What does a low HRV mean?

The short answer

A low HRV reading most often means your body is carrying a bit more load than usual. That can follow something ordinary, such as a short night, alcohol, a hard session or a busy week. One low morning is common and rarely worth worrying about. A drop that lasts for days, or comes with symptoms, deserves more attention.

“Low” only makes sense compared with your own usual. Harvard Health says there is no recommended HRV value, because it varies so much between people, and it notes that HRV changes constantly through the day and from day to day. If you are new to the measure, start with what HRV is, and see what is a good HRV for how widely healthy numbers range.

Everyday causes of a low reading

• Alcohol. In a study of 4,098 Finnish employees who wore heart monitors, Pietilä and colleagues found that alcohol shifted the body away from rest during the first three hours of sleep, and that the effect grew with the dose. It showed up even at low intake.
• Poor or short sleep. Cleveland Clinic lists lower quality or amount of sleep among the things that lower HRV, and Harvard Health lists poor sleep as one of the habits that can disrupt the balance. There is more on how much sleep you need.
• Hard training. A tough session can leave HRV lower for a while. Stanley and colleagues describe the heart’s return to a calmer state after exercise as taking anywhere from minutes to around two days, and as very individual. A review of endurance athletes by Bellenger and colleagues also found that resting HRV was largely unaffected by overreaching, so a low reading is not proof that you are overdoing it.
• Illness. The British Heart Foundation lists infection and fever among the things that change heart rate. In a study of health care workers wearing Apple Watches, Hirten and colleagues found that HRV patterns differed in the week before and the week after a COVID-19 diagnosis.
• Stress. A review of 37 studies by Kim and colleagues found that HRV changed in response to stress in most of them, most often showing lower parasympathetic activity, the part of the nervous system that helps you rest.
• Measurement. Harvard Health says it is not clear how accurate wearable readings are, and Cleveland Clinic cautions that wrist trackers may not be sensitive enough to measure HRV accurately. A different time of day or device can also move the number.

One day or a trend

Researchers who monitor athletes, such as Plews and colleagues, favour looking at averages over a week or so rather than reacting to one morning’s figure. That is a useful habit for anyone.

A guide to thinking about readings, not a diagnostic chart.

What tends to help

Nothing on this page is a treatment, but the usual habits are the ones that matter. Harvard Health names chronic stress, poor sleep, lack of exercise and an unhealthy diet as things that can disrupt the balance of the nervous system. Regular sleep, recovery between hard sessions and a plan for stressful weeks are reasonable places to start. Give any new routine a few weeks before judging it.

When to talk to a doctor

A low HRV on a watch cannot diagnose a condition. Cleveland Clinic says low HRV can go along with heart conditions and mental health issues, and Harvard Health says low HRV is associated with a higher risk of cardiovascular disease across populations. That is a reason to take a lasting change seriously, not to panic over one reading.

The NHS says to see a GP if palpitations keep coming back or happen more often, last longer than a few minutes, or if you have a heart condition or a family history of heart problems. It says to call 999 or go to A&E if palpitations do not go away, or if you also have chest pain, shortness of breath or feel faint. If low mood or anxiety is behind a run of poor numbers, a GP is the right person to talk to as well.

Vital gives general information about fitness and wellbeing. It is not medical advice, and it does not diagnose or treat any condition.