How do I know if my HRV is low?

Compare it with your own usual range on the same device, built from two to three weeks of nights. Then watch the 7-day average, not single nights. A week below your range is worth acting on. One low night usually has a cause you can name.

An age chart or a friend’s number can’t tell you whether yours is low. Your own last few weeks can.

Why does an age chart say my HRV is bad?

Because the chart wasn’t made for you. Age tables online come from different devices, different calculations and different times of day, and most don’t say which. A number in the 30s can be low on one chart and normal on another.

Even good figures only describe a crowd. Across 6 million Oura members in 2026, the average was 41 ms and the median was 35 ms for men and 36 ms for women, so about half of all members sat below the mid-30s. HRV also falls with age: in one study of healthy people, RMSSD in the 50s was 47 percent of its value in the teens. None of that tells you whether your number is low for you.

Garmin’s own guide puts it plainly: “Your own personal history, then, is the single-most meaningful frame of reference for interpreting HRV data.”

A simple way to picture it

Think of weighing yourself. Your weight jumps a pound or two from one morning to the next, from water, salt and what you ate late. Nobody panics at one morning. You watch the trend over a week or two, and you only compare with yourself on your own scale.

HRV works the same way, with bigger daily jumps. The night is noise. The week is the signal.

How do I build my own normal range?

1. Pick one device and wear it every night. Same wrist or finger, same fit.
2. Give it two to three weeks. Garmin needs about three weeks of nights before HRV Status starts, and can use a few months to firm up the range. Apple’s Vitals app asks for 7 nights to set a typical range. WHOOP’s data carries a flag for a member who is still calibrating.
3. Use the overnight average. Not the night’s maximum, and not daytime samples.
4. Find your usual band. Roughly, the range most of your nights fall in. Garmin shows this as a band, such as 33 to 45 ms. Our normal range calculator works it out from your nights.
5. Track the 7-day average against the band. Missing a night or two is fine. A 2026 study of WHOOP data found five of seven nights gave a reliable picture of how much a week varied.
6. Let the band move. Your normal shifts with fitness, seasons, age and life. Garmin’s baseline “is not static and will shift over time.”

The model breaks down when the measurement changes. A new device, a new model or a new wear spot starts a new band, and comparing across the change will mislead you.

Why the 7-day average and not last night?

Moderate The weekly average is the better guide. The best direct evidence is small, but it all points the same way.

When does a drop matter?

The two-night rule comes from the first HRV training trial. In 2007, 26 men took part over four weeks. The HRV group, measured every morning on the breathing-linked part of HRV, trained hard when it held up, and easy when it fell below their own 10-day average minus one standard deviation or dropped two days in a row. They improved their top running speed more than a group on a fixed plan.

The size of the drop that counts depends on you, which is why your band matters. As a sense of scale, in 20,968 WHOOP members, one drink above your usual against one below came with HRV 3.3 to 3.8 ms lower. A maximal workout ending two hours before bed came with HRV 8.3 ms lower than a light one.

Is a high HRV ever a warning?

Sometimes. A 2016 review of 27 training studies found resting RMSSD rose a little even in athletes who were overreaching and getting slower. Garmin’s Unbalanced status covers an average above your band as well as below it for this reason. And irregular beats from an arrhythmia look like variation to a sensor, so a sudden high night with symptoms is a reason to see a doctor.

Should I go by how I feel instead?

Use both, and expect them to disagree. In 39 adults tracked for three months, how stressed or nervous people said they felt had no link with their overnight HRV, and days they felt energized came with slightly lower HRV. Your number and your feelings are two different signals.

When should I see a doctor?

HRV can’t diagnose anything, and a normal number doesn’t rule anything out. See a doctor if you have chest pain, faint, feel your heart racing or skipping, or feel unwell for more than a few days, whatever your device says.