Does Fitbit record HRV values over 150ms?

[JBraddock]

I have had the Inspire 3 for about 14 days now. More often than not, I do not receive a Heart Rate Variability (HRV) value. It says "No data in the past 24 hours".

Every other metric is there. My sleep is sufficiently long. The watch is sufficiently tight. I have only had 4 HRV values out of 13 nights.

One thing to note is that three of these measurements came after days of intense exercise/poor sleep the night prior.

My lowest HRV measurement (97ms) was after a night of drinking. My other three measurements were 146ms, 147ms and 149ms.

I am wondering if Fitbit doesn't report HRV values over a certain threshold (say 150ms)? Because most nights I am greeted with the 'No data in the past 24 hours' message and it is very frustrating. HRV is one of the stats I am interested in the most and my device is not recording it.

Any ideas?

[JBraddock]

Anybody 😅?

[Bill_209]

I don't know if there is an upper limit for HRV measurements, but you will definitely not get a HRV measurement returned if you don't get sleep stages returned on the Sleep tile, by design.

[JBraddock]

It's weird, I am seeing sleep stages on all of 'sleeps'. But rarely an HRV.

[LZeeW]

Hello @JBraddock and welcome to the Community.  Fitbit doesn't have an HRV range limit listed in any published documentation.  It posts limits in other features.  For example, the ECG will be inconclusive if your heart rate is less than 50 bpm or greater than 120 bpm.  Features that give an SpO2 value can't report a value <80%.

Support might have an answer for you.  When users don't see an HRV, Support will tell you to make sure you are wearing your Fitbit tight enough while sleeping.  You need detailed beat-to-beat heart rate data to calculate HRV.  Try limiting your question just to the detected range.  IMO, it should report and HRV over 150 msec.  While uncommon, it's not abnormal.