Usually because of who you are and how you measure. An HRV that has always sat below the charts mostly reflects your age, your genes, your resting heart rate Resting heart rate How many times your heart beats per minute while you are fully at rest. For adults it is usually 60 to 100 beats per minute, and lower in well-trained athletes. More about Resting heart rate and the device and measure you use. A sudden drop from your own usual range is a different question, and it usually points to recent strain such as short sleep, alcohol, hard training or an illness starting.
Always low or suddenly low?
The two look alike in an app and mean different things.
| Suddenly low | Always low | |
|---|---|---|
| What you see | A dip below your own usual range | Your usual range itself sits below a chart or a friend’s number |
| Usual causes | Short sleep, alcohol, hard training, illness, stress | Age, genes, measure and device, a fast resting heart rate, fitness, some medicines |
| What helps | Look back over the last 48 hours and watch the next few days | Compare with the right norms, then follow your own trend |
The size of a sudden dip is modest. In 28,175 people who took a short phone reading each morning, HRV was about 10% lower on sick days and about 12% lower after heavy drinking, each person compared with their own average (Altini and Plews, 2021). What does a low HRV mean? covers dips. This page is about the level.
Age lowers the level for everyone
HRV falls through adult life. In 1,906 healthy adults measured with a 5-minute ECG ECG A recording of the heart's electrical activity, taken with electrodes on the skin. ECG-based RR intervals are the reference standard for measuring HRV. More about ECG lying down, median RMSSD RMSSD Root mean square of successive differences: an HRV metric built from how much each heartbeat interval differs from the next, in milliseconds. It mainly reflects vagal activity. More about RMSSD was 38.4 ms in women and 36.2 ms in men aged 25 to 34, and 16.9 ms and 16.7 ms at 65 to 74 (Voss and colleagues, 2015). That is a fall of more than half. In 24-hour recordings from 260 healthy people, RMSSD in people in their 50s was 47% of the value in 10- to 19-year-olds, and then it levelled off (Umetani and colleagues, 1998).
So a 55-year-old who compares themselves with a chart built on 30-year-olds will always look low. The tables on normal HRV by age are split by age and sex, and can HRV improve after 60? covers the later decades.
Genes and the spread between healthy people
Even at the same age, healthy people differ a lot. Among women aged 25 to 34 in the Voss study, a quarter had an RMSSD below 26.1 ms and a quarter above 54.5 ms. Everyone in those tables was healthy, including the bottom quarter.
Much of that spread is inherited. In 772 twins and siblings who wore 24-hour heart monitors, genes explained 40 to 48% of the differences in RMSSD between people (Kupper and colleagues, 2004). In the app study, age, sex, activity and body mass index together explained only about 15% of the differences between people. The rest is mostly the make-up of each person’s nervous system, which is why is HRV genetic? concludes that your own trend says more than any comparison.
Sex and body weight
Differences between women and men are small and depend on the measure. A meta-analysis of 63,612 people found that women had, on average, a slightly lower SDNN SDNN The standard deviation of all NN intervals in a recording, in milliseconds. It measures overall variability, and its value depends strongly on how long the recording lasts. More about SDNN but more high-frequency power HF power The variance of the heartbeat intervals that falls in the 0.15 to 0.40 Hz band, in ms²: the range of normal breathing. It mainly reflects vagal activity when breathing is 9 to 24 breaths a minute. More about HF power , a vagal measure, than men (Koenig and Thayer, 2016). In the app study, average RMSSD was almost the same for both.
Carrying extra weight tends to go with lower HRV. A 2024 review lists overweight among the lifestyle factors linked with lower values (Sammito and colleagues, 2024), and in a 2022 review, most of 12 studies found a shift toward the calming side of the nervous system after weight loss through diet, exercise or both (Mattos and colleagues, 2022). The page on losing weight has the details.
Your resting heart rate
HRV and heart rate are tied together by arithmetic as well as by the nervous system. At 60 beats a minute the average gap between beats is 1,000 ms; at 120 it is 500 ms. The same small wobble in heart rate makes bigger changes in the gaps when the heart is slow, which is one reason HRV tends to be higher when resting heart rate is lower (Sacha, 2014). If your resting pulse has always been on the high side, your HRV will tend to sit lower. HRV vs resting heart rate shows the numbers.
Fitness, and the fit person’s puzzle
Fitness helps, within limits. Pooling 13 training studies with 322 people, Sandercock and colleagues found a moderate rise in high-frequency HRV (d = 0.48) and a larger lengthening of the gap between beats (d = 0.75) (Sandercock and colleagues, 2005). The heart slowed more reliably than HRV rose.
Very fit people can read low for a different reason. When the heart is very slow, the fast, breathing-linked swings (high-frequency power, which RMSSD largely tracks) stop growing: in 24-hour recordings, 35 of 76 healthy people showed this levelling off (Kiviniemi and colleagues, 2004). Why is my HRV low even though I’m very fit? explains it, and does HRV go up when I get fitter? gives the expected sizes.
Medicines
Some medicines set a lower or higher level for as long as you take them. Tricyclic antidepressants lower HRV (Kemp and colleagues, 2010). Stimulants for ADHD raised resting heart rate by about 6 beats a minute in adults (Mick and colleagues, 2013), and GLP-1 drugs such as semaglutide raised it by about 3.5 beats a minute against placebo (Zhang and colleagues, 2026); a faster heart tends to go with a lower HRV. Beta-blockers tend to do the opposite: in a scoping review of trials in people with high blood pressure, they were the drugs most consistently linked with improved HRV, though not in every trial (Sehgal and colleagues, 2025).
None of this is a reason to change a dose. Never stop, start or change a medicine because of your HRV; talk to your doctor or pharmacist. Do medications affect HRV? has the full table.
Your device and your measure
Many “always low” numbers are a comparison between different things.
- Different statistics. Apple Health stores Apple Watch HRV as SDNN, while most rings and bands report RMSSD. SDNN also grows with recording length, and the 1996 standards warn against comparing SDNN from recordings of different lengths (Task Force, 1996). See why Apple Watch HRV is different.
- Different times. HRV changes a lot through the day and night. In wrist data from 8,203,261 Fitbit users, the authors needed separate benchmark tables for two times of day (Natarajan and colleagues, 2020). An overnight average and a 5-minute morning reading are not the same number, as overnight vs morning HRV explains.
- Different sensors. In 13 adults followed for 536 nights, ring and wrist devices had average overnight RMSSD errors from 5.96% to 16.32% against a chest-strap ECG (Dial and colleagues, 2025). Two devices on the same night can disagree; HRV by device shows how each one measures.
The clinical charts on this site come from 5-minute ECG readings lying down after rest. If your number comes from a watch at night, compare it with your own past nights first.
When a low level is worth a doctor’s visit
A number that has always been low, with no symptoms, is not a reason to see a doctor on its own, and HRV cannot diagnose anything. Talk to a doctor when:
- Your own level has changed. Your HRV used to sit higher and has stayed well below that range for weeks, with no clear reason such as sleep, training, stress or illness, especially if it comes with lasting tiredness, low mood or poor sleep.
- You feel faint or dizzy when you stand up. Light-headedness, weakness, palpitations or faintness on standing are worth checking. The American Diabetes Association lists them as the most common symptoms of nerve damage to the heart in diabetes (Pop-Busui and colleagues, 2017).
- Your heartbeat feels wrong. You often feel extra beats, notice new palpitations, or have a resting pulse over 100 that exercise, anxiety or fever does not explain (MedlinePlus).
Get emergency help for chest pain, fainting or trouble breathing, whatever your HRV shows. Bring your trend data to the appointment and let the doctor decide what tests you need.