Low HRV: causes and how to raise it
Compare it with your own usual first. Short sleep, alcohol and stress can all pull it down. And a free habit, slow breathing, raised HRV in a review of 223 studies.
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What counts as low HRV?
No health body sets a cut-off. A 2010 review of 44 studies said there were no agreed normal values for short HRV readings. Some studies found big differences between healthy people.
HRV also falls with age. Healthy adults lay still for a 5-minute heart trace measuring RMSSD, the HRV measure most studies here use. The average was about 40 ms (milliseconds) at 25 to 34 and about 20 ms at 55 to 64.
So a reading of 25 is a little above average at 60 but below average at 30. Low matters most when it’s low for you.
Is your HRV really low? Check in this order
- 1
Same time, same device
HRV swings across the day. Measure at the same time each day.
- 2
Your own usual
Compare with your own past readings, not a friend’s.
- 3
Your age
Then compare with averages for your age. About 20 is average at 55 to 64.
- 4
The night before
Look back. Short sleep, drinks or a stressful day?
Sources: Fitbit study; Voss 2015
The full table for women and men is in our guide to normal HRV by age. Check it, then look at your last week of readings.
What causes low heart rate variability?
Most studies below report RMSSD, the change in time from one heartbeat to the next. It mainly tracks the nerve that slows your heart (the vagus nerve), the calming side of your nervous system.
| Cause | What studies found | What to try |
|---|---|---|
| Short sleep | In 11 trials with 549 people, cutting sleep lowered RMSSD. | Go to bed and get up at similar times each day. |
| Alcohol | 4,098 workers had lower RMSSD on nights they drank. | Avoid alcohol 1 to 2 hours before bed. |
| Stress | In most of 37 studies, HRV changed under stress. A drop in the calming side was the most common finding. | Slow breathing (see below). |
| Little activity | Fitbit users who moved more tended to have higher HRV. | Build up to 150 minutes of moderate activity a week. |
| Age | Average RMSSD roughly halves from age 25 to 34 to age 55 to 64. | Compare with people your age. |
Sources: Sleep trials review 2025; Pietilä 2018; Kim 2018; Fitbit study; Voss 2015; NHS
Sleep? The review of sleep loss trials found RMSSD dropped. Other HRV measures moved less clearly, and the authors call for better studies.
Stress? A review found HRV changed in response to stress in most studies. For practical steps, see how to reduce stress.
Pick the row that fits your week and start there.
Can one night of drinking lower HRV?
Yes, in a big real-world study. Researchers in Finland compared each of 4,098 workers’ drinking and non-drinking nights. They looked at the first 3 hours of sleep.
| Alcohol that evening | For someone weighing 70 kg | Fall in RMSSD |
|---|---|---|
| Low: up to 0.25 g per kg | Up to about 2 units | 2.0 ms |
| Moderate: 0.25 to 0.75 g per kg | About 2 to 6.5 units | 5.7 ms |
| High: more than 0.75 g per kg | More than about 6.5 units | 12.9 ms |
Fit or young? The researchers say regular exercise and young age did not protect against the effect. It was a study of habits, not a trial, so it shows a link.
The NHS says drinking more than 14 units a week regularly risks your health. Read more on alcohol and sleep, then try a dry week and watch your readings.
How can I increase my HRV?
Start with slow breathing. A review of 223 studies found HRV went up during slow breathing, just after one session, and after a course of several sessions. The authors expect few side effects.
The biggest effect usually comes at about 6 breaths a minute. That’s about 5 seconds in and 5 seconds out.
Exercise helps too. In 16 trials with 623 healthy adults, exercise training raised RMSSD. The authors note there are few trials so far.
Five things to try for a low HRV
- Breathe slowly for at least 5 minutes a day, as in the NHS breathing exercise. Count from 1 to 5 as you breathe in, and 1 to 5 as you breathe out.
- Build up to at least 150 minutes of moderate activity a week, or 75 minutes of vigorous activity.
- Go to bed and get up at similar times each day.
- Avoid alcohol 1 to 2 hours before bed, and keep to 14 units a week or less.
- Measure at the same time of day on the same device, and compare with your own past readings.
Sources: NHS: breathing; NHS: activity; NHS: sleep; NHS: alcohol; Fitbit study
New to exercise? Start with zone 2 training, steady exercise you can talk through. The NHS asks for 150 minutes a week, spread over 4 to 5 days or more.
Should I worry about low HRV?
Judge one low day against your usual. Long term, low HRV is linked to heart risk. Eight studies of 21,988 people found low HRV was linked to a 32% to 45% higher risk of a first heart or circulation problem.
That’s a link, not proof that low HRV causes it. Those studies used ECG heart traces, not watches.
Low HRV symptoms? We found no NHS or BHF page that lists any. Go by how you feel and your pulse instead.
Watches are not medical devices, the British Heart Foundation (BHF) says, and checking them can increase health anxiety. Our guide to tracker accuracy explains why.
Check your pulse by hand if a reading worries you.
When to speak to a GP
There’s no warning level for HRV on NHS or BHF pages. See a GP if:
- Your pulse is slow and you feel faint or have fainted, feel very tired, or feel dizzy. That’s the BHF’s advice.
- Your heart beats fast for no obvious reason or when you’re at rest.
- Your pulse feels irregular. It could be a sign of an abnormal heart rhythm such as atrial fibrillation (AF), which is more likely if you’re 65 or older.
- You have palpitations (your heartbeat feels racing, pounding, fluttering or irregular) that keep coming back, happen more often or last more than a few minutes. Also if you have a heart condition or heart problems run in your family. That’s NHS advice.
- Your HRV numbers or trends worry you. The BHF says to let your doctor or nurse know.
Call 999 or go to A&E if you have palpitations that don’t go away, or with chest pain, shortness of breath, feeling faint or fainting. Don’t drive yourself. Ask someone to drive you or call 999.
If those symptoms have stopped, ask your GP surgery for an urgent appointment or call 111. See also blood tests for palpitations.