How to read your Fitbit HRV

We have not verified from Fitbit’s own pages which HRV formula or time window the Fitbit app uses, or how its readiness score is built, so we do not label them here.

Whatever the label, compare a night with your own usual range over several weeks. A single night up or down says little on its own.

HRV type: Not confirmed from official pages.

Compare a night with your own usual range over the last weeks, not with another person or another device. A single low night is most often a reaction to something specific — a short night, alcohol, an infection, stress or hard training. Several days below your range together with a higher resting heart rate and feeling unwell are a reason to rest.

Scores such as Readiness, Recovery, Nightly Recharge or HRV Status are each maker’s own algorithm. Two devices on the same night can show different HRV numbers because they measure at different times and with different formulas; neither is “wrong”.

Google says the Google Health API is not onboarding new projects at this time, and the older Fitbit Web API is being shut down on 2026-10-30. So a direct connection is not possible for us right now.

Through Apple Health

We have not confirmed that Fitbit writes HRV to Apple Health, so we do not promise that your Fitbit HRV will appear in ONDA. If your device is not Apple Watch, ONDA can still measure your pulse with the iPhone camera, along with a breathing-rate estimate. The camera gives pulse, not HRV.