white icon with a red heart. 
  2. Select health data tab. 
  3. Select vitals - not heart, vitals. Yes it's confusing. 
  4. Select heart rate.
  5. Select show all data option below the graph.
  6. Select last night. 
  7. This will now show all the heart rate readings that the watch has captured for the day. 
  8. Scroll to the period that you were asleep. You should see heart rate readings every 2-10 minutes. You will find that some readings are missing. 

iOS 13:

  1. Go into Apple Health app. It has a white icon with a red heart. 
  2. Tap Browse tab twice. 
  3. Tap Heart.
  4. Tap Heart Rate.
  5. Scroll all the way to the bottom. 
  6. Select Show all data.
  7. Select last night. 
  8. This will now show all the heart rate readings that the watch has captured for the day. 
  9. Scroll to the period that you were asleep. You should see heart rate readings every 2-10 minutes. You will find that some readings are missing. 


There are two common reasons for this: 

1) Passcode & Wrist Detection.

You need to have a passcode on your Watch & wrist detection enabled. Otherwise your Watch will not capture background heart rate due to Apple privacy settings. You need to enter the passcode when you put the Watch on your wrist. 

You can add a passcode by going into the Apple “Watch” app on your iPhone, then turn on passcode and turn on wrist detection. 

If you also enable the “unlock with iPhone” option this means you can use Touch ID to auto enter the passcode for you. You do not need to enter it again until you take the Watch off your wrist. 

Do you have a tattoo?  This often prevents the heart rate sensor from working. 

Are you wearing a Milanese loop or Stainless Steel band? These have poor skin contact & can prevent the heart rate sensor from working properly.

Make sure that the Watch is not too loose, so that it loses contact with the skin during sleep. Make sure it is worn above the wrist bones (closer to elbow). These will also stop the heart rate from being captured. 


2) WatchOS Problem / Health Synch Probs

If both of these are ok, then it is usually a crashed WatchOS service that causes this. 

Often you can solve problems like this by powering the iPhone and Watch off and on as per these links. i.e. Shut down completely and restart. 

iPhone: https://support.apple.com/en-au/HT201559

Watch: https://support.apple.com/en-au/HT204510



Once you have solved this problem, you will find an option to disable 'system error'. This will let you use whatever data was captured, though keep in mind there will be some incorrect readings.