You opened the Health app, saw an HRV of 22 ms, googled "normal HRV," found a chart saying healthy people are at 60+, and now you're worried. This exact sequence happens thousands of times a day — and in almost every case, the worry is misplaced. Here's what's actually going on.
The short answer
A low heart rate variability reading on Apple Watch is most often caused by one or more of the following: acute stress, poor or short sleep, alcohol the night before, illness (often before symptoms appear), hard exercise in the previous 24–48 hours, dehydration, or simply when the measurement was taken. HRV also naturally declines with age and runs lower in some perfectly healthy people. A single low number tells you almost nothing; a sustained drop below your own baseline tells you your body is under load.
Why the number swings so much
Apple Watch samples HRV opportunistically throughout the day and night, not under a controlled protocol. HRV measured mid-afternoon after coffee and a tense meeting can be a third of the value measured during deep sleep. That's not your watch being inaccurate — validation studies show Apple Watch HRV tracks closely with ECG at rest — it's the metric doing exactly what it's supposed to do: reflecting your nervous system's state in the moment.
This is why comparing your daily average to a chart on the internet is nearly meaningless. You're comparing an uncontrolled sample of your day against population statistics gathered under different conditions.
What low HRV actually reflects
HRV measures the tiny variations in time between heartbeats. Those variations are controlled by your autonomic nervous system — the balance between the sympathetic ("fight or flight") and parasympathetic ("rest and digest") branches. When your body is under load — psychological stress, sleep debt, infection, recovery from training, alcohol metabolism — sympathetic tone rises, the heart beats more metronomically, and HRV falls.
In other words: low HRV is a load gauge, not a damage gauge. It's your physiology saying "resources are being spent," which is often appropriate and temporary.
The common causes, ranked by how often I see them
- Stress. The single most common driver. HRV frequently drops a day or two before people consciously register that they're stressed.
- Sleep. Short, fragmented, or late sleep reliably suppresses next-day HRV.
- Alcohol. Even two drinks can depress overnight HRV measurably; it's one of the most consistent findings in wearable data.
- Illness. HRV often dips before you feel sick — your immune system spending resources.
- Training load. A hard workout suppresses HRV for 24–48 hours. That's normal recovery, not a problem.
- Measurement timing. Daytime spot readings run much lower than sleep readings.
When low HRV is worth mentioning to a doctor
If your HRV is persistently very low relative to your history and accompanied by symptoms — palpitations, unusual fatigue, chest discomfort, fainting — bring it up with a clinician. Certain conditions (dysautonomia, arrhythmias, poorly controlled diabetes, anxiety and depression) are associated with reduced HRV. But the wearable number itself is not a diagnosis; it's a conversation starter.
What to do instead of worrying
- Establish your baseline. Two to three weeks of data gives you a personal normal. Everything after that is measured against you, not a chart.
- Watch trends, not days. A multi-day slide below baseline means your body is asking for recovery: sleep, lighter training, less alcohol, stress management.
- Connect it to how you feel. HRV becomes genuinely useful when paired with mood data. A low-HRV morning that precedes an irritable, anxious day — repeatedly — is a pattern you can plan around. That connection between physiology and emotion is exactly what MoodQuad was built to surface. (More on the science in our guide to HRV and mood.)
Put this into practice with MoodQuad
MoodQuad reads your HRV from Apple Health, learns your personal baseline, and connects it to how you actually feel on the Mood Map — so a low number becomes information instead of anxiety. Free to start, fully private, on-device.
Medical disclaimer: This article and the MoodQuad app are for education and self-reflection only. They do not provide medical advice, diagnosis, or treatment. HRV and heart rate data from consumer wearables are not diagnostic. If you have concerns about your heart or mental health, talk to a qualified clinician. If you are in crisis in the US, call or text 988.