Why is my HRV so low?
Often it isn’t low for you. Check the measurement first: which device, which number, and whether you switched. Then your age and fitness. Then the habits that pull it down night by night: drinks, smoking, late dinners, late hard workouts and short sleep.
The worry often starts with a comparison: a friend’s number, or a chart online. HRV researcher Marco Altini says the people who write to him worried typically report about 20 ms, which he calls normal in the fifties and common in younger adults. A low number that stays steady, dips after drinks and recovers after rest is a system that works.
What we’d do: find your own range from two to three weeks of nights on one device. Then explain only what’s new, a week that sits below that range.
The causes, measurement first
| Cause | How big | Study |
|---|---|---|
| Your device | Apple Watch about 8 ms under a chest strap. In athletes, an optical sensor gave 81 ms on average where an ECG gave 104 | 39 adults, 2024. 103 athletes, 2026 |
| Your age | RMSSD in the fifties about half of teenage values | 260 people, 1998 |
| Pregnancy | More than 15 ms lower by week 32 | 10,318 pregnancies, 2025 |
| Drinks | About 3 to 4 ms lower with one drink more than your usual, against one fewer | 20,968 people, 2026 |
| Tobacco | 3.5 ms lower after a day of tobacco use | 12,678 people, 2026 |
| Short sleep | RMSSD lower after sleep loss | 11 trials, 2025 |
| Late hard workouts | Lower that night. Workouts finished 4 or more hours before sleep weren’t linked to changes in sleep | 14,689 people, 2025 |
| Late dinners | Night HRV rose when the last meal came 3 or more hours before sleep | 39 adults, 2026 |
Fitness works the other way, slowly. In more than 8 million Fitbit users, people who took more steps a day had higher HRV at every age.
When is low a reason to see a doctor?
HRV on its own doesn’t diagnose anything. See a doctor for symptoms, whatever your number: chest pain, fainting, shortness of breath, or a racing or irregular pulse. When should I worry about low HRV? has the full list.
Connect your ring or watch, and Gyroscope shows every night’s HRV against your own normal, with your sleep and drinks right beside it. Track it.
11 sources
- Altini M, Low heart rate variability (HRV), 2023marcoaltini.substack.com
- O'Grady B et al., The validity of Apple Watch Series 9 and Ultra 2 for serial measurements of heart rate variability and resting heart rate, Sensors, 2024pmc.ncbi.nlm.nih.gov
- Ben-David K et al., Pulse rate variability is not the same as heart rate variability, Sports Medicine Open, 2026pubmed.ncbi.nlm.nih.gov
- Umetani K et al., Twenty-four hour time domain heart rate variability and heart rate: relations to age and gender over nine decades, Journal of the American College of Cardiology, 1998pubmed.ncbi.nlm.nih.gov
- Adaimi R et al., Temporal trajectories in sleep, temperature trends, cardiorespiratory, and activity metrics measured via Oura Ring during pregnancy, JMIR mHealth and uHealth, 2025pubmed.ncbi.nlm.nih.gov
- Grosicki GJ et al., Real-world effects of alcohol on heart rate, sleep, and physical activity by age and sex, PLOS Digital Health, 2026pubmed.ncbi.nlm.nih.gov
- Curran DJ et al., Tobacco use trajectories and associated changes in biometrics and sleep during the first 72 weeks of wearable membership, JMIR mHealth and uHealth, 2026pubmed.ncbi.nlm.nih.gov
- Zhang S et al., Effects of sleep deprivation on heart rate variability: a systematic review and meta-analysis, Frontiers in Neurology, 2025pubmed.ncbi.nlm.nih.gov
- Leota J et al., Dose-response relationship between evening exercise and sleep, Nature Communications, 2025pubmed.ncbi.nlm.nih.gov
- Grimaldi D et al., Sleep-aligned extended overnight fasting improves nighttime and daytime cardiometabolic function, Arteriosclerosis, Thrombosis, and Vascular Biology, 2026pubmed.ncbi.nlm.nih.gov
- Natarajan A et al., Heart rate variability with photoplethysmography in 8 million individuals: a cross-sectional study, Lancet Digital Health, 2020pubmed.ncbi.nlm.nih.gov
