Heart Rate Accuracy Issues with Fenix 8

Sounds like you need to tighten the watch to be quite snug and have it sit high on the wrist (away from your wrist bone) in order to get an good reading. It needs to sit flush with no light leakage between the sensor and skin.

Most casual users tend to wear their watches like a bracelet with it loose rotating around. This won't yield accurate readings.

As I’ve mentioned before. If you’re really concerned about the accuracy run wrist and strap measurement at the same time. Go out and do whatever you do to get heart rate up. Download to express and have a look. If they are significantly different call Garmin support. Easier to get resolved if you have facts and it is for the same activity. 

@RosscoP I think this makes most sense.
Best is to make screenshots of identical activities with and without strap measurement and send them to Garmin support for analysis.

Hey Patten67. There is a connectIQ app that lets you run the wrist HR and strap at the same time. It records both with an activity and Garmin  connect will display both for the activity. (On PC anyway) also you can view both on Garmin Basecamp and can look at the heart rate throughout activity. I ran it on my old F6 and now my E3. On the F6 the wrist recording ran a constant 8 seconds behind the chest strap. On the E3 I recorded an 8 hour hike, with plenty of  climbs. For me the watch and strap were pretty much beat for beat.  I can’t remember what it’s called but I will let you know when I get home tonight. 

Ok. Pretty sure the Connect IQ app you want is “Ant+ HRM heart rate monitor “ by “flocsy”.

Install it. Within what ever app you are using, “Hike” etc, add this as a data field. I set it up next to the wrist (watch) Hrm for instant comparison. When you upload completed activity to connect or Basecamp you can see BOTH recordings side by side. Brilliant. 
Then you’ll have a good idea of how accurate, or not, your watch Hrm is. I’m lucky I guess as the E3 I have appears pretty accurate. 
Well worth it for peace of mind or to get your watch fixed if there is an issue. And much easier to sort out with direct comparison. 
Good luck

I agree. Attempted troubleshooting on my own as recommended. Contacted chat support where I was told to try troubleshooting.... This is beyond frustrating as my HR is often 50+ BPM off. I have an old Polar that still works. Seems it is time to switch.

Same here, mine seems accurate, but delayed, like it is taking an average. It seems like something that could be fixed in firmware.

The same thing happened to me, very disappointed with the Fenix ​​8. I've had it under warranty for a week now, so you can see what the problem is. When I'm not active, the heart rate goes to 75, and when I look at the actual heart rate, it drops to 25. When I sleep, I have constant peaks of 75 heart rates. This didn't happen to me on my Epix Gen 2.

The Fenix 8 AMOLED was a “upgrade” from my Fenix 5, a watch which literally saved my life by detecting an abnormal heart rhythm.

But the Fenix 8 is giving wildly inaccurate heart rate monitoring.

I was doing a warm up yesterday wearing F5 and F8, the F5 was giving a heart rate of 85ish, the F8 192!
Checking my pulse, it was 80ish.
Swapped the wrists with the watches and the problem followed the F8.

 Whilst the screen is great, the key features I need to work are really poor.

Many in this post have reported low readings.  I have seen the opposite at 20-30bpm higher jump.  For example: on an easy run at 120-130BPM after 45minutes it jumps to 145-155bpm for the next 45minutes.  I’m 60YO so max HR is about 163bpm.  13.1 race at 45min jumps from 145 to 180. Unfortunately, unusable without HR strap now.  Forerunner 945 and EPIX never had this issue.

Hopefully this is fixed with an update.