What is a normal HRV range?

Adult HRV commonly spans roughly 20 to 120 milliseconds, and where you sit depends heavily on age, genetics, and fitness. A 35 can be perfectly normal for one person and a warning sign for another. The number that matters is your own baseline: a stable or rising trend is good news at any absolute level.

How fast can HRV improve?

Overnight dips from alcohol, a late meal, or one hard workout usually rebound in 1 to 3 days. Raising your actual baseline is slower: consistent sleep timing and aerobic base training typically need several weeks to a few months to show up as a durable upward trend.

Should I compare my HRV to other people?

No, and this is one of the few flat answers in wearable land. HRV varies several-fold between healthy adults for reasons that have nothing to do with fitness, including genetics and age. Compare this month's baseline to last month's baseline and ignore everyone else's number.

Why Is My HRV Low? 9 Causes Ranked From Fix-It-Tonight to See-a-Doctor

Your HRV dropped and you want to know why. The short answer: the most common causes are alcohol, poor sleep, a hard workout, stress, or an incoming illness, and most of them resolve on their own within 1 to 3 days. A low reading this morning is usually your body mid-repair, and only a sustained unexplained decline is worth a doctor's visit.

Quick refresher before the list: HRV is the variation in time between heartbeats, WHOOP measures it overnight during sleep, and it scores you against your own rolling baseline. Higher variability generally reflects a rested, adaptable nervous system. Lower reflects a system under load, from any source.

Here are the 9 causes, ranked from fastest to fix to slowest.

The 9 causes of low HRV, ranked by how fast you can fix them

Rank	Cause	Typical rebound
1	Alcohol last night	1 to 2 days
2	Late heavy meal	1 day
3	Poor or short sleep	1 to 2 good nights
4	Hard training	1 to 3 days
5	Acute stress	Days, once the stressor eases
6	Dehydration or heat	1 to 2 days
7	Incoming illness	Days to a week or more
8	Chronic overtraining	Weeks
9	Persistent unexplained decline	See a doctor

1. Alcohol last night (fix: tonight)

Mechanism: alcohol suppresses parasympathetic activity and elevates heart rate for much of the night while your body metabolizes it. What to do: nothing needed, hydrate, and skip drinks tonight. Rebound: usually 1 to 2 days, and yes, the effect scales with dose. We ran the numbers on what drinking does to WHOOP recovery if you want the ugly details.

2. A late heavy meal (fix: tonight)

Mechanism: digestion keeps your metabolic and cardiac workload elevated into the night, right when HRV is measured. What to do: finish your last big meal about 3 hours before bed. Rebound: next morning, which makes this one of the cheapest experiments in this whole list.

3. Poor or short sleep (fix: 1 to 2 nights)

Mechanism: sleep is when parasympathetic recovery happens, so cutting sleep cuts the recovery window itself. What to do: protect tonight ruthlessly, consistent bedtime, dark cool room, no doomscrolling in bed. The CDC's sleep guidance starts at 7 hours for adults for a reason. Rebound: often one good night, reliably two.

4. Hard training (normal, temporary)

Mechanism: a big session is deliberate stress, and your nervous system stays in repair mode overnight. This dip is the plan working. What to do: easy day today, real sleep tonight. Rebound: 1 to 3 days depending on the session. If you are unsure how to structure the easy day, here is exactly what to do on a low recovery day.

5. Acute stress (fix: days, honestly)

Mechanism: psychological stress runs the same sympathetic machinery as physical stress, so deadlines and arguments show up in heartbeat data. What to do: you cannot delete the stressor, but slow breathing sessions, walks, and keeping training easy all reduce the total load. Rebound: tracks the stressor, typically days.

6. Dehydration or heat (fix: 1 to 2 days)

Mechanism: lower blood volume makes your heart work harder to move the same oxygen, which reads as strain to your nervous system. Hot bedrooms pile on. What to do: rehydrate through the day (steadily beats chugging), and aim for a cool room, somewhere around 65 to 68 F. Rebound: fast, usually a day or two.

7. Incoming illness (fix: wait it out)

Mechanism: your immune system mounting a response is metabolically expensive, and HRV often drops 1 to 2 days before you feel symptoms. What to do: if HRV tanks with no obvious cause, treat yourself as possibly sick: easy day, early night, hydration. Rebound: days to a week or more. This early-warning behavior is genuinely one of the most useful things a wearable does.

8. Chronic overtraining (fix: weeks)

Mechanism: weeks of hard training without adequate recovery leaves the stress response chronically switched on, and baseline HRV grinds downward. What to do: a real deload, 1 to 2 weeks of easy volume, plus a hard look at sleep and life stress. Rebound: weeks, and pushing through it extends the bill.

9. Persistent unexplained decline (talk to a doctor)

If your HRV baseline has been sliding for weeks and none of the above applies, that is a conversation for a physician. A wearable measures trends in your data. It cannot diagnose anything, and a sustained unexplained change in cardiac data is exactly the kind of thing worth showing to someone with a medical license. Low drama, just do it.

What is a normal HRV? (Read this before you panic)

HRV is deeply individual. Across healthy adults, overnight HRV commonly spans roughly 20 to 120 milliseconds, driven by age, genetics, and fitness, which means comparing your number to a friend's tells you almost nothing. A fit 45-year-old at 40ms and a 25-year-old at 90ms can both be thriving. The standard reference here is this overview of HRV metrics and norms, and its core message matches WHOOP's design: the meaningful signal is your trend against your own baseline. A stable or slowly rising baseline is winning, at any absolute number.

So retire the question "is 35 bad" and replace it with "is my 35 normal for me, and which direction is it drifting."

How do you actually raise your baseline HRV?

The stuff research consistently supports is boring and works:

A consistent sleep schedule. Same bedtime and wake time daily. This is the highest-leverage habit on the list, and we broke down the full stack in how to improve your WHOOP recovery.
Aerobic base training. Regular zone 2 work is one of the best-documented drivers of higher resting HRV over months.
Less alcohol. The single fastest subtraction. Every drink-free week is a small deposit in the baseline.
Stress work. Slow breathing and meditation have real, measurable effects on HRV. The honest framing: the effects are modest, and they compound with everything above rather than replacing it.

Timeline expectations: weeks to months for a baseline shift. Anyone promising a doubled HRV in ten days is selling something.

One last practical note. Most HRV dips resolve before you would ever have noticed them, and the few that matter (the pre-illness drop, the overtraining slide) matter precisely because you catch them the morning they start. PulseCheck watches your WHOOP data for exactly those meaningful dips and flags them in a morning notification with an actual personality, which means the warning gets read instead of buried in a chart you stopped opening in March.

Tonight's checklist

Figure out which of the 9 fits this morning's dip. Usually it is in the top 4.
If the cause is obvious: hydrate, eat earlier, skip the drink, sleep on schedule.
If there is no obvious cause: treat today as a maybe-sick day and go easy.
Judge the trend over 3 to 7 days, never a single morning.
Weeks of unexplained decline: book the doctor and bring the data.

Your HRV is a smoke detector. Most beeps are burnt toast. Learn which beep is which and it becomes the most useful number on your wrist.