Does HRV go down when you're sick?
Usually, yes. When you’re coming down with something, HRV tends to fall while your sleeping heart rate, breathing rate and temperature rise, sometimes days before a positive test. A normal HRV doesn’t rule an illness out.
People hope their ring will warn them before a cold. Sometimes it does. But a low HRV alone could just as easily be last night’s drinks. The useful pattern is several signals moving together, alongside how you feel.
What we’d do: if HRV is down, your sleeping heart rate is up and you feel off, treat it as a sick day coming. Sleep, skip hard training and skip drinks. Test if you need to. Let your symptoms, not the number, decide whether you see a doctor.
What the studies show
| Study | Who | Finding |
|---|---|---|
| Fitbit, 2020 | 2,745 people with COVID-19 | Breathing rate and heart rate went up during illness, and HRV went down |
| Oura, the TemPredict study, 2022 | 63,153 people, 73 with confirmed COVID-19 used to train the model | An algorithm using several signals flagged COVID-19 on average 2.75 days before people sought a test. It caught 82 percent of cases and raised a false alarm on 37 percent of the days people weren’t infected. Adding skin temperature made it better |
| Apple Watch, 2021 | Health care workers in New York | The daily pattern of SDNN changed in the 7 days before a positive test |
Even with several signals combined, more than a third of uninfected days set off the alarm. A low HRV on its own is a weaker sign still, because plenty of low nights have nothing to do with a virus.
When to get help
See a doctor for symptoms, whatever your numbers say. With a pounding or fluttering heartbeat, the US National Library of Medicine says to call emergency services for chest pain, shortness of breath, fainting, unusual sweating or dizziness.
As you recover, wait for your HRV and sleeping heart rate to come back to your usual range before you train hard again.
4 sources
- Natarajan A, Su HW, Heneghan C, Assessment of physiological signs associated with COVID-19 measured using wearable devices, npj Digital Medicine, 2020pubmed.ncbi.nlm.nih.gov
- Mason AE et al., Detection of COVID-19 using multimodal data from a wearable device: results from the first TemPredict Study, Scientific Reports, 2022pubmed.ncbi.nlm.nih.gov
- Hirten RP et al., Use of physiological data from a wearable device to identify SARS-CoV-2 infection and symptoms and predict COVID-19 diagnosis, Journal of Medical Internet Research, 2021pubmed.ncbi.nlm.nih.gov
- MedlinePlus, Heart palpitations, US National Library of Medicine, checked 2026-11-10medlineplus.gov
